MP3389EY-Z [MPS]
LED Driver, 12-Segment, PDSO28, MS-013AE, SOIC-28;
| 型号： | MP3389EY-Z |
| 厂家： | 
MONOLITHIC POWER SYSTEMS |
| 描述： | LED Driver, 12-Segment, PDSO28, MS-013AE, SOIC-28 驱动 光电二极管 接口集成电路 |
| 文件： | 总16页 (文件大小：385K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MP3389
12–String, Step-up
White LED Driver
The Future of Analog IC Technology
DESCRIPTION
FEATURES
•
•
•
•
•
High Efficiency and Small Size
The MP3389 is a step-up controller with 12-
channel current sources designed for driving
the WLED arrays for large size LCD panel
backlighting applications.
5V to 28V Input Voltage Range
Balanced Driver for 12 Strings of WLEDs
Maximum 60mA for Each String
2.5% Current Matching Accuracy Between
Strings
The MP3389 uses current mode, fixed frequency
architecture. The switching frequency is
programmable by an external frequency setting
resistor. It drives an external MOSFET to boost
up the output voltage from a 5V to 28V input
supply. The MP3389 regulates the current in
each LED string to the programmed value set by
an external current setting resistor.
•
•
•
•
•
•
•
Programmable Switching Frequency
PWM or DC Input Burst PWM Dimming
Open and Short LED protection
Programmable Over-voltage Protection
Under Voltage Lockout
Thermal Shutdown
28-pin TSSOP and 28-pin SOIC Package
The MP3389 applies 12 internal current
sources for current balance. And the current
matching can achieve 2.5% regulation accuracy
between strings. Its low 550mV regulation
voltage on LED current sources reduces power
loss and improves efficiency.
APPLICATIONS
•
•
•
Desktop LCD Flat Panel Displays
Flat Panel Video Displays
LCD TVs and Monitors
All MPS parts are lead-free and adhere to the RoHS directive. For MPS green
status, please visit MPS website under Quality Assurance. “MPS” and “The
Future of Analog IC Technology” are Registered Trademarks of Monolithic
Power Systems, Inc.
PWM dimming is implemented with external
PWM input signal or DC input signal. The
dimming PWM signal can be generated internally,
and the dimming frequency is programmed by
an external setting capacitor.
TYPICAL APPLICATION
D1
M1
L1
VIN
CIN
COUT
5V~28V
R1
R2
2
3
27
26
24
28
25
23
22
21
20
19
18
17
16
15
VIN
VFAULT
GATE
ISENSE
NC
C
VCC
M2
VCC
C
COMP
RCOMP
4
COMP
EN
R
SENSE
5
Enable
8
OSC
PGND
OVP
R
OSC
1
NC
VCC
10
7
BOSC
GND
DBRT
ISET
LED12
LED11
LED10
LED9
LED1
R
BOSC
C
BOSC
MP3389
LED2
LED3
LED4
LED5
LED6
LED7
LED8
6
DIMMING
R
SET
9
11
12
13
14
MP3389 Rev. 1.04
3/27/2013
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
1
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
ORDERING INFORMATION
Part Number*
MP3389EF
MP3389EY
Package
TSSOP28
SOIC28
Top Marking
3389EF
3389EY
*For Tape & Reel, add suffix –Z (eg. MP3389EF–Z).
For RoHS compliant packaging, add suffix –LF (eg. MP3389EF–LF–Z)
**For Tape & Reel, add suffix –Z (eg. MP3389EY–Z).
For RoHS compliant packaging, add suffix –LF (eg. MP3389EY–LF–Z)
PACKAGE REFERENCE
TOP VIEW
NC
VIN
1
2
3
4
5
6
7
8
9
28 NC
27 VFAULT
26 GATE
25 PGND
24 ISENSE
23 OVP
VCC
COMP
EN
DBRT
GND
OSC
ISET
22 LED1
21 LED2
20 LED3
19 LED4
18 LED5
17 LED6
16 LED7
15 LED8
BOSC 10
LED12 11
LED11 12
LED10 13
LED9 14
TSSOP28
SOIC28
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance (4)
θJA
θJC
VIN .................................................-0.3V to +30V
TSSOP28................................32 ....... 6....°C/W
SOIC28 ..................................60 ...... 30...°C/W
V
VFAULT...........................................VIN - 6V to VIN
VGATE ..............................................-0.5V to 6.3V
LED1 to VLED12 ..................................-1V to +50V
V
Notes:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ (MAX), the junction-to-
ambient thermal resistance θJA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD (MAX) = (TJ
(MAX)-TA)/θJA. Exceeding the maximum allowable power
dissipation will cause excessive die temperature, and the
regulator will go into thermal shutdown. Internal thermal
shutdown circuitry protects the device from permanent
damage.
All Other Pins...............................-0.3V to +6.3V
(2)
Continuous Power Dissipation (TA = +25°C)
TSSOP28……………………………… ...3.9W
SOIC28………………………………… ...2.1W
Junction Temperature...............................150°C
Lead Temperature ....................................260°C
Storage Temperature............... -65°C to +150°C
3) The device is not guaranteed to function outside of its
operation conditions.
4) Measured on JESD51-7, 4-layer PCB.
Recommended Operating Conditions (3)
Supply Voltage VIN ..............................5V to 28V
LED Current (Backlight) .............10mA to 60mA
Operating Junction Temp. (TJ). -40°C to +125°C
MP3389 Rev. 1.04
3/27/2013
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
2
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
ELECTRICAL CHARACTERISTICS
VIN =12V, VEN = 5V, TA = +25°C, unless otherwise noted.
Parameters
Symbol Condition
Min
Typ
Max
Units
V
Operating Input Voltage
Supply Current (Quiescent)
VIN
4.5
28
VIN=12V, VEN=5V, no load with
switching
IQ
IST
4
mA
Supply Current (Shutdown)
LDO Output Voltage
VEN=0V, VIN=12V
2
μA
VEN=5V,
0<IVCC<10mA
6V<VIN<28V,
VCC
4.5
3.4
5
5.5
4.3
V
Input UVLO Threshold
Input UVLO Hysteresis
EN High Voltage
VIN_UVLO Rising Edge
3.9
V
mV
V
200
VEN_HIGH VEN Rising
VEN_LOW VEN Falling
1.6
EN Low Voltage
0.6
V
STEP-UP CONVERTER
Gate
(Sourcing)
Gate
(Sinking)
Driver
Impedance
VCC=5V,VGATE=5V
4
2
Ω
Ω
Driver
Impedance
VCC=5V,IGATE=10mA
ROSC= 115kΩ
530
160
1.18
590
180
1.23
650
200
1.28
kHz
kHz
V
Switching Frequency
fSW
R
OSC= 374kΩ
OSC Voltage
VOSC
TON_MIN
DMAX
PWM Mode,
Minimum On Time
100
ns
when no pulse skipping happens
Max Duty Cycle
Maximum Duty Cycle
ISENSE Limit
Leading Edge Blanking Time (6)
90
%
mV
ns
175
220
250
265
TLEB
PWM DIMMING
DBRT Leakage Current
BOSC Frequency
IDBRT_LK
FBOSC
IBOSC
-5
+5
2
μA
kHz
μA
CBOSC=2.2nF
1.2
1.6
7.5
BOSC Output Current
LED CURRENT REGULATION
ISET Voltage
6.37
8.63
VISET
ILED
1.20
29.6
1.22 1.245
V
LEDX Average Current
Current Matching (5)
RISET=40kꢀ
ILED=30.5mA
ILED=30.5mA
30.5
31.4
2.5
mA
%
LEDX Regulation Voltage
PROTECTION
VLEDX
410
550
690
mV
OVP Over Voltage Threshold
VOVP_OV Rising Edge
1.20
1.23
1.26
V
MP3389 Rev. 1.04
3/27/2013
www.MonolithicPower.com
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© 2013 MPS. All Rights Reserved.
3
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
ELECTRICAL CHARACTERISTICS (continued)
VIN =12V, VEN = 5V, TA = +25°C, unless otherwise noted.
Parameters
Symbol Condition
Min
50
Typ
70
Max Units
OVP UVLO threshold
VOVP_UV Step-up Converter Fails
90
5.9
220
mV
V
LEDX Over Voltage Threshold
LEDX UVLO Threshold
Thermal Shutdown Threshold
VFAULT Pull Down Current
VLEDX_OV VIN>5.5V
5.1
140
5.5
180
130
55
VLEDX_UV
TST
mV
℃
IFAULT
40
70
μA
VFAULT Blocking-Off Voltage
(with Respect to VIN)
VFAULT
VIN =12V, VIN-VFAULT
5.3
5.8
6.3
V
Notes:
5) Matching is defined as the difference of the maximum to minimum current divided by 2 times average currents.
6) Guarantee by design.
MP3389 Rev. 1.04
3/27/2013
www.MonolithicPower.com
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© 2013 MPS. All Rights Reserved.
4
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
PIN FUNCTIONS
Pin # Name Description
1
NC
No Connect.
Supply Input. VIN supplies the power to the chip, as well as the step-up converter switch. Drive
VIN with a 5V to 28V power source. Must be locally bypassed.
2
VIN
The Internal 5V Linear Regulator Output. VCC provides power supply for the internal MOSFET
3
VCC switch gate driver and the internal control circuitry. Bypass VCC to GND with a ceramic
capacitor.
Step-up Converter Compensation Pin. This pin is used to compensate the regulation control
loop. Connect a capacitor or a series RC network from COMP to GND.
4
5
COMP
EN
Enable Control Input. Do not let this pin floating.
Brightness Control Input. To use external PWM dimming mode, apply a PWM signal on this pin
for brightness control. To use DC input PWM dimming mode, apply a DC voltage range from
0.2V to 1.2V on this pin linearly to set the internal dimming duty cycle from 0% to 100%. The
MP3389 has positive dimming polarity on DBRT.
6
DBRT
7
8
GND Analog Ground.
Switching Frequency Set. Connect a resistor between OSC and GND to set the step-up
OSC converter switching frequency. The voltage at this pin is regulated to 1.23V. The clock frequency
is proportional to the current sourced from this pin.
LED Current Set. Tie a current setting resistor from this pin to ground to program the current in
each LED string. The MP3389 regulates the voltage across the current setting resistor. The
regulation voltage is 1.22V. The proportion of the current through the ISET resistor and the LED
9
ISET
current is 1:1000.
Dimming Repetition Set. This is the timing pin for the oscillator to set the dimming frequency. To
use DC input PWM dimming mode, connect a capacitor from this pin to GND to set the internal
BOSC dimming frequency. A saw-tooth waveform is generated on this pin. To use external PWM
dimming mode, connect a 100kꢀ resistor from this pin to GND, and apply the PWM signal on
DBRT pin.
10
LED String 12 Current Input. This pin is the open-drain output of an internal dimming control
LED12 switch. Connect the LED String 12 cathode to this pin. If this string is not used, connect Vin to
this pin.
11
12
13
14
LED String 11 Current Input. This pin is the open-drain output of an internal dimming control
LED11 switch. Connect the LED String 11 cathode to this pin. If this string is not used, connect Vin to
this pin.
LED String 10 Current Input. This pin is the open-drain output of an internal dimming control
LED10 switch. Connect the LED String 10 cathode to this pin. If this string is not used, connect Vin to
this pin.
LED String 9 Current Input. This pin is the open-drain output of an internal dimming control
LED9 switch. Connect the LED String 9 cathode to this pin. If this string is not used, connect Vin to this
pin.
MP3389 Rev. 1.04
3/27/2013
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
5
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
PIN FUNCTIONS (continued)
Pin #
Name
Description
LED String 8 Current Input. This pin is the open-drain output of an internal dimming
control switch. Connect the LED String 8 cathode to this pin. If this string is not used,
connect Vin to this pin.
15
LED8
LED String 7 Current Input. This pin is the open-drain output of an internal dimming
control switch. Connect the LED String 7 cathode to this pin. If this string is not used,
connect Vin to this pin.
LED String 6 Current Input. This pin is the open-drain output of an internal dimming
control switch. Connect the LED String 6 cathode to this pin. If this string is not used,
connect Vin to this pin.
LED String 5 Current Input. This pin is the open-drain output of an internal dimming
control switch. Connect the LED String 5 cathode to this pin. If this string is not used,
connect Vin to this pin.
LED String 4 Current Input. This pin is the open-drain output of an internal dimming
control switch. Connect the LED String 4 cathode to this pin. If this string is not used,
connect Vin to this pin.
16
17
18
19
20
LED7
LED6
LED5
LED4
LED3
LED String 3 Current Input. This pin is the open-drain output of an internal dimming
control switch. Connect the LED String 3 cathode to this pin. If this string is not used,
connect Vin to this pin.
LED String 2 Current Input. This pin is the open-drain output of an internal dimming
control switch. Connect the LED String 2 cathode to this pin. If this string is not used,
connect Vin to this pin.
LED String 1 Current Input. This pin is the open-drain output of an internal dimming
control switch. Connect the LED String 1 cathode to this pin. If this string is not used,
connect Vin to this pin.
21
22
LED2
LED1
Over-voltage Protection Input. Connect a resistor divider from output to this pin to
program the OVP threshold. When this pin voltage reaches 1.23V, the MP3389 triggers
OV Protection mode.
23
24
OVP
Current Sense Input. During normal operation, this pin senses the voltage across the
ISENSE external inductor current sensing resistor for peak current mode control and also to limit
the inductor current during every switching cycle.
25
26
PGND
GATE
Step-up Converter Power Ground.
Step-up Converter Power Switch Gate Output. This pin drives the external power N-MOS
device.
Fault Disconnection Switch Gate Output. When the system starts up normally, this pin
27
28
VFAULT smoothly turns on the external PMOS. When the MP3389 is disabled, the external
PMOS is turned off to disconnect the input and output.
NC
No Connect.
MP3389 Rev. 1.04
3/27/2013
www.MonolithicPower.com
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© 2013 MPS. All Rights Reserved.
6
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
TYPICAL PERFORMANCE CHARACTERISTICS
VIN =12V, 14 LEDs in series, 12 strings parallel, 20mA/string, unless otherwise noted.
Efficiency vs. Input Voltage
Steady State
Vin Startup
0.95
0.9
V
V
SW
SW
20V/div.
20V/div.
0.85
0.8
V
(AC)
1V/div.
OUT
V
OUT
20V/div.
V
LED1
1V/div.
V
IN
0.75
0.7
5V/div.
LED
200mA/div.
I
I
LED1
20mA/div.
6
12
18
24
30
INPUT VOLTAGE (V)
Ven Startup
V
V
SW
V
SW
SW
20V/div.
20V/div.
20V/div.
V
OUT
V
V
20V/div.
OUT
OUT
20V/div.
V
20V/div.
PWM1
5V/div.
V
BOSC
V
EN
500mV/div.
I
LED
5V/div.
I
200mA/div.
LED
I
LED
200mA/div.
200mA/div.
Open LED Protection
Short LED Protection
Short LED Protection
open all LED strings at working
short V
to LEDx at working
short V
to GND at working
OUT
OUT
V
V
SW
V
SW
SW
20V/div.
20V/div.
20V/div.
V
OUT
50V/div.
V
OUT
V
OUT
20V/div.
20V/div.
V
LED1
V
V
FAULT
FAULT
20V/div.
5V/div.
5V/div.
I
LED
I
LED
I
LED
100mA/div.
200mA/div.
200mA/div.
MP3389 Rev. 1.04
3/27/2013
www.MonolithicPower.com
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© 2013 MPS. All Rights Reserved.
7
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
FUNCTION DIAGRAM
VFAULT
VCC
Regulator
VIN
GND
-
Control
Logic
GATE
+
PWM
Comparator
Current Sense
Amplifier
ISENSE
PGND
+
-
OV
Comparator
+
-
OVP
Oscillator
OSC
1.23V
LED OV
Comparator
-
5.5V
Short String
Protection
+
-
Max
Min
Feedback
Control
EA
+
COMP
EN
600mV
Enable
Control
LED1
+
1.22V
-
ISET
Current Control
DPWM
Oscillator
BOSC
DBRT
DPWM
Comparator
LED12
-
+
Figure 1—MP3389 Function Block Diagram
MP3389 Rev. 1.04
3/27/2013
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8
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
added to the output of the current sense amplifier
and the result is fed into the PWM comparator.
When this result voltage reaches the output
voltage of the error amplifier (VCOMP) the external
MOSFET is turned off.
OPERATION
The MP3389 employs a programmable constant
frequency, peak current mode step-up converter
and 12-channels regulated current sources to
regulate the array of 12 strings white LEDs. The
operation of the MP3389 can be understood by
referring to the block diagram of Figure 1.
The voltage at the output of the internal error
amplifier is an amplified signal of the difference
between the 550mV reference voltage and the
feedback voltage. The converter automatically
chooses the lowest active LEDX pin voltage for
providing enough bus voltage to power all the
LED arrays.
Internal 5V Regulator
The MP3389 includes an internal linear regulator
(VCC). When VIN is greater than 5.5V, this
regulator offers a 5V power supply for the internal
MOSFET switch gate driver and the internal
control circuitry. The VCC voltage drops to 0V
when the chip shuts down. In the application of
VIN smaller than 5.5V, tie VCC and VIN together.
The MP3389 features Under Voltage Lockout.
The chip is disabled until VCC exceeds the
UVLO threshold. And the hysteresis of UVLO is
approximately 200mV.
If the feedback voltage drops below the 550mV
reference, the output of the error amplifier
increases. It results in more current flowing
through the power FET, thus increasing the
power delivered to the output. In this way it forms
a close loop to make the output voltage in
regulation.
At light-load or Vout near to Vin operation, the
converter runs into the pulse-skipping mode, the
FET is turned on for a minimum on-time of
approximately 100ns, and then the converter
discharges the power to the output in the remain
period. The external MOSFET will keep off until
the output voltage needs to be boosted again.
System Startup
When the MP3389 is enabled, the chip checks
the topology connection first. The VFAULT pin
drives the external Fault Disconnection PMOS to
turn on slowly. Then the chip monitors the OVP
pin to see if the Schottky diode is not connected
or the boost output is short to GND. If the OVP
voltage is lower than 70mV, the chip will be
disabled and the external PMOS is turned off
together. The MP3389 will also check other
safety limits, including UVLO and OTP after the
OVP test is passed. If they are all in function, it
then starts boosting the step-up converter with an
internal soft-start.
Dimming Control
The MP3389 provides two PWM dimming
methods: external PWM signal or DC input PWM
Dimming mode (see Figure 2). Both methods
results in PWM chopping of the current in the
LEDs for all 12 channels to provide LED control.
DPWM
Comparator
Ex-PWM Input
DPWM Output
-
It is recommended on the start up sequence that
the enable signal comes after input voltage and
PWM dimming signal established.
+
DBRT
Step-up Converter
DPWM
Oscillator
The
converter
operation
frequency
is
programmable (from 100kHz to 500kHz) with a
external set resistor on OSC pin, which is helpful
for optimizing the external components sizes and
improving the efficiency.
BOSC
C
BOSC
Figure 2—PWM Dimming Method
At the beginning of each cycle, the external
MOSFET is turned with the internal clock. To
prevent sub-harmonic oscillations at duty cycles
greater than 50 percent, a stabilizing ramp is
When bias the BOSC pin to a DC level, applying
a PWM signal to the DBRT pin to achieve the
PWM dimming. A DC analog signal can be
MP3389 Rev. 1.04
3/27/2013
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© 2013 MPS. All Rights Reserved.
9
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
directly applied to the DBRT pin to modulate the
The MP3389 always tries to light at least one
string and if all strings in use are open, the
MP3389 shuts down the step-up converter. The
part will maintain mark-off information until the
part shuts down.
LED current. And the DC signal is then converted
to a DPWM dimming signal at the setting
oscillation frequency.
The brightness of the LED array is proportional to
the duty cycle of the DPWM signal. The DPWM
signal frequency is set by the cap at the BOSC
pin.
Short String Protection
The MP3389 monitors the LEDX pin voltage to
judge if the short string occurs. If one or more
strings are short, the respective LEDX pins will
be pulled up to the boost output and tolerate high
voltage stress. If the LEDX pin voltage is higher
than 5.5V, the short string condition is detected
on the respective string. When the short string
fault (LEDX over-voltage fault) continues for
greater than 512 switching clocks, the string is
marked off and disabled. Once a string is marked
off, its current regulation is forced to disconnect
from the output voltage loop regulation. The
marked-off LED strings will be shut off totally until
the part restarts. If all strings in use are short, the
MP3389 will shut down the step-up converter.
Open String Protection
The open string protection is achieved through
the over voltage protection. If one or more strings
are open, the respective LEDX pins are pulled to
ground and the IC keeps charging the output
voltage until it reach OVP threshold. Then the
part will mark off the open strings whose LEDX
pin voltage is less than 180mV. Once the mark-
off operation completes, the remaining LED
strings will force the output voltage back into tight
regulation. The string with the highest voltage
drop is the ruling string during output regulation.
MP3389 Rev. 1.04
3/27/2013
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10
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
VOUT ×ILOAD(MAX)
APPLICATION INFORMATION
I
=
IN(MAX)
V ×η
IN
Selecting the Switching Frequency
ΔI = (30%~40%)×I
The switching frequency of the step-up converter
is programmable from 100kHz to 500kHz. A
oscillator resistor on OSC pin sets the internal
oscillator frequency for the step-up converter
according to the equation:
IN(MAX)
Where VIN is the minimum input voltage, fSW is the
switching frequency, ILOAD(MAX) is the maximum
load current, ∆I is the peak-to-peak inductor
ripple current and ηis the efficiency.
fSW = 67850 / ROSC（kꢀ）
The switch current is usually used for the peak
current mode control. In order to avoid hitting the
current limit, the voltage across the sensing
resistor RSENSE should be less than 80% of the
worst case current limit voltage, VSENSE.
For ROSC=191kꢀ, the switching frequency is set
to 355 kHz.
Setting the LED Current
The LED string currents are identical and set
through the current setting resistor on the ISET
pin.
0.8× VSENSE
RSENSE
=
IL(PEAK)
ILED = 1000 x 1.22V / RSET
Where IL(PEAK) is the peak value of the inductor
current. VSENSE is shown in Figure 3.
For RSET=60.4kꢀ, the LED current is set to 20mA.
The ISET pin can not be open.
V
vs. Duty Cycle
Selecting the Input Capacitor
SENSE
The input capacitor reduces the surge current
drawn from the input supply and the switching
noise from the device. The input capacitor
impedance at the switching frequency should be
less than the input source impedance to prevent
high frequency switching current from passing
through the input. Ceramic capacitors with X5R
or X7R dielectrics are highly recommended
because of their low ESR and small temperature
coefficients. For most applications, a 4.7μF
ceramic capacitor paralleled a 220uF electrolytic
capacitor is sufficient.
700
600
500
400
300
200
100
0
Selecting the Inductor and Current Sensing
Resistor
0
10 20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)
The inductor is required to force the higher output
voltage while being driven by the input voltage. A
larger value inductor results in less ripple current,
resulting in lower peak inductor current and
reducing stress on the internal N-Channel
MOSFET. However, the larger value inductor has
a larger physical size, higher series resistance,
and lower saturation current.
Figure 3—VSENSE vs Duty Cycle
Selecting the Power MOSFET
The MP3389 is capable of driving a wide variety
of N-Channel power MOSFETS. The critical
parameters of selection of a MOSFET are:
1. Maximum drain to source voltage, VDS(MAX)
2. Maximum current, ID(MAX)
Choose an inductor that does not saturate under
the worst-case load conditions. A good rule for
determining the inductance is to allow the peak-
to-peak ripple current to be approximately 30% to
40% of the maximum input current. Calculate the
required inductance value by the equation:
V ×(VOUT − V )
3. On-resistance, RDS(ON)
4. Gate source charge QGS and gate drain
charge QGD
Total gate charge, QG
5.
IN
IN
L =
VOUT × fSW × ΔI
MP3389 Rev. 1.04
3/27/2013
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MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
Ideally, the off-state voltage across the MOSFET
For extended knowledge of the power loss
estimation, readers should refer to the book
“Power MOSFET Theory and Applications”
written by Duncan A. Grant and John Gowar.
is equal to the output voltage. Considering the
voltage spike when it turns off, VDS(MAX) should be
greater than 1.5 times of the output voltage.
The maximum current through the power
MOSFET happens when the input voltage is
minimum and the output power is maximum. The
maximum RMS current through the MOSFET is
given by
The total gate charge, QG, is used to calculate
the gate drive loss. The expression is
PDR = QG × VDR × fSW
Where VDR is the drive voltage.
Selecting the Output Capacitor
IRMS(MAX) = IIN(MAX) × DMAX
The output capacitor keeps the output voltage
ripple small and ensures feedback loop stability.
The output capacitor impedance should be low at
the switching frequency. Ceramic capacitors with
X7R dielectrics are recommended for their low
ESR characteristics. For most applications, a
4.7μF ceramic capacitor paralleled 10uF
electrolytic capacitor will be sufficient.
Where:
VOUT − VIN(MIN)
DMAX
≈
VOUT
The current rating of the MOSFET should be
greater than 1.5 times IRMS,
The on resistance of the MOSFET determines
the conduction loss, which is given by:
Setting the Over Voltage Protection
The open string protection is achieved through
the over voltage protection (OVP). In some cases,
an LED string failure results in the feedback
voltage always zero. The part then keeps
boosting the output voltage higher and higher. If
the output voltage reaches the programmed OVP
threshold, the protection will be triggered.
2
Pcond = IRMS × RDS(on) × k
Where k is the temperature coefficient of the
MOSFET.
The switching loss is related to QGD and QGS1
which determine the commutation time. QGS1 is
the charge between the threshold voltage and
the plateau voltage when a driver charges the
gate, which can be read in the chart of VGS vs. QG
of the MOSFET datasheet. QGD is the charge
during the plateau voltage. These two
parameters are needed to estimate the turn on
and turn off loss.
To make sure the chip functions properly, the
OVP setting resistor divider must be set with a
proper value. The recommended OVP point is
about 1.2 times higher than the output voltage for
normal operation.
VOVP=1.23V*(R1+R2)/R2
Selecting Dimming Control Mode
QGS1 × RG
The MP3389 provides 2 different dimming
methods
PSW
=
× VDS × IIN × fSW
× VDS × IIN × fSW
+
VDR − VTH
QGD × RG
VDR − VPLT
1. Direct PWM Dimming
An external PWM dimming signal is employed to
achieve PWM dimming control. Connect a 100kꢀ
resistor from BOSC pin to GND and apply the
100Hz to 2kHz PWM dimming signal to DBRT
pin. The minimum recommended amplitude of
the PWM signal is 1.2V. The low level should
less than 0.4V. (See Figure 4).
Where VTH is the threshold voltage, VPLT is the
plateau voltage, RG is the gate resistance, VDS is
the drain-source voltage. Please note that the
switching loss is the most difficult part in the loss
estimation. The formula above provides a simple
physical expression. If more accurate estimation
is required, the expressions will be much more
complex.
MP3389 Rev. 1.04
3/27/2013
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MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
Layout Considerations
BOSC
Careful attention must be paid to the PCB board
R1
100k
layout and components placement. Proper layout
of the high frequency switching path is critical to
MP3389
PWM Dimming
100Hz~2kHz
prevent noise and electromagnetic interference
DBRT
problems. The loop of external MOSFET (M2),
output diode (D1), and output capacitor (C5) is
flowing with high frequency pulse current. it must
Figure 4—Direct PWM Dimming
be as short as possible (See Figure 6).
Table 1 shows the PWM dimming duty Range
with different PWM dimming frequency.
Tab 1 The Range of PWM Dimming Duty
fpwm(Hz)
100<f≤200
200<f≤500
500<f≤1k
1k<f≤2k
Dmin
0.30%
0.75%
1.50%
3.00%
7.50%
15.00%
30.00%
Dmax
100%
100%
100%
100%
100%
100%
100%
2k<f≤5k
5k<f≤10k
10k<f≤20k
2. DC Input PWM Dimming
To apply DC input PWM dimming, apply an
analog signal (range from 0.2 V to 1.2V) to the
DBRT pin to modulate the LED current directly. If
the PWM is applied with a zero DC voltage, the
PWM duty cycle will be 0%. If the DBRT pin is
applied with a DC voltage>1.2V, the output will
be 100% (See Figure 5). The capacitor on BOSC
pin set the frequency of internal triangle
waveform according to the equation:
Figure 6—Layout Consideration
The IC exposed pad is internally connected to
GND pin, and all logic signals are refer to the
GND. The PGND should be externally connected
to GND and is recommended to keep away from
the logic signals.
External MOSFET for Short Protection
When output voltage is higher than rating of
LED1-12 pins, external MOSFET is needed for
each LED channel to avoid destroying LED1 -12
pins. (See Figure 8 for 4 channels application)
The rating of MOSFET must be higher than 1.2*
F
UNITE = 3.5μF / CUNITE
BOSC
C1
MP3389
VOUT t and more than 1.2* ILED.
DC Signal
DBRT
Figure 5—DC input PWM Dimming
MP3389 Rev. 1.04
3/27/2013
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13
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
TYPICAL APPLICATION CIRCUIT
L1
M1
D1
14S 12P 20mA
8V-28V
VIN
C3
C13
C16
AM4499P
F1
B180
LED+
C1
C2
NC
C10
NC
R26
LED1
LED2
LED3
LED4
LED5
LED6
C17
5.6nF
NC
R51
432k
C15
R20
10
R11
0
C12
NC
GND
GND
GND
GND
M2 AM4490N
GND
GND
GND
U1
LED7
2
3
27
26
24
28
25
23
22
21
20
19
18
17
16
15
R54
10k
R22
0
VIN
VFAULT
LED8
C14
100pF
R53
10k
LED9
VCC
GATE
ISENSE
NC
LED10
LED11
LED12
C9
R15
4
COMP
EN
R1
2k
C4
GND
GND
R24
0.05
R25
NC
100nF
0
5
EN
8
R4
20k
C18
OSC
PGND
OVP
R13
GND
191k
1
NC
GND
R27
R28
R29
R30
R31
R32
R33
R34
R35
R36
R37
R38
0
0
0
0
0
0
0
0
0
0
0
0
GND
10
7
BOSC
GND
LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8
R8
100k
C6
NC
MP3389
R2
2k
GND
6
NET00016
DBRT
ISET
DIMMING
R16
9
R5
20k
60.4k
GND
11
12
13
14
LED12
LED11
LED10
LED9
GND
Figure 7—Drive 14 LEDs in Series, 12 Strings 20mA/string for Monitor Backlighting
L1
M1
D1
8V-28V
VIN
18S 4P 60mA
C3
C13
C16
AM4499P
F1
B180
LED+
C1 C2
NC
C10
NC
R26
NC
C17
5.6nF
R51
432k
C15
R20
10
R11
0
C12
NC
GND
GND
GND
GND
M2 AM4490N
GND
GND
GND
U1
2
3
27
26
24
28
25
23
22
21
20
19
18
17
16
15
R54
10k
R22
0
VIN
VFAULT
C14
100pF
R53
10k
VCC
GATE
ISENSE
NC
C9
R15
4
COMP
EN
R1
2k
C4
GND
GND
R24
0.05
R25
NC
100nF
0
5
EN
8
LED1
LED2
LED3
LED4
R4
20k
C18
OSC
PGND
OVP
R13
191k
GND
1
NC
GND
R27
R28
R29
R30
R31
R32
R33
R34
R35
R36
R37
R38
0
0
0
0
0
0
0
0
0
0
0
0
GND
10
7
BOSC
GND
LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8
M3
M4
R8
100k
C6
NC
MP3389
R2
2k
GND
6
NET00016
DBRT
ISET
DIMMING
R16
9
R5
20k
60.4k
GND
11
12
13
14
LED12
LED11
LED10
LED9
GND
M3-M6: AM3490N 100V/1A TSOP6
M5
M6
VIN
R39
0
R40
NC
GND
Figure 8 – Drive 18LEDs in Series, 4 strings 60mA/string
Note: For Vin>15V application, use R139 and R40(10kΩ) divider to make a 15V bias voltage for M3-M6.
MP3389 Rev. 1.04
3/27/2013
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
14
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
PACKAGE INFORMATION
TSSOP28
5.90
TYP
0.65
BSC
9.60
9.80
0.40
TYP
28
15
1.60
TYP
3.20 5.80
TYP TYP
4.30
4.50
6.20
6.60
PIN 1 ID
1
14
TOP VIEW
RECOMMENDED LAND PATTERN
0.80
1.05
1.20 MAX
SEATING PLANE
0.09
0.20
0.19
0.30
0.00
0.15
0.65 BSC
SEE DETAIL"A"
SIDE VIEW
FRONT VIEW
GAUGE PLANE
0.25 BSC
5.70
6.10
0.45
0.75
0o-8o
D揂ETAIL
2.60
3.10
NOTE:
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,
PROTRUSION OR GATE BURR.
3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH
OR PROTRUSION.
4) LEAD COPLANARITY(BOTTOM OF LEADS AFTER FORMING)
SHALL BE0.10 MILLIMETERS MAX.
5) DRAWING CONFORMS TO JEDEC MO-153, VARIATION AET.
6) DRAWING IS NOT TO SCALE.
BOTTOM VIEW
MP3389 Rev. 1.04
3/27/2013
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© 2013 MPS. All Rights Reserved.
15
MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
PACKAGE INFORMATION
SOIC28
NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third
party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not
assume any legal responsibility for any said applications.
MP3389 Rev. 1.04
3/27/2013
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
16
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