MAX16816ATJ [MAXIM]
Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming; 可编程开关模式LED驱动器，提供模拟控制的PWM调光
| 型号： | MAX16816ATJ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming |
| 文件： | 总33页 (文件大小：342K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1054; Rev 0; 1/08
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
General Description
Features
o EEPROM-Programmable LED Current Binning
The MAX16816 is a current-mode, high-brightness LED
(HB LED) driver designed to control two external
n-channel MOSFETs for single-string LED current regu-
lation. The MAX16816 integrates all the building blocks
necessary to implement fixed-frequency HB LED dri-
vers with wide-range dimming control and EEPROM-
programmable LED current binning with a factor of up
to 1.6. This device is configurable to operate as a step-
down (buck), step-up (boost), or step-up/step-down
(buck-boost) current regulator.
o Wide Input Range: 5.9V to 76V with Cold Start
Operation to 5.4V
o Integrated Floating Differential LED Current-
Sense Amplifier
o Floating Dimming Driver Capable of Driving an
n-Channel MOSFET
o 5% or Better LED Current Accuracy
o Multiple Topologies: Buck, Boost, Buck-Boost,
SEPIC
Current-mode control with adjustable leading-edge
blanking simplifies control-loop design. Adjustable slope
compensation stabilizes the current loop when operating
at duty cycles above 50%. The MAX16816 operates over
a wide input voltage range and is capable of withstand-
ing automotive load-dump events. Multiple MAX16816
devices can be synchronized to each other or to an
external clock. The MAX16816 includes a floating
dimming driver for brightness control with an external
n-channel MOSFET in series with the LED string.
o Resistor-Programmable Switching Frequency
(125kHz to 500kHz) and Synchronization
Capability
o 200Hz On-Board Ramp Allows Analog-Controlled
PWM Dimming and External PWM Dimming
o Output Overvoltage, Overcurrent, and LED Short
Protection
o Enable/Shutdown Input with Shutdown Current
Below 45µA
HB LEDs using the MAX16816 can achieve efficiencies
of over 90% in automotive applications. The MAX16816
also includes a 1.4A source and 2A sink gate driver for
driving switching MOSFETs in high-power LED driver
applications, such as front light assemblies. Dimming
control allows for wide PWM dimming range at frequen-
cies up to 5kHz. Higher dimming ratios (up to 1000:1)
are achievable at lower dimming frequencies.
Ordering Information
PIN-
PACKAGE
PKG
CODE
PART
TEMP RANGE
MAX16816ATJ+ -40°C to +125°C 32 TQFN-EP* T3255M-4
+Denotes a lead-free package.
*EP = Exposed pad.
Pin Configuration appears at end of data sheet.
The MAX16816 provides user-programmable features
through on-chip nonvolatile EEPROM registers.
Adjustable features include a programmable soft-start,
LED current (binning), external MOSFET gate driver sup-
ply voltage, slope compensation, leading-edge blanking
time, and disabling/enabling of the RT oscillator.
Typical Operating Circuits
BUCK-BOOST CONFIGURATION
V
IN
R
CS
C
CLMP
R
UV2
The MAX16816 is available in a 32-pin TQFN package
with exposed pad and operates over the -40°C to
+125°C automotive temperature range.
CS+
V
LO
CLMP
CS-
DGT
CC
R
UV1
Q
R
S
UVEN
D
DRV
C
UVEN
LEDs
SNS+
Applications
R
SENSE
DIM
DIM
SNS-
Automotive Exterior: Rear Combination Lights
(RCL), Daytime Running Lights (DRL), Fog and
Front Lighting, High-Beam/Low-Beam/Turn Lights
QGND
REG1
MAX16816
C
REG1
HI
R
T
C
F
RTSYNC
R
OV1
FAULT
COMP
R1
General Illumination
OV
REG2
CS
FB
AGND
SGND
DRI
R
OV2
Navigation and Marine Indicators
Neon Replacement, Emergency Lighting
Signage and Beacons
C
REG2
C2
R2
C1
Typical Operating Circuits continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
ABSOLUTE MAXIMUM RATINGS
CC
CS+, CS-, DGT, UVEN, FAULT to QGND...............-0.3V to +80V
UVEN to QGND ..........................................-0.3V to (V + 0.3V)
V
, HI, LO, CLMP to QGND.................................-0.3V to +80V
CS+, CS-, DGT, CLMP to LO ........................-0.3V to (HI + 0.3V)
HI to CLMP .............................................................-0.3V to +28V
Continuous Power Dissipation* (T = +70°C)
CC
A
DRV to SGND .........................................................-0.3V to +18V
DRI, REG2, DIM to AGND ......................................-0.3V to +18V
QGND, SGND to AGND ........................................-0.3V to +0.3V
SNS+ to SNS-...........................................................-0.3V to +6V
CS, FB, COMP, SNS+, SNS-, OV, REF,
RTSYNC to AGND ................................................-0.3V to +6V
REG1, CLKOUT to AGND ........................................-0.3V to +6V
CS+ to CS- .............................................................-0.3V to +12V
HI to LO ..................................................................-0.3V to +36V
CS+, CS-, DGT, CLMP to LO .................................-0.3V to +12V
32-Pin TQFN (derate 34.5mW/°C above +70°C) .......2758mW
Thermal Resistance
θ
θ
................................................................................29°C/W
...............................................................................1.7°C/W
JA
JC
Operating Temperature Range .........................-40°C to +125°C
Maximum Junction Temperature .....................................+150°C
Storage Temperature Range.............................-60°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
MAX816
*As per JEDEC 51 standard, Multilayer Board (PCB).
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
= V
= 14V, C
= 1µF, C
= 1µF, C
= 0.1µF, R = 25kΩ, T = T = -40°C to +125°C, unless otherwise noted.
CC
UVEN
REG1
REG2
CLMP
T
A
J
Typical specifications are at T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
76
UNITS
V
Input Voltage Range
V
5.5
CC
Q_VCC
Supply Current to V
I
Exclude current to the gate driver, I
2.7
0.5
25
1
4.5
1.0
45
mA
mA
µA
CC
REG2
Supply Current to HI
I
V
V
V
= 14V
HI
Q_HI
SHDN_VCC
Shutdown Current to V
I
≤ 300mV
≤ 300mV
CC
UVEN
UVEN
Shutdown Current to HI
I
10
µA
SHDN_HI
UVEN
V
V
V
V
rising
5.5
5.0
6.0
5.5
CC_R
CC
CC
V
V
UVLO Threshold
V
V
V
CC
CC
falling
CC_F
Threshold Hysteresis
V
0.4
CC_HYS
V
V
V
rising
1.10
1.00
1.244
1.145
1.36
1.26
UVR
UVEN
UVEN
UVEN Threshold
V
falling
UVF
(V
and V
= 0V and V
= 14V) (V
= 76V
UVEN
CC
UVEN
UVEN Input Current
REGULATORS
I
-0.2
+0.2
µA
V
UVEN
= 77V)
CC
0 < I
< 2mA, 7.5V < V
< 76V
4.75
4.00
5.00
4.50
0.5
5.25
5.25
1.0
REG1
CC
REG1 Regulator Output
V
REG1
I
I
= 2mA, V
= 5.7V
REG1
REG1
CC
REG1 Dropout Voltage
REG1 Load Regulation
= 2mA (Note 1)
= 0 to 2mA
V
ΔV/ΔI
V
= 7.5V, I
25
Ω
CC
REG1
V
≥ 9.5V, REG2 control register is ‘0011’,
= 20mA (Note 1)
CC
REG2 Dropout Voltage
REG2 Load Regulation
0.5
1.0
25
V
I
REG2
V
≥ 9.5V, REG2 control register is ‘0011’,
= 0 to 20mA
CC
ΔV/ΔI
Ω
I
REG2
2
_______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 14V, C
= 1µF, C
= 1µF, C
= 0.1µF, R = 25kΩ, T = T = -40°C to +125°C, unless otherwise noted.
CC
UVEN
REG1
REG2
CLMP
T
A
J
Typical specifications are at T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
REG2 control register is ‘0000’,
≥ 7.5V, I = 1mA
4.75
5
5.25
V
CC
REG2
REG2 control register is ‘0011’,
≥ 9.5V, I = 1mA
6.65
13.5
4
7.0
15
4.5
5
7.35
16.5
5.25
5.25
16.5
V
CC
REG2
REG2 control register is ‘1111’,
≥ 17.5V, I = 1mA
V
CC
REG2
REG2 Regulation Voltage
V
REG2 control register is ‘0000’,
= 5.7V, 0 ≤ I ≤ 20mA
V
CC
REG2
REG2 control register is ‘0000’,
= 7.5V, 0 ≤ I ≤ 20mA
4.75
13.5
V
CC
REG2
REG2 control register is ‘1111’,
= 17.5V, 0 ≤ I ≤ 20mA
15
V
CC
REG2
HIGH-SIDE REGULATOR (CLMP) (All voltages referred to V ) (Note 2)
LO
CLMP UVLO Threshold
V
V
rising
CLMP
2.0
5.5
2.5
0.22
8.0
3.0
V
V
CLMP_TH
CLMP UVLO Threshold
Hysteresis
V
CLMP_HYS
8.7V ≤ (V - V ) ≤ 36V, I = 1mA
CLMP
10.0
HI
LO
CLMP Regulator Output
Voltage
V
V
CLMP
(V - V
)
HI
LO
5.0V ≤ (V - V ) ≤ 8.7V, I
= 250µA
HI
LO
CLMP
- 0.7
CURRENT-SENSE AMPLIFIER (CSA)
Differential Input Voltage
Range
V
- V
0
0.3
V
CS+
CS-
Common-Mode Range
CS+ Input Bias Current
CS- Input Bias Current
Unity-Gain Bandwidth
REF OUTPUT BUFFER
REF Output Voltage
DIM DRIVER
V
V
V
≤ 68V
0
V
V
nA
CC
CC
I
= 0.3V, V
= 0.3V, V
= 0V
= 0V
-250
+250
400
CS+
CS+
CS+
CS-
CS-
I
µA
CS-
From (CS+ to CS-) to CS
1.0
3.0
MHz
V
-100µA ≤ I ≤ +100µA
2.85
3.15
40
V
REF
L
Minimal Pulse Width
f
= 200Hz (Note 3)
20
20
67
22
76
µs
DIM
V
V
V
V
- V = 4V
5
CLMP
CLMP
CLMP
CLMP
LO
Source Current
Sink Current
mA
- V = 8V
30
10
40
LO
- V = 4V
LO
mA
- V = 8V
LO
GATE DRIVER
DRI Voltage Range
DRI UVLO Threshold
V
V
≥ 2.5V above V
DRI
5
15
V
V
DRI
CC
V
4.0
4.2
0.3
4.4
UVLO_TH
DRI UVLO Threshold
Hysteresis
V
V
UVLO_HYST
_______________________________________________________________________________________
3
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 14V, C
= 1µF, C
= 1µF, C
= 0.1µF, R = 25kΩ, T = T = -40°C to +125°C, unless otherwise noted.
CC
UVEN
REG1
REG2
CLMP
T
A
J
Typical specifications are at T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
2.8
5.0
2.5
1.4
MAX
UNITS
Z
V
V
V
V
= 7.0V, DRV sinking 250mA
4
8
OUT_L
OUT_H
DRI
DRI
DRI
DRI
Driver Output Impedance
Ω
Z
= 7.0V, DRV sourcing 250mA
Peak Sink Current
I
I
= 7.0V
= 7.0V
A
A
SK
SR
Peak Source Current
MAX816
PWM, ILIM, AND HICCUP COMPARATOR
PWM Comparator Offset
Voltage
V
- (V
-V
)
0.8
V
COMP
SNS+ SNS-
Peak Current-Limit
Comparator Trip Threshold
160
235
200
245
385
mV
Peak Current-Limit
Comparator Propagation
Delay (Excluding Blanking
Time)
50mV overdrive
40
ns
HICCUP Comparator Trip
Threshold
300
mV
SNS+ Input Bias Current
SNS- Input Bias Current
BLANKING TIME
V
V
= 0V, V
= 0V, V
= 0V
= 0V
-100
-100
-65
-65
µA
µA
SNS+
SNS+
SNS-
SNS-
Blanking Time Control Register is ‘00’
Blanking Time Control Register is ‘01’
Blanking Time Control Register is ‘10’
Blanking Time Control Register is ‘11’
150
125
100
75
Blanking Time
ns
ERROR AMPLIFIER
FB Input Bias Current
V
V
V
= 1V
-100
+100
nA
mA
mA
FB
FB
FB
EAMP Output Sink Current
EAMP Output Source Current
= 1.735V, V
= 1V
= 1V
3
2
7
7
COMP
COMP
= 0.735V, V
EAMP Input Common-Mode
Voltage
V
(Note 5)
0
1.6
2.7
V
COM
EAMP Output Clamp Voltage
Voltage Gain
1.3
2.0
80
V
A
R
R
= 100kΩ to AGND
dB
V
COMP
= 100kΩ to AGND, C
= 100pF
COMP
COMP
Unity-Gain Bandwidth
GBW
0.5
MHz
to AGND
OSCILLATOR, OSC SYNC, CLK, AND CLKOUT
f
125
SW_MIN
SYNC Frequency Range
kHz
kHz
f
500
106
475
2.8
SW_MAX
RTOF bit set to ‘0’, R = 100kΩ
125
500
143
525
T
RTSYNC Oscillator Frequency
RTOF bit set to ‘0’, R = 25kΩ
T
SYNC High-Level Voltage
SYNC Low-Level Voltage
V
V
V
SIHL
V
0.4
SILL
4
_______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 14V, C
= 1µF, C
= 1µF, C
= 0.1µF, R = 25kΩ, T = T = -40°C to +125°C, unless otherwise noted.
CC
UVEN
REG1
REG2
CLMP
T
A
J
Typical specifications are at T = +25°C.)
A
PARAMETER
CLKOUT High Level
CLKOUT Low Level
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
I
I
= 0.8mA
2.8
V
V
SINK
= 1.6mA
0.4
SOURCE
CLKOUT Maximum Load
Capacitance
C
f
= 500kHz
500
pF
CLK_CAP
SW
DIM SYNC, DIM RAMP, AND DIM PWM GEN
Internal RAMP Frequency
f
160
80
200
240
Hz
Hz
RAMP
External Sync Frequency
Range
f
2000
DIM
External Sync Low-Level
Voltage
V
0.4
V
LTH
HTH
External Sync High-Level
Voltage
V
3.2
V
DIM Comparator Offset
V
170
200
300
mV
DIMOS
DIGITAL SOFT-START AND BINNING
Digital Soft-Start Duration register is ‘000’
Digital Soft-Start Duration register is ‘001’
Digital Soft-Start Duration register is ‘010’
Digital Soft-Start Duration register is ‘011’
Digital Soft-Start Duration register is ‘100’
Digital Soft-Start Duration register is ‘101’
Digital Soft-Start Duration register is ‘110’
Digital Soft-Start Duration register is ‘111’
Binning Adjustment register is ‘0000’
Binning Adjustment register is ‘0001’
Binning Adjustment register is ‘0010’
Binning Adjustment register is ‘0011’
Binning Adjustment register is ‘0100’
Binning Adjustment register is ‘0101’
Binning Adjustment register is ‘0110’
Binning Adjustment register is ‘0111’
Binning Adjustment register is ‘1000’
Binning Adjustment register is ‘1001’
Binning Adjustment register is ‘1010’
4096
2048
1536
1024
Soft-Start Duration
t
µs
SS
768
512
256
0
100.00
106.67
113.33
120.00
126.67
133.33
140.00
146.67
153.33
160.00
166.67
Binning Range
mV
OVERVOLTAGE COMPARATOR, LOAD OVERCURRENT COMPARATOR
OVP Overvoltage Comparator
Threshold
V
V
rising
OV
1.20
1.235
63.5
1.27
V
OV
OVP Overvoltage Comparator
Hysteresis
V
mV
OV_HYST
_______________________________________________________________________________________
5
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 14V, C
= 1µF, C
= 1µF, C
= 0.1µF, R = 25kΩ, T = T = -40°C to +125°C, unless otherwise noted.
CC
UVEN
REG1
REG2
CLMP
T
A
J
Typical specifications are at T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SLOPE COMPENSATION
Slope Compensation register is ‘0000’,
clock generated by R
0
T
Slope Compensation register is ‘0001’,
clock generated by R
20
MAX816
T
Slope Compensation register is ‘0010’,
clock generated by R
40
T
Slope Compensation register is ‘0011’,
clock generated by R
60
T
Slope Compensation register is ‘0100’,
clock generated by R
80
T
Slope Compensation register is ‘0101’,
clock generated by R
100
120
140
160
180
200
220
240
260
280
300
T
Slope Compensation register is ‘0110’,
clock generated by R
T
Slope Compensation register is ‘0111’,
clock generated by R
T
Slope Compensation Peak-to-
Peak Voltage Per Cycle
mV/
cycle
Slope Compensation register is ‘1000’,
clock generated by R
T
Slope Compensation register is ‘1001’,
clock generated by R
T
Slope Compensation register is ‘1010’,
clock generated by R
T
Slope Compensation register is ‘1011’,
clock generated by R
T
Slope Compensation register is ‘1100’,
clock generated by R
T
Slope Compensation register is ‘1101’,
clock generated by R
T
Slope Compensation register is ‘1110’,
clock generated by R
T
Slope Compensation register is ‘1111’,
clock generated by R
T
6
_______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 14V, C
= 1µF, C
= 1µF, C
= 0.1µF, R = 25kΩ, T = T = -40°C to +125°C, unless otherwise noted.
CC
UVEN
REG1
REG2
CLMP
T
A
J
Typical specifications are at T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Slope Compensation register is ‘0000’,
external clock applied to RTSYNC
0
Slope Compensation register is ‘0001’,
external clock applied to RTSYNC
2
Slope Compensation register is ‘0010’,
external clock applied to RTSYNC
4
Slope Compensation register is ‘0011’,
external clock applied to RTSYNC
6
Slope Compensation register is ‘0100’,
external clock applied to RTSYNC
8
Slope Compensation register is ‘0101’,
external clock applied to RTSYNC
10
12
14
16
18
20
22
24
26
28
30
Slope Compensation register is ‘0110’,
external clock applied to RTSYNC
Slope Compensation register is ‘0111’,
external clock applied to RTSYNC
Slope Compensation
mV/µs
Slope Compensation register is ‘1000’,
external clock applied to RTSYNC
Slope Compensation register is ‘1001’,
external clock applied to RTSYNC
Slope Compensation register is ‘1010’,
external clock applied to RTSYNC
Slope Compensation register is ‘1011’,
external clock applied to RTSYNC
Slope Compensation register is ‘1100’,
external clock applied to RTSYNC
Slope Compensation register is ‘1101’,
external clock applied to RTSYNC
Slope Compensation register is ‘1110’,
external clock applied to RTSYNC
Slope Compensation register is ‘1111’,
external clock applied to RTSYNC
_______________________________________________________________________________________
7
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 14V, C
= 1µF, C
= 1µF, C
= 0.1µF, R = 25kΩ, T = T = -40°C to +125°C, unless otherwise noted.
CC
UVEN
REG1
REG2
CLMP
T
A
J
Typical specifications are at T = +25°C.)
A
PARAMETER
FAULT I/O
SYMBOL
CONDITIONS
MIN
-1
TYP
MAX
UNITS
FAULT Leakage Current
FAULT Input Low Current
FAULT Pulldown Current
5.5V < V
< 76V
+1
µA
µA
FAULT
V
V
= 0V
= 2V
500
1.2
FAULT
FAULT
0.7
1.8
0.4
mA
MAX816
FAULT Pulldown Input
Logic-Low
V
V
IL
FAULT Output Logic-High
FAULT Output Logic-Low
Programming Slot at Power-Up
THERMAL SHUTDOWN
Sourcing 10µA
Sinking 10µA
2.8
6.4
V
V
0.4
V
> 1.244V and V
> 5.9V (Note 4)
8.0
ms
UVEN
CC
Thermal Shutdown
Temperature
T
+165
20
oC
oC
J_SHDN
Thermal Shutdown Hysteresis
EEPROM
ΔT
J_SHDN
Data Retention
t
T
= +125°C (Note 5)
10
years
ms
DR
A
EEPROM Write Time
Endurance
t
(Note 5)
14
WRA
T
= +85°C, read and write (Note 5)
50k
cycles
A
®
ELECTRICAL CHARACTERISTICS – 1-Wire System
(C
= 1µF, C
= 1µF, T = T = -40°C to +125°C, unless otherwise noted. Typical specifications are at T = +25°C.)
REG1
REG2
A
J
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
I/O GENERAL DATA
1-Wire Time Slot Duration
Recovery Time
t
65
5
µs
µs
SLOT
t
(Note 6)
REC
I/O, 1-Wire RESET, PRESENCE DETECT CYCLE
Reset Low Time
t
480
65
640
75
µs
µs
RSTL
Presence Detect Sample Time
I/O, 1-Wire WRITE
Write-0 Low Time
t
MSP
t
60
5
µs
µs
W0L
W1L
Write-1 Low Time
t
15
I/O, 1-Wire READ
Read Low Time
t
5
10
15
µs
µs
RL
Read Sample Time
t
12
MSR
1-Wire is a registered trademark of Dallas Semiconductor Corp., a wholly owned subsidiary of Maxim Integrated Products, Inc.
8
_______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
ELECTRICAL CHARACTERISTICS
Note 1: Dropout voltage is defined as the input to output differential voltage at which the output voltage drops 100mV below its nom-
inal value measured at output.
Note 2: V
determines the voltage necessary to operate the current-sense amplifier. The DIM driver requires 2.5V for (V
CLMP_TH
CLMP
- V ) to drive a FET. V is typically one diode drop above V
. A large capacitor connected to V
slows the
CLMP
LO
HI
CLMP
response of the LED current-sense circuitry, resulting in current overshoot. To ensure proper operation, connect a 0.1µF
capacitor from CLMP to LO.
Note 3: Minimum pulse width required to guarantee proper dimming operation.
Note 4: FAULT multiplexes a programming interface and fault indication functionality. At power-up initialization, an internal timer
enables FAULT and two programming passcodes must be entered within the programming slot to enter programming
mode. If the programming passcodes are not received correctly within the programming slot, FAULT goes back towards
fault indication. Cycling power to the device is required to re-attempt entry into programming mode.
Note 5: Not production tested. Guaranteed by design.
Note 6: Recovery time is the time required for FAULT to be pulled high by the internal 10kΩ resistor.
Typical Operating Characteristics
(V
= V
= 14V, C
= 1µF, C
= 10µF, C
= 0.1µF, R = 0.1Ω, Binning adjustment register is ‘0000’, T = +25°C,
CC
UVEN
REG1
REG2
CLMP
CS
A
unless otherwise noted.)
SHUTDOWN CURRENT
vs. TEMPERATURE
OPERATING CURRENT
vs. TEMPERATURE
OUTPUT CURRENT
vs. TEMPERATURE
4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.6
26
25
24
23
22
21
20
19
18
600
550
500
450
400
350
300
250
200
R
R
= 0.2Ω
= 0.3Ω
CS
CS
DGT AND DRV
NOT SWITCHING
-60 -40 -20
0
20 40 60 80 100 120 140
-60 -40 -20
0
20 40 60 80 100 120 140
-60 -40 -20
0
20 40 60 80 100 120 140
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
9
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
Typical Operating Characteristics (continued)
(V
= V
= 14V, C
= 1µF, C
= 10µF, C
= 0.1µF, R = 0.1Ω, Binning adjustment register is ‘0000’, T = +25°C,
CC
UVEN
REG1
REG2
CLMP
CS
A
unless otherwise noted.)
OUTPUT CURRENT
vs. SUPPLY VOLTAGE
OUTPUT CURRENT
vs. BINNING CODES
OUTPUT CURRENT
vs. BINNING CODES
350
300
250
200
150
100
50
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
900
800
700
600
500
400
300
200
100
0
MAX816
R
= 0.2Ω
CS
0
0
0
0
8
16 24 32 40 48 56 64 72 80
(V)
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
V
BIN (DIGITAL CODE)
BIN (DIGITAL CODE)
CC
REG2 OUTPUT VOLTAGE
vs. TEMPERATURE
REG2 OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
REG2 OUTPUT VOLTAGE
vs. REG2 CONTROL REGISTER
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
18
16
14
12
10
8
16
15
14
13
12
11
10
9
REG2 CONTROL REGISTER = '1111', V = 20V
CC
REG2 CONTROL REGISTER = '1111', V = 20V
CC
REG2 CONTROL REGISTER = '0000'
6
8
7
4
REG2 CONTROL REGISTER = '0000'
6
2
5
I
= 20mA
I
= 20mA
I
= 20mA
REG2
REG2
REG2
0
0
4
-60 -40 -20
0
20 40 60 80 100 120 140
8
16 24 32 40 48 56 64 72 80
(V)
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
TEMPERATURE (°C)
V
DRPS (DIGITAL CODE)
CC
REG1 OUTPUT VOLTAGE
vs. TEMPERATURE
REG1 OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
CLMP OUTPUT VOLTAGE
vs. TEMPERATURE
6
5
4
3
2
1
5.4
5.3
5.2
5.1
5.0
4.9
4.8
4.7
4.6
8.3
8.2
8.1
8.0
7.9
7.8
7.7
7.6
7.5
V
- V = 9V
LO
HI
I
= 2mA
REG1
I
= 2mA
CLMP VOLTAGE = V
- V
REG1
CLMP LO
0
0
10 20 30 40 50 60 70 80
(V)
-60 -40 -20
0
20 40 60 80 100 120 140
-60 -40 -20
0
20 40 60 80 100 120 140
V
TEMPERATURE (°C)
TEMPERATURE (°C)
CC
10 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
Typical Operating Characteristics (continued)
(V
= V
= 14V, C
= 1µF, C
= 10µF, C
= 0.1µF, R = 0.1Ω, Binning adjustment register is ‘0000’, T = +25°C,
CC
UVEN
REG1
REG2
CLMP
CS
A
unless otherwise noted.)
REF VOLTAGE
vs. TEMPERATURE
REF VOLTAGE
vs. SINK CURRENT
PWM OSCILLATION FREQUENCY
vs. TEMPERATURE
3.025
3.020
3.015
3.010
3.005
3.000
3.12
3.10
3.08
3.06
3.04
3.02
3.00
2.98
2.96
135
134
133
132
131
130
129
128
127
126
125
124
123
122
121
120
I
= 100μA
R = 100kΩ
T
REF
-225 -175 -125 -75 -25 25 75 125 175 225
(μA)
-60 -35 -10 15 40 65 90 115 140
-60 -35 -10 15 40 65 90 115 140
I
TEMPERATURE (°C)
TEMPERATURE (°C)
REF
RT RESISTANCE
vs. PWM FREQUENCY
LED CURRENT DUTY CYCLE
vs. DIM VOLTAGE
200Hz DIMMING OPERATION
MAX16816 toc17
550
500
450
400
350
300
250
200
150
100
100
90
80
70
60
50
40
30
20
10
0
10%
DIMMING
1A/div
0A
0A
50%
DIMMING
1A/div
90%
DIMMING
1A/div
0A
0.005
0.015
0.025
0.035
-1
0.045
0
1
2
3
2ms/div
1/RT RESISTANCE (kΩ
)
DIM VOLTAGE (V)
DRIVER DRV RISE TIME
vs. DRI VOLTAGE
DRIVER DRI FALL TIME
vs. DRI VOLTAGE
45
40
35
30
25
20
15
10
5
70
60
50
40
30
20
10
0
5nF CAPACITOR CONNECTED
FROM DRV TO AGND
5nF CAPACITOR CONNECTED
FROM DRV TO AGND
0
5
7
9
11 13
15
5
7
9
11
13
15
DRI VOLTAGE (V)
DRI VOLTAGE (V)
______________________________________________________________________________________ 11
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
Pin Description
PIN
NAME
FUNCTION
1, 24
N.C.
No Connection. Not internally connected.
Undervoltage Lockout (UVLO) Threshold/Enable Input. UVEN is a dual-function adjustable UVLO threshold
input with an enable feature. Connect UVEN to V through a resistive voltage-divider to program the UVLO
threshold. Connect UVEN directly to V to use the 5.9V (max) default UVLO threshold. Apply a voltage
CC
greater than 1.244V to UVEN to enable the device.
CC
2
3
UVEN
REG1
5V Regulator Output. REG1 is an internal low-dropout voltage regulator that generates a 5V (V
> 6V)
CC
MAX816
output voltage and supplies power to internal circuitry. Bypass REG1 to AGND through a 1µF ceramic
capacitor.
Analog Ground. Use proper single-point ground design and decoupling to avoid ground impedance loop
errors.
4
5
AGND
REF
Accurate 3V Buffered Reference Output. Connect REF to DIM through a resistive voltage-divider to apply a
DC voltage for analog-controlled dimming functionality. Leave REF unconnected if unused.
Dimming Control Input. Connect DIM to an external PWM signal for PWM dimming. For analog-controlled
dimming, connect DIM to REF through a resistive voltage-divider. The dimming frequency is 200Hz under
these conditions. Connect DIM to AGND to turn off the LEDs.
6
7
DIM
Sync Input/Output. The internal PWM clock is selectable through the RTOF EEPROM bit. Connect an
external resistor to RTSYNC and set the RTOF register to ‘0’ to select a clock frequency between 125kHz
RTSYNC and 500kHz. Set RTOF register to ‘0’ and connect RTSYNC to an external clock to synchronize the device
with external clock. Set RTOF register to ‘1’ to use the fixed 125kHz oscillator. Under these conditions,
RTSYNC is powered off and may be left in any state. See the Oscillator, Clock, and Synchronization section.
Clock Output. CLKOUT buffers the oscillator/clock. Connect CLKOUT to the SYNC input of another device
CLKOUT
8
9, 10, 11
12
to operate the MAX16816 in a multichannel configuration. CLKOUT is a logic output.
I.C.
Internally Connected. Must be connected to AGND.
Error-Amplifier Output. Connect the compensation network from COMP to FB for stable closed-loop control.
Use low-leakage ceramic capacitors in the feedback network.
COMP
Current-Sense Voltage Output. CS outputs a voltage proportional to the current sensed through the current-
sense amplifier. Connect CS through a passive network to FB as dictated by the chosen compensation
scheme.
13
14
CS
FB
Error-Amplifier Inverting Input
Overvoltage Protection Input. Connect OV to HI through a resistive voltage-divider to set the overvoltage
limit for the load. When the voltage at OV exceeds the 1.235V (typ) threshold, an overvoltage fault is
generated and the switching MOSFET turns off. The MOSFET is turned on again when the voltage at OV
drops below 1.17V (typ).
15
OV
16, 17
18
SGND
DRV
Switching Ground. SGND is the ground for non-analog and high-current gate-driver circuitry.
Gate-Driver Output. Connect DRV through a series resistor to the gate of an external n-channel MOSFET to
reduce EMI. DRV can sink 1A or source 0.5A.
19
DRI
Gate-Driver Supply Input. Connect DRI to REG2 to power the primary switching MOSFET driver.
Positive Peak Current-Sense Input. Connect SNS+ to the positive side of the switch current-sense resistor,
20
SNS+
R
.
SENSE
12 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
Pin Description (continued)
PIN
21
NAME
SNS-
FUNCTION
Negative Peak Current-Sense Input. Connect SNS- to the negative side of the switch current-sense resistor,
R
.
SENSE
22
QGND
DGT
Analog Ground. Ensure a low-impedance connection between QGND and AGND.
Dimming Gate-Driver Output. Connect DGT to the gate of an external n-channel MOSFET for dimming. DGT
is powered by the internal regulator, CLAMP, and is referenced to LO.
23
Low-Voltage Input. LO is the return point for the LED current. When using the MAX16816 in a buck-boost
configuration, connect LO to V . When using the device in a boost configuration only, connect LO to
AGND. Connect LO to the junction of the inductor and LED current-sense resistor, R , when using a buck
CS
CC
25
LO
configuration.
Noninverting Current-Sense Amplifier Input. Connect CS+ to the positive side of an external sense resistor,
26
27
CS+
CS-
R , connected in series with the load (LEDs).
CS
Inverting Current-Sense Amplifier Input. Connect CS- to the negative side of an external sense resistor, R
connected in series with the load (LEDs).
,
CS
Internal CLAMP Regulator Bypass. CLAMP supplies an 8V (typ) output when V ≥ 9V. If V is lower than
HI
HI
9V, V
is one diode drop below V . The CLAMP regulator powers the current-sense amplifier and
CLMP
HI
28
29
CLMP
provides the high reference for the dimming driver. V
the current-sense amplifier and dimming MOSFET driver. Bypass CLMP to LO with a 0.1µF ceramic
capacitor.
must be at least 2.5V higher than V to enable
CLMP LO
High-Voltage Input. HI is referred to LO. HI supplies power to the current-sense amplifier and dimming
MOSFET gate driver through the CLMP regulator.
HI
Internal Regulator Output. REG2 is an internal voltage regulator that generates EEPROM-programmable
(5V to 15V) output and supplies power to internal circuitry. Connect REG2 to DRI to power the switching
MOSFET driver during normal operation. Bypass REG2 to AGND with a 10µF ceramic capacitor.
30
31
32
REG2
V
Supply Voltage Input
CC
FAULT Input/Output. FAULT is a bidirectional high-voltage logic input/output. FAULT multiplexes a 1-Wire
programming interface with a fault indicator. FAULT is internally pulled up to 5V through a 10kΩ resistor and
FAULT
a 1.8mA (max) current pulldown to ground.
Exposed Pad. Connect EP to AGND. EP also functions as a heatsink to maximize thermal dissipation. Do not
use as the main ground connection.
EP
EP
______________________________________________________________________________________ 13
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
Functional Diagram
CLMP
LO
V
CC
HI
CS- CS+
-
CSA
UVLO
AND
EN
5V
REG1
15V
REG2
CLAMP
V
LO
V
CLMP
MAX816
UVEN
REG2
DGT
D-I
REG2 DRIVER
THERMAL
SHUTDOWN
R
LS
V
CLMP
QGND
REG1
UGB
SLOPE
SLOPE
COMP
DDR
V
D-I
-
V
REF
BUF
+
LO
3.0V
+
CS
CMP
-
1.3 x V
SS
1-Wire
INTERFACE
FAULT
RTSYNC
CLKOUT
OSC
OSC
OC
DRI
POR
EN
CONTROL
BLOCK
V
DRIVER
OV
DRV
-
OV
OVP
SGND
SNS+
+
OV
+
ILIM
-
-
+
200mV
300mV
DIM
SNS-
COMP
-
+
-
+
-
200mV
HIC
AGND
-
D-I BLANKING
BLANKING
TIME
MAX16816
200Hz
PWM
SLOPE
800mV
-
+
-
SS
0.926V
OS
V
SS
X1
+
COMP
FB
EAMP
TRIM REGISTERS
D-I
BLANKING
D-I
SLOPE COMP
SOFT-START
RTOSCSEL
D-I
BINNING
REG2 DRIVER
SOFT-START
BINNING
D-I
INDICATES A USER-PROGRAMMABLE EEPROM FEATURE
14 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
ered to the load during severe fault conditions. A non-
Detailed Description
latching overvoltage protection limits the voltage on the
The MAX16816 is a current-mode PWM LED driver for
external switching MOSFET (Q ) under open-circuit
S
use in driving HB LEDs. An output current accuracy of
5% is achievable using two current regulation loops:
one current regulation loop controls the external switch-
ing MOSFET peak current through a sense resistor,
conditions in the LED string. During continuous opera-
tion at high input voltages, the power dissipation of the
MAX16816 could exceed the maximum rating and the
internal thermal shutdown circuitry safely turns off the
MAX16816 when the device junction temperature
exceeds +165°C. When the junction temperature drops
below the hysteresis temperature, the MAX16816 auto-
matically reinitiates startup.
R
, from SNS+ to SNS- while the other current reg-
SENSE
ulation loop controls the average LED string current
through the sense resistor, R , in series with the
CS
LEDs. The wide operating supply range of 5.9V/5.4V
(ON/OFF) to 76V makes the MAX16816 ideal in auto-
motive applications.
Undervoltage Lockout/Enable (UVEN)
The MAX16816 features a dual-purpose adjustable
undervoltage lockout input and enable function
The MAX16816 provides LED binning through one pro-
grammable on-chip nonvolatile EEPROM. The LED cur-
rent can be scaled up to a factor of 1.6. This feature is
used to offset factory LED luminance variations and
allows the system to achieve overall luminance accuracy.
(UVEN). Connect UVEN to V
through a resistive volt-
CC
age-divider to set the undervoltage lockout (UVLO)
threshold. The device is enabled when the voltage at
UVEN exceeds the 1.244V (typ) threshold. Drive UVEN
to ground to disable the output.
A programmable undervoltage lockout (UVEN) ensures
predictable operation during brownout conditions. The
UVEN input circuitry monitors the supply voltage, V
,
CC
Setting the UVLO Threshold
and turns the driver off when V
drops below the
CC
Connect UVEN directly to V
to select the default 5.7V
CC
UVLO threshold. Connect UVEN to V
to use the 5.7V
CC
(typ) UVLO threshold. Connect UVEN to V
through a
CC
(typ) default UVLO threshold. The MAX16816 includes
a cycle-by-cycle current limit that turns off the gate
drive to the external switching MOSFET (Q ) during an
S
overcurrent condition and a programmable oscillator
that simplifies and optimizes the design of external
magnetics.
resistive voltage-divider to select a UVLO threshold
(Figure 1). Select the desired UVLO threshold voltage,
V
, and calculate resistor values using the following
UVLO
equation:
⎛
⎞
V
UVEN
- V
UVEN
R
= R
x
UV1
UV2
UV2
⎜
⎟
V
The MAX16816 is capable of synchronizing to an
external clock or operating in a stand-alone mode. A
single resistor, R , can be used to adjust the switching
T
frequency from 125kHz to 500kHz for stand-alone
operation. To synchronize the device with an external
clock, apply a clock signal directly to the RTSYNC
input. A buffered clock output, CLKOUT, is available to
configure the MAX16816 for multichannel applications.
The external RT oscillator can be disabled by setting
EEPROM register RTOF to ‘1’.
⎝
⎠
UVLO
where R
+ R
≤ 270kΩ. V
UVEN threshold voltage.
is the 1.244V (typ)
UVEN
UV1
V
IN
R
R
The MAX16816 provides wide contrast pulsed dimming
(up to 1000:1) utilizing a separate dimming input. Apply
either a DC level voltage or low-frequency PWM signal
to the dimming input. DC level input results in a 200Hz
fixed dimming frequency.
UV2
V
CC
UVEN
MAX16816
QGND
C
UVEN
UV1
The MAX16816 provides configurable on-chip non-
volatile EEPROM features including a programmable
soft-start, load current, external MOSFET gate-driver
supply voltage, blanking time, and slope compensation.
Protection features include peak current limiting, HICCUP
mode current limiting, output overvoltage protection,
short-circuit protection, and thermal shutdown. The
HICCUP current-limit circuitry reduces the power deliv-
Figure 1. Setting the UVLO Threshold
______________________________________________________________________________________ 15
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
The capacitor C
is required to prevent chattering
Reference Voltage Output (REF)
The MAX16816 includes a 5% accurate, 3V (typ)
buffered reference output, REF. REF is a push-pull out-
put capable of sourcing/sinking up to 200µA of current
and can drive a maximum load capacitance of 100pF.
Connect REF to DIM through a resistive voltage-divider
to supply an analog signal for dimming. See the
Dimming Input (DIM) section for more information.
UVEN
at the UVLO threshold due to line impedance drops
during power-up and dimming. If the undervoltage set-
ting is very close to the required minimum operating
voltage, there can be large jumps in the voltage at V
CC
during dimming, which may cause the MAX16816 to
turn on and off when the dimming signal transitions
from low to high. The capacitor C
should be large
UVEN
enough to limit the ripple on UVEN to less than the
100mV (min) UVEN hysteresis so that the device does
not turn off under these circumstances.
Dimming MOSFET Driver (DDR)
The MAX16816 requires an external n-channel MOSFET
for PWM dimming. Connect the MOSFET to the output of
the DDR dimming driver, DGT, for normal operation.
MAX816
Soft-Start
The MAX16816 features a digitally programmable soft-
start delay that allows the load current to ramp up in a
controlled manner, minimizing output overshoot. Soft-
V
swings between V
and V
. The DDR dim-
CLMP
DGT
LO
ming driver is capable of sinking or sourcing up to
20mA of current. The average current required to drive
start begins once the device is enabled and V
CC
the dimming MOSFET (I
) depends on the
G_DIM
Use the following equa-
DRIVE_DIM
MOSFET’s total gate charge (Q
exceeds the UVLO threshold. Soft-start circuitry slowly
) and the dimming
increases the internal soft-start voltage, V , resulting
SS
frequency of the converter, f
DIM.
in a controlled rise of the load current. Signals applied
to DIM are ignored until the soft-start duration is com-
plete and a successive delay of 200µs has elapsed.
Use the Digital Soft-Start Duration register in the EEPROM
to select a soft-start duration from 0 (no delay) to
4.096ms. See the EEPROM and Programming section for
more information on using the Digital Soft-Start Duration
register.
tion to calculate the supply current for the n-channel dim-
ming FET driver.
I
= Q
x f
DRIVE_DIM
G_DIM DIM
n-Channel MOSFET Switch Driver (DRV)
The MAX16816 drives an external n-channel MOSFET
for switching. Use an external supply or connect REG2
to DRI to power the MOSFET driver. The driver output,
V
V
, swings between ground and V . Ensure that
DRI
DRV
DRI
Regulators (REG1, REG2, CLAMP)
The MAX16816 includes a fixed 5V voltage regulator,
REG1; an EEPROM-adjustable regulator, REG2; and an
internal 8V regulator, CLAMP. REG1 and REG2 power
remains below the absolute maximum V
rating
GS
of the external MOSFET. DRV is capable of sinking 2A
or sourcing 1.4A of peak current, allowing the
MAX16816 to switch MOSFETs in high-power applica-
tions. The average current sourced to drive the external
up when V
exceeds the UVLO threshold. REG1 sup-
CC
plies power to internal circuitry and remains on during
PWM dimming. REG1 is capable of driving external
loads up to 2mA.
MOSFET depends on the total gate charge (Q ) and
G
operating frequency of the converter, f . The power
SW
dissipation in the MAX16816 is a function of the aver-
Use the REG2 Control Register in the EEPROM to
select an output voltage from 5V to 15V for REG2.
Connect REG2 to DRI to generate the supply voltage
for the primary switching MOSFET driver, DRV. REG2 is
capable of delivering up to 20mA of current. See the
EEPROM and Programming section for more information
on configuring the REG2 output voltage.
age output drive current (I
). Use the following
DRIVE
equations to calculate the power dissipation in the
gate-driver section of the MAX16816 due to I
:
DRIVE
I
= Q x f
G SW
DRIVE
P = I
x V
DRI
D
DRIVE
where V
is the supply voltage to the gate driver.
DRI
CLAMP is powered by HI and supplies power to the
current-sense amplifier (CSA). CSA is enabled when
Dimming Input (DIM)
The dimming input, DIM, functions with either analog or
PWM control signals. Once the internal pulse detector
detects three successive edges of a PWM signal with a
frequency between 80Hz and 2kHz, the MAX16816
synchronizes to the external signal and pulse-width
modulates the LED current at the external DIM input
frequency with the same duty cycle as the DIM input. If
V
goes 2.5V above V
and is disabled when
LO
CLMP
(V
V
) falls below 2.28V. The CLAMP regulator
CLMP - LO
also provides power to the dimming MOSFET control
circuitry. CLMP is the output of the CLAMP regulator.
Do not use CLMP to power external circuitry. Bypass
CLMP to LO with a 0.1µF ceramic capacitor. A larger
capacitor will result in overshoot of the load current.
16 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
an analog control signal is applied to DIM, the
MAX16816 compares the DC input to an internally gen-
erated 200Hz ramp to pulse-width modulate the LED
To synchronize the MAX16816 with an external clock
signal ranging from 125kHz to 500kHz, set the RTOF bit
to ‘0’ and connect the clock signal to the RTSYNC
input. The MAX16816 synchronizes to the clock signal
after the detection of 5 successive clock edges at
RTSYNC.
current (f
= 200Hz). The output current duty cycle is
DIM
linearly adjustable from 0 to 100% (0.2V < V
< 2.8V).
DIM
Use the following formula to calculate voltage, V
necessary for a given output current duty cycle, D:
,
DIM
A buffered clock output, CLKOUT, can drive the
RTSYNC input of an external PWM controller for multi-
channel applications. CLKOUT can drive capacitive
loads up to 500pF.
V
DIM
= (D x 2.6) + 0.2V
where V
is the voltage applied to DIM in volts.
DIM
Connect DIM to REF through a resistive voltage-divider
to apply a DC DIM control signal (Figure 2). Use the
If the PWM switching frequency is set to 125kHz, the
RTSYNC oscillator can be temporarily disabled by setting
the EEPROM RTOF bit to ‘1’. In this case, the internal
125kHz frequency-fixed oscillator drives the PWM. See the
EEPROM and Programming section for more information
on setting the Oscillator Enable/Disable bit in the EEPROM.
required dimming input voltage, V
, calculated
DIM
above and select appropriate resistor values using the
following equation:
R = R x V
/ (V
- V
)
DIM
4
3
DIM
REF
where V
is the 3V reference output voltage and
4
REF
Multichannel Configuration
The MAX16816 is capable of multichannel operation
and is configurable as a master or slave in a Master-
Slave configuration, or in a Peer-to-Peer configuration.
Connect CLKOUT to the SYNC input of an external
device to use the MAX16816 as a master clock signal.
Connect an external clock signal to RTSYNC to config-
ure the MAX16816 as a slave. To setup two MAX16816
devices in a daisy-chain configuration, drive the
RTSYNC input of one MAX16816 with the CLKOUT
buffer of another (Figure 3).
15kΩ ≤ R + R ≤ 150kΩ.
3
A minimum 20µs pulse width is necessary for proper
operation during dimming.
Oscillator, Clock, and Synchronization
The MAX16816 is capable of stand-alone operation, of
synchronizing to an external clock, and of driving exter-
nal devices in SYNC mode. For stand-alone operation,
set the EEPROM Oscillator Enable/Disable (RTOF) bit
to ‘1’ to use the fixed internal 125kHz oscillator or set
RTOF to ‘0’ and program the switching frequency by
connecting a single external resistor, R , between
T
RTSYNC and ground. Select a switching frequency,
ILIM and HICCUP Comparator
R
sets the peak current through the inductor for
SENSE
f
, between 125kHz and 500kHz and calculate R
T
switching. The differential voltage across R
is
SW
SENSE
using the following formula:
compared to the 200mV voltage-trip limit of the current-
limit comparator, ILIM. Set the current limit 20% higher
than the peak switch current at the rated output power
and minimum voltage. Use the following equation to
500kHz
R
=
× 25kΩ
T
f
SW
calculate R
:
SENSE
where the switching frequency is in kHz and R is in kΩ.
R
= V
/ (1.2 x I
)
PEAK
T
SENSE
SENSE
REF
SLAVE/PEER
MAX16816
MASTER/PEER
MAX16816
R
R
3
MAX16816
AGND
DIM
RTSYNC
CLKOUT
RTSYNC
CLKOUT
4
R
T
Figure 2. Creating DIM Input Signal from REF
Figure 3. Master-Slave/Peer-Peer Clock Configuration
______________________________________________________________________________________ 17
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
where V
is the 200mV maximum differential volt-
See the EEPROM and Programming section for more infor-
mation on the ESLP register.
SENSE
age between SNS+ and SNS- and I
is the peak
PEAK
inductor current at full load and minimum input voltage.
Internal Voltage-Error Amplifier (EAMP)
The MAX16816 includes a built-in voltage amplifier,
with three-state output, which can be used to close the
feedback loop. The buffered output current-sense sig-
nal appears at CS, which is connected to the inverting
input, FB, of the error amplifier through resistor R . The
1
noninverting input is connected to an internally trimmed
current reference.
When the voltage drop across R exceeds the
SENSE
ILIM threshold, the MOSFET driver (DRV) terminates
the on-cycle and turns the switch off, reducing the cur-
rent through the inductor. The FET is turned back on at
the beginning of the next switching cycle.
When the voltage across R
exceeds the 300mV
SENSE
(typ) HICCUP threshold, the HIC comparator terminates
the on-cycle of the device, turning the switching MOS-
FET off. Following a startup delay of 8ms (typ), the
MAX16816 reinitiates soft-start. The device will continue
to operate in HICCUP mode until the overcurrent condi-
tion is removed.
MAX816
The output of the error amplifier is controlled by the signal
applied to DIM. When DIM is high, the output of the ampli-
fier is connected to COMP. The amplifier output is open
when DIM is low. This enables the integrating capacitor to
hold the charge when the DIM signal has turned off the
gate drive. When DIM is high again, the voltage on the
A programmable built-in leading-edge blanking circuit
of the current-sense signal prevents these comparators
from prematurely terminating the on-cycle of the exter-
compensation capacitors, C and C , forces the converter
1
2
into steady state almost instantaneously.
nal switching MOSFET (Q ). Select a blanking time
S
PWM Dimming
from 75ns to 150ns by configuring the Blanking Time
register in the EEPROM. In some cases, the maximum
blanking time may not be adequate and an additional
RC filter may be required to prevent spurious turn-off.
PWM dimming is achieved by driving DIM with either a
PWM signal or a DC signal. The PWM signal is con-
nected internally to the error amplifier, the dimming
MOSFET gate driver, and the switching MOSFET gate
driver. When the DIM signal is high, the dimming MOSFET
and the switching MOSFET drivers are enabled and the
output of the voltage-error amplifier is connected to
the external compensation network. Also, the buffered
current-sense signal is connected to CS. Preventing
discharge of the compensation capacitor when the
DIM signal is low allows the control loop to return the
LED current to its original value almost instantaneously.
Load Current Sense
The load sense resistor, R , monitors the current
CS
through the LEDs. The internal floating current-sense
amplifier, CSA, measures the differential voltage across
R
, and generates a voltage proportional to the load
CS
current through R
at CS. This voltage on CS is
CS
referred to AGND. The closed-loop regulates the load
current to a value, I
, given by the following equation:
LED
I
= V / R
When the DIM signal goes low, the output of the error
amplifier is disconnected from the compensation net-
LED
SS
CS
where V is the binning adjustment voltage. Set the value
of V in the Binning Adjustment register in the EEPROM
between 100mV and 166mV. See the EEPROM and
Programming section for more information on adjusting
the binning voltage.
SS
work and the compensation capacitors, C and C ,
1
2
SS
voltage is preserved. Choose low-leakage capacitors
for C and C . The drivers for the external dimming and
1
2
switching MOSFETs are disabled, and the converter
stops switching. The inductor energy is now transferred
to the output capacitors.
Slope Compensation
The amount of slope compensation required is largely
dependent on the down-slope of the inductor current
When the DIM signal goes high and the gate drivers
are enabled, the additional voltage on the output
capacitor may cause a current spike on the LED string.
A larger output capacitor will result in a smaller current
spike. If the overcurrent spike exceeds 30% of the pro-
grammed LED current, the dimming is turned off and
the MAX16816 reinitiates soft-start.
when the switching MOSFET, Q , is off. The inductor
S
down-slope depends on the input-to-output voltage dif-
ferential of the converter, the inductor value, and the
switching frequency. For stability, the compensation
slope should be equal to or greater than half of the
inductor current down-slope multiplied by the current-
sense resistance (R
).
SENSE
18 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
device. Under these conditions, FAULT will go low only
when a fault (overvoltage, overcurrent, or HICCUP mode)
occurs or when the supply voltage drops below the UVLO
threshold.
FAULT 1-Wire Interface
The MAX16816 features a FAULT output multiplexed
with a 1-Wire programming interface. Once the voltage
at UVEN exceeds the UVLO threshold, the device is
enabled and FAULT will pulse low once, indicating the
beginning of the programming window. Two program-
ming mode entry codes must be entered within 8ms
after the pulse to enter programming mode (see Table
1). The MAX16816 will register the second entry code
only after the first code has been received. Once the
MAX16816 successfully enters programming mode, the
data and clock for the 1-Wire interface are supplied
through FAULT.
EEPROM and Programming
Nonvolatile EEPROM is available to configure the
MAX16816 through a 1-Wire serial interface. Registers
are located in a linear address space as shown in
Table 2. All other EEPROM locations are reserved.
Configure the six control registers to adjust parameters
including the REG2 voltage, soft-start durations, blank-
ing time, LED load current (binning), slope compensa-
tion, and to enable/disable the RTOF oscillator. See the
1-Wire Interface section for more information about
1-Wire programming.
Once the programming window has passed, the EEPROM
is no longer accessible without cycling power to the
Table 1. Programming Mode Entry Codes
PROGRAMMING MODE
HEX
CODE
D7
D6
D5
D4
D3
D2
D1
D0
ENTRY CODE
PASS_CODE_1
PASS_CODE_2
0
0
0
0
1
0
0
0
1
1
0
0
0
0
1
1
29h
09h
Table 2. EEPROM Memory Map
EEPROM
ADDRESS
RANGE
NO. OF
BITS
REGISTER
TYPE
DESCRIPTION
Binning Adjustment (BIN)
REG2 Control (DRPS)
24h–27h
28h–2Bh
32h–33h
4
4
2
R/W
R/W
R/W
Adjusts the LED current.
Sets the output voltage for REG2. Connect REG2 to DRI
to supply the high-side voltage for the gate driver, DRV.
Blanking Time Adjustment (BLNK)
Adjusts the blanking time for debouncing.
Adjusts the soft-start duration to allow the load current to
ramp up in a controlled manner, minimizing output
overshoot.
Digital Soft-Start Duration (SS)
34h–36h
2
R/W
Internal Oscillator
Enable/Disable (RTOF)
Enables/disables the internal oscillator for stand-alone
operation or to synchronize with an external clock.
37h
1
4
R/W
R/W
Slope Compensation (ESLP)
38h–3Bh
Adjusts the slope compensation for stability.
______________________________________________________________________________________ 19
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
Binning Adjustment Register (BIN)
The MAX16816 uses a feedback loop to control the
load current. The differential voltage across the current-
Adjust REG2 by programming the REG2 Control
Register. See Table 4.
Blanking Time Adjustment Register (BLNK)
sense resistor, R , is compared with an internal
CS
The MAX16816 features a programmable blanking time
to mask out the current-sense signal for a short dura-
tion to avoid the ILIM and HICCUP comparators from
prematurely terminating the on-cycle of the switching
MOSFET. This blanking time allows for higher input cur-
rent during startup without triggering a fault condition.
The blanking time is adjustable in the range of 150ns to
75ns by configuring the EEPROM. See Table 5.
adjustable reference to regulate the LED current. The
voltage across the sense resistor is measured differen-
tially to achieve high immunity to common-mode noise.
The MAX16816 includes a factory-set regulation volt-
age of 133mV 3% across R . Adjust the differential
CS
regulation voltage by programming the binning adjust-
ment register (see Table 3). The reference voltage level
may not necessarily be equal to the regulation voltage.
There are offsets involved that are trimmed at the facto-
ry. Read the default register code and step up the code
by one to increase the regulation voltage by 6.66mV.
Step down the code by one to reduce the regulation
voltage by 6.66mV.
MAX816
Table 4. REG2 Control Register
REG2 OUTPUT
VOLTAGE
(V)
EEPROM ADDRESS
2Bh
2Ah
29h
28h
REG2 Control Register (DRPS)
REG2 is EEPROM configurable to supply a voltage rang-
ing from 5V to 15V and is capable of sourcing up to
20mA. Connect REG2 to the primary switching MOSFET
gate-driver supply input, DRI, for normal operation.
5.000
5.667
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
6.333
7.000*
7.667
8.333
Table 3. Binning Adjustment Register
9.000
REFERENCE
VOLTAGE LEVEL
(mV)
EEPROM ADDRESS
9.667
10.333
11.000
11.667
12.333
13.000
13.667
14.333
15.000
27h
26h
25h
24h
100.00
106.67
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
113.33
120.00
126.67
133.33
140.00
*Factory default
146.67
153.33
Table 5. Blanking Time
160.00
166.67
EEPROM ADDRESS
BLANKING TIME
173.33*
180.00*
186.67*
193.33*
200.00*
*Not recommended
(ns)
33h 32h
150*
125
0
0
0
1
1
1
0
1
100
75
*Factory default
20 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
Digital Soft-Start Duration Register (SS)
Table 8. Slope Compensation with Clock
Generated by RT Oscillator
The MAX16816 programmable soft-start feature allows
the load current to ramp up in a controlled manner, elimi-
nating output overshoot during startup. Soft-start begins
SLOPE
EEPROM ADDRESS
COMPENSATION
(mV/clock cycle)
once the device is enabled and V
has exceeded the
CC
3Bh
3Ah
39h
38h
5.5V (min) rising threshold voltage. Adjust the soft-start
duration by configuring the EEPROM. Enter ‘111’ to dis-
able the soft-start feature. See Table 6.
0
20
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
40
Oscillator Enable/Disable Register (RTOF)
The MAX16816 features a programmable accurate
RTSYNC oscillator and resistor synchronized to an
external clock. Set the EEPROM bit RTOF to ‘1’ to dis-
able the external sync mode, and the RTSYNC oscilla-
tor, and to use the fixed internal frequency of 125kHz
as the switching frequency. Set RTOF to ‘0’ to synchro-
nize with an external oscillator or to program the exter-
60
80
100
120*
140
160
180
200
nal oscillator frequency with an external resistor, R .
T
See Table 7.
220
Slope Compensation Register (ESLP)
The MAX16816 uses an internally generated ramp to
stabilize the current loop when operating at duty cycles
above 50%. Set the compensating slope by adjusting
the peak ramp voltage through the on-chip EEPROM.
See Tables 8 and 9.
240
260
280
300
*Factory default
Table 9. Slope Compensation with
External Clock Applied to RTSYNC or RT
Oscillator Off
Table 6. Digital Soft-Start Duration
EEPROM ADDRESS
DURATION
(µs)
SLOPE
COMPENSATION
EEPROM ADDRESS
36h
0
35h
0
34h
0
4096*
3Bh
3Ah
39h
38h
(mV/µs)
2048
0
0
1
0
2
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1860
0
1
0
1024
0
1
1
4
768
512
1
0
0
6
8
1
0
1
10
12*
14
16
18
20
22
24
26
28
30
256
1
1
0
No SS
1
1
1
*Factory default
Table 7. Oscillator Enable/Disable
EEPROM ADDRESS
RT OSCILLATOR
37h
1
RT Oscillator Off
RT Oscillator On*
0
*Factory default
*Factory default
______________________________________________________________________________________ 21
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
Fault Protection
Applications Information
The MAX16816 features built-in overvoltage protection,
overcurrent protection, HICCUP mode current-limit pro-
tection, and thermal shutdown. Overvoltage protection
is achieved by connecting OV to HI through a resistive
voltage-divider. HICCUP mode limits the power dissi-
pation in the external MOSFETs during severe fault
conditions. Internal thermal shutdown protection safely
turns off the converter when the IC junction temperature
exceeds +165°C.
Inductor Selection
The minimum required inductance is a function of oper-
ating frequency, input-to-output voltage differential, and
the peak-to-peak inductor current (ΔI ). Higher ΔI
L
L
allows for a lower inductor value while a lower ΔI
L
requires a higher inductor value. A lower inductor value
minimizes size and cost, improves large-signal tran-
sient response, but reduces efficiency due to higher
peak currents and higher peak-to-peak output ripple
voltage for the same output capacitor. On the other
hand, higher inductance increases efficiency by reduc-
MAX816
Overvoltage Protection
The overvoltage protection (OVP) comparator com-
pares the voltage at OV with a 1.235V (typ) internal ref-
erence. When the voltage at OV exceeds the internal
reference, the OVP comparator terminates PWM
switching and no further energy is transferred to the
load. The MAX16816 reinitiates soft-start once the over-
voltage condition is removed. Connect OV to HI
through a resistive voltage-divider to set the overvolt-
age threshold at the output.
ing the ripple current, ΔI . However, resistive losses
L
due to extra turns can exceed the benefit gained from
lower ripple current levels, especially when the induc-
tance is increased without also allowing for larger
inductor dimensions. A good compromise is to choose
ΔI equal to 30% of the full load current. The inductor
L
saturating current is also important to avoid runaway
current during the output overload and continuous
short circuit. Select the I
mum peak current limit.
to be higher than the maxi-
SAT
Setting the Overvoltage Threshold
Connect OV to HI or to the high-side of the LEDs
through a resistive voltage-divider to set the overvolt-
age threshold at the output (Figure 4). The overvoltage
protection (OVP) comparator compares the voltage at
OV with a 1.235V (typ) internal reference. Use the fol-
lowing equation to calculate resistor values:
Buck configuration: In a buck configuration the average
inductor current does not vary with the input. The worst-
case peak current occurs at high input voltage. In this
case the inductance, L, for continuous conduction
mode is given by:
V
x V
− V
(
)
V
− V
OV
⎛
⎞
OUT
INMAX OUT
OV_LIM
L =
R
= R
x
OV2
OV1
⎜
⎟
V
x f
x ΔI
V
⎝
⎠
INMAX
SW L
OV
where V
is the maximum input voltage, f
is the
INMAX
SW
where V
is the 1.235V OV threshold. Choose R
OV1
OV
switching frequency, and V
is the output voltage.
OUT
and R
to be reasonably high value resistors to pre-
OV2
vent discharge of filter capacitors. This will prevent
unnecessary undervoltage and overvoltage conditions
during dimming.
Load-Dump Protection
The MAX16816 features load-dump protection up to 76V.
LED drivers using the MAX16816 can sustain single fault
load dump events. Repeated load dump events within
very short time intervals can cause damage to the dim-
ming MOSFET due to excess power dissipation.
V
LED+
MAX16816
AGND
R
OV1
OV
Thermal Shutdown
The MAX16816 contains an internal temperature sensor
that turns off all outputs when the die temperature
exceeds +165°C. Outputs are enabled again when the
die temperature drops below +145°C.
R
OV2
Figure 4. Setting the Overvoltage Threshold
22 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
Boost configuration: In the boost converter, the average
inductor current varies with line and the maximum aver-
age current occurs at low line. For the boost converter,
the average inductor current is equal to the input cur-
rent. In this case the inductance, L, is calculated as:
where V
is the voltage across the load and I
is
OUT
OUT
the output current.
Input Capacitor
An input capacitor connected between V and
ground must be used when configuring the MAX16816
as a buck converter. Use a low-ESR input capacitor
that can handle the maximum input RMS ripple current.
Calculate the maximum allowable RMS ripple using the
following equation:
CC
V
x V
− V
(
)
INMIN
OUT INMIN
L =
V
x f
x ΔI
OUT
SW L
where V
is the minimum input voltage, V
is the
INMIN
output voltage, and f
OUT
is the switching frequency.
SW
I
×
V
× (V
- V
)
OUT
OUT
INMIN
OUT
I
=
IN(RMS)
Buck-boost configuration: In a buck-boost converter
the average inductor current is equal to the sum of the
input current and the load current. In this case the
inductance, L, is:
V
INMIN
In most of the cases, an additional electrolytic capaci-
tor should be added to prevent input oscillations due to
line impedances.
V
x V
INMIN
OUT
L =
When using the MAX16816 in a boost or buck-boost
configuration, the input RMS current is low and the
input capacitance can be small (see the Typical
Operating Circuits).
V
+ V
x f
x ΔI
(
OUT
INMIN
)
SW L
where V
output voltage, and f
is the minimum input voltage, V
is the
INMIN
OUT
is the switching frequency.
SW
Operating the MAX16816 Without the
Dimming Switch
Output Capacitor
The function of the output capacitor is to reduce the
output ripple to acceptable levels. The ESR, ESL, and
the bulk capacitance of the output capacitor contribute
to the output ripple. In most of the applications, the out-
put ESR and ESL effects can be dramatically reduced
by using low-ESR ceramic capacitors. To reduce the
ESL effects, connect multiple ceramic capacitors in
parallel to achieve the required bulk capacitance.
The MAX16816 can also be used in the absence of the
dimming MOSFET. In this case, the PWM dimming per-
formance is compromised but in applications that do
not require dimming the MAX16816 can still be used. A
short circuit across the load will cause the MAX16816
to disable the gate drivers and they will remain off until
the input power is recycled.
Switching Power MOSFET Losses
When selecting MOSFETs for switching, consider the
total gate charge, power dissipation, the maximum
drain-to-source voltage, and package thermal imped-
ance. The product of the MOSFET gate charge and
In a buck configuration, the output capacitance, C , is
F
calculated using the following equation:
(V
− V
) × V
INMAX
OUT OUT
C
≥
F
2
ΔV × 2 × L × V
× f
SW
R
INMAX
R
is a figure of merit, with a lower number signi-
DS(ON)
fying better performance. Select MOSFETs optimized
for high-frequency switching applications.
where ΔV is the maximum allowable output ripple.
R
In a boost configuration, the output capacitance, C , is
F
calculated as:
Layout Recommendations
Typically, there are two sources of noise emission in a
switching power supply: high di/dt loops and high dv/dt
surfaces. For example, traces that carry the drain cur-
rent often form high di/dt loops. Similarly, the heatsink
of the MOSFET connected to the device drain presents a
high dv/dt source; therefore, minimize the surface area of
the heatsink as much as possible. Keep all PCB traces
carrying switching currents as short as possible to mini-
mize current loops. Use ground planes for best results.
(V
− V
) × 2 × I
OUT
INMIN OUT
C
≥
F
ΔV × V
× f
SW
R
OUT
where I
is the output current.
OUT
In a buck-boost configuration, the output capacitance,
C , is calculated as:
F
2 × V
× I
OUT
OUT
C
≥
F
ΔV × (V
+ V
) × f
R
OUT
INMIN SW
______________________________________________________________________________________ 23
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
Careful PCB layout is critical to achieve low switching
1-Wire Interface
losses and clean, stable operation. Use a multilayer
board whenever possible for better noise performance
and power dissipation. Follow these guidelines for
good PCB layout:
EEPROM implementation uses a 1-Wire communica-
tion method. A 1-Wire net-based system consists of
three main elements: a bus master with controlling
software, the wiring and associated connectors, and
1-Wire devices. Data on the 1-Wire net is transferred
with respect to time slots. For example, the master pulls
the bus low and holds it for 15µs or less to write a logic
‘1’, and holds the bus low for at least 60µs to write a
logic ‘0’. During EEPROM programming the MAX16816
is a 1-Wire slave device only. Data and clock signals
are supplied through FAULT.
• Use a large copper plane under the MAX16816
package. Ensure that all heat-dissipating compo-
nents have adequate cooling. Connect the
exposed pad of the device to the ground plane.
• Isolate the power components and high current
MAX816
paths from sensitive analog circuitry.
• Keep the high-current paths short, especially at the
ground terminals. This practice is essential for sta-
ble, jitter-free operation. Keep switching loops short.
MAX16816 1-Wire Function Commands
Table 10 shows the list of 1-Wire function commands
for the MAX16816. Use these commands to start the
programming mode, write to the on-chip EEPROM, and
read EEPROM through the 1-Wire interface.
• Connect AGND, SGND, and QGND to a ground
plane. Ensure a low-impedance connection
between all ground points.
PASS_CODE_ONE: The PASS_CODE_ONE sequence
is the first code that the MAX16816 must receive from
the master. PASS_CODE_ONE must be received within
the initial 8ms programming window after startup.
• Keep the power traces and load connections
short. This practice is essential for high efficiency.
Use thick copper PCBs (2oz vs. 1oz) to enhance
full-load efficiency.
PASS_CODE_TWO: The PASS_CODE_TWO sequence
is the second code that the MAX16816 must receive
during the 8ms programming window. The MAX16816
will start searching for PASS_CODE_TWO only after
PASS_CODE_ONE has been received.
• Ensure that the feedback connection to FB is short
and direct.
• Route high-speed switching nodes away from the
sensitive analog areas.
• To prevent discharge of the compensation capaci-
EXT_EEM_MODE: The EXT_EEM_MODE command
clears the PASS_CODE_ONE and PASS_CODE_TWO
verification register. Use this command to exit program-
ming mode.
tors, C and C , during the off-time of the dimming
1
2
cycle, ensure that the PCB area close to these
components has extremely low leakage.
Discharge of these capacitors due to leakage may
result in degraded dimming performance.
SET_WRITE_EE: The SET_WRITE_EE command is the
write all command for the MAX16816. When the device
detects the SET_WRITE_EE command the write
Table 10. MAX16816 1-Wire Function Commands
DATA BIT CODE
HEX
CODE
COMMAND
D7
D6
D5
D4
D3
D2
D1
D0
PASS_CODE_ONE
PASS_CODE_TWO
EXT_EEM_MODE
SET_WRITE_EE
0
0
0
0
1
0
0
0
1
0
0
1
29h
09h
01h
04h
—
1
0
0
1
0
0
0
0
0
0
0
1
0
0
1
0
0
0
0
0
SET_WRITE_SCH
SET_READ_SCH
ADD
0
ADD
0
ADD
0
ADD
0
DATA
0
DATA
1
DATA
1
DATA
0
06h
24 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
sequence begins. All EEPROM bits are copied to the
EEPROM from the scratchpad with a single
SET_WRITE_EE command. This command also sets an
internal BUSY flag to mask all other incoming signals.
programming purposes. Ensure that V
is greater
CC
than the UVLO threshold because both UVEN and
FAULT are pulled up to 5V. See the Electrical
Characteristic tables for details.
SET_WRITE_SCH: The SET_WRITE_SCH command
transfers data to the scratchpad. The 4 MSBs contain the
register address and the 4 LSBs contain the data to be
written. The internal BUSY flag is not set by this com-
mand. Table 11 shows the MAX16816 EEPROM memory
organization. Use the SET_WRITE_EE command to trans-
fer data from the scratchpad to the EEPROM.
V
CC
SET_READ_SCH: The SET_READ_SCH command is
the command to read data in the scratch pad buffer.
Once the MAX16816 receives the SET_READ_SCH
command, data on the scratchpad register is shifted
out. After 60 clock cycles, the MAX16816 completes
the SET_READ_SCH sequence. The BUSY signal is not
set by this command.
EN
UVEN
μC
MAX16816
READ
DATA IN
FAULT
Programming
To program the MAX16816 on-chip EEPROM with a
pulldown device, directly connect FAULT to the DATA
IN input of a microcontroller (µC). Also, connect FAULT
to the DATA OUT output of a µC using an external
switch (Figure 5). Connect the EN of the µC directly to
UVEN to control the internal timer of the MAX16816 for
WRITE
DATA OUT
Figure 5. Programming Through a FAULT Pin
Table 11. MAX16816 Memory Map (Scratchpad)
SCRATCHPAD
EEPROM ADDRESS
ADDRESS
REGISTER
1h
2h
Reserved
Reserved
Reserved
Reserved
Reserved
14h–23h
24h–27h
28h–2Bh
2Ch–2Fh
30h–33h
34h–37h
38h–3Bh
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
3h
4h
5h
6h–9h
Ah
Binning Adjustment Register
Bh
REG2 Control Register
Ch
Dh
Eh
Reserved
Blanking Time Adjustment Register
Digital Soft-Start Duration Register, Internal Oscillator Enable Bit
Slope Compensation Register
Fh
______________________________________________________________________________________ 25
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
Programming Sequences
The µC (master) starts the communication with the
MAX16816 by pulling UVEN high. The MAX16816 then
does the handshaking with the µC by pulling FAULT low.
Once the µC receives the handshaking signal, it begins
the initialization sequences to reset the 1-Wire interface.
The sequence consists of a reset pulse from the µC fol-
lowed by a presence pulse from the MAX16816. At this
point the µC must send PASS_CODE_ONE and
PASS_CODE_TWO. These pass codes must be received
by the MAX16816 within the 8ms programming slot to
allow the MAX16816 to enter the EE programming mode.
Initialization Procedure
(Reset and Presence Pulses)
All 1-Wire communication with the MAX16816 begins
with an initialization sequence that consists of a Reset
Pulse from the master followed by a Presence Pulse
from the MAX16816 (Figure 6). When the MAX16816
sends the Presence Pulse in response to the Reset
Pulse, it is indicating to the master that it is ready to
receive and transmit data.
During the initialization sequence, the bus master trans-
mits the reset pulse by pulling the 1-Wire bus low for a
minimum of 480µs. The bus master then releases the
bus and goes into receive mode. When the bus is
released, the pullup resistor pulls the 1-Wire bus high.
When the MAX16816 detects this rising edge, it waits
15µs to 60µs and then transmits a Presence Pulse by
pulling the 1-Wire bus low for 60µs to 240µs.
MAX816
1-Wire Signaling
The MAX16816 requires strict protocols to ensure data
integrity. The protocol consists of four types of signal-
ing on one line: reset sequence with Reset Pulse and
Presence Pulse, Write-Zero, Write-One, and Read-Data.
Except for the Presence Pulse, the bus master initiates
all falling edges.
Read and Write Time Slots
The bus master writes data to the MAX16816 during
write time slots and reads data from the MAX16816
during read time slots. One bit of data is transmitted
over the 1-Wire bus per time slot.
Externally pull FAULT below V to indicate a logic-input
IL
low. Release the pulldown device to indicate a logic-
input high. The MAX16816 will pull FAULT low below
V
to indicate a logic-output low. FAULT is pulled high
OL
with an internal 10kΩ resistor above V
to indicate a
OH
logic-output high.
MASTER Tx "RESET PULSE"
MASTER Rx "PRESENCE PULSE"
t
MSP
V
OH
V
OL
OR V
IL
0V
t
RSTL
RESISTOR
MASTER
MAX16816
Figure 6. 1-Wire Initialization Timing
26 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
Write Time Slots
There are two types of write time slots: Write-1 time
slots and Write-0 time slots. The bus master uses a
Write-1 time slot to write a logic ‘1’ to the MAX16816
and a Write-0 time slot to write a logic ‘0’. All write time
slots must be a minimum of 60µs in duration with a min-
imum of a 1µs recovery time between individual Write
slots. Both types of write time slots are initiated by the
master pulling the 1-Wire bus low (Figures 7 and 8).
low. When the bus is released, the pullup resistor will
pull the bus high. To generate a Write-0 time slot, the
bus master must continue to hold the bus low for the
duration of the time slot (at least 60µs) after pulling the
1-Wire bus low. The MAX16816 samples the 1-Wire bus
during a window that lasts from 15µs to 60µs after the
master initiates the Write time slot. If the bus is high
during the samples window, a ‘1’ is written to the
MAX16816. If the line is low, a ‘0’ is written to the
MAX16816.
To generate a Write-1 time slot, the bus master must
release the 1-Wire bus within 15µs after pulling the bus
t
W1L
V
OH
MAX16816
SAMPLING
WINDOW
V
OL
0V
t
REC
t
SLOT
RESISTOR
MASTER
Figure 7. 1-Wire Write-1 Time Slot
t
W0L
V
OH
MAX16816
SAMPLING
WINDOW
V
IL
0V
t
REC
t
SLOT
RESISTOR
MASTER
Figure 8. 1-Wire Write-0 Time Slot
______________________________________________________________________________________ 27
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
Read Time Slots
The MAX16816 can only transmit data to the master
when the master issues read time slots.
on the bus. The MAX16816 transmits a ‘1’ by leaving
the bus high and transmits a ‘0’ by pulling the bus low.
When transmitting a ‘0’, the MAX16816 will release the
bus before the end of the time slot, and the bus will be
pulled back to its high idle state by the pullup resistor.
Output data from the MAX16816 is valid for 15µs after the
falling edge that initiated the read time slot. Therefore, the
master must release the bus and then sample the bus
state within 15µs from the start of the slot.
All read time slots must be a minimum of 60µs in dura-
tion with a minimum of a 1µs recovery time between
slots. A read time slot is initiated by the master device
pulling the 1-Wire bus low for a minimum of 1µs and
then releasing it (Figure 9). After the master initiates the
read time slot, the MAX16816 will transmit a ‘1’ or a ‘0’
MAX816
t
MSR
t
RL
V
OH
MASTER
SAMPLING
WINDOW
V / V
IL OL
0V
t
REC
t
SLOT
RESISTOR
MASTER
MAX16816
Figure 9. 1-Wire Read Time Slot
28 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
Pin Configuration
Chip Information
PROCESS: BiCMOS
TOP VIEW
32
31
30
29
28
27
26
25
+
N.C.
UVEN
N.C.
1
2
3
4
5
6
7
8
24
23
22
21
20
19
DGT
REG1
QGND
SNS-
SNS+
DRI
AGND
REF
MAX16816
DIM
RTSYNC
CLKOUT
18 DRV
17
*EP
SGND
9
10 11 12 13 14 15 16
TQFN
(5mm x 5mm)
*EP = EXPOSED PAD
______________________________________________________________________________________ 29
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
Typical Operating Circuits (continued)
V
IN
R
CS
C
CLMP
C
F
R
UV2
V
CS+
DGT
CS-
LO
CLMP
CC
R
UV1
MAX816
UVEN
REF
R
D
Q
S
LEDs
DRV
C
UVEN
SNS+
R
SENSE
MAX16816
SNS-
R
R
3
QGND
R
DIM
OV1
4
OV
REG2
DRI
FAULT
R
OV2
RTSYNC
COMP
HI
CS
FB
REG1
AGND
SGND
R
T
C
REG2
C
REG1
R1
C2
R2
C1
BOOST CONFIGURATION
30 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
Typical Operating Circuits (continued)
V
IN
R
CS
C
CLMP
R
UV2
C
F
V
HI
DGT
CS- CS+
LO CLMP
CC
Q
S
R
D
FAULT
UVEN
DRV
R
UV1
LEDs
SNS+
R
C
UVEN
SENSE
SNS-
MAX16816
QGND
DIM
T
DIM
REG1
R
C
REG1
RTSYNC
COMP
OV
DRI
CS
FB
AGND
SGND
REG2
R1
C
REG2
C2
R2
C1
BUCK CONFIGURATION
______________________________________________________________________________________ 31
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
MAX816
32 ______________________________________________________________________________________
Programmable Switch-Mode LED Driver
with Analog-Controlled PWM Dimming
MAX816
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 33
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
Heaney
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