MAX1576ETG+G104 [MAXIM]
LED Driver, 8-Segment, BICMOS, 4 X 4 MM, 0.80 MM HEIGHT, ROHS COMPLIANT, MO-220WGGD-2, TQFN-24;
| 型号： | MAX1576ETG+G104 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | LED Driver, 8-Segment, BICMOS, 4 X 4 MM, 0.80 MM HEIGHT, ROHS COMPLIANT, MO-220WGGD-2, TQFN-24 驱动 信息通信管理 接口集成电路 |
| 文件： | 总16页 (文件大小：362K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3326; Rev 1; 8/05
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
General Description
Features
The MAX1576 charge pump drives up to 8 white LEDs
with regulated constant current for uniform intensity.
The main group of LEDs (LED1–LED4) can be driven
up to 30mA per LED for backlighting. The flash group
of LEDs (LED5–LED8) are independently controlled and
can be driven up to 100mA per LED (or 400mA total).
By utilizing adaptive 1x/1.5x/2x charge-pump modes
and very-low-dropout current regulators, the MAX1576
achieves high efficiency over the full 1-cell lithium-bat-
tery voltage range. The 1MHz fixed-frequency switch-
ing allows for tiny external components, and the
regulation scheme is optimized to ensure low EMI and
low input ripple.
♦ Powers Up to 8 LEDs
Up to 30mA/LED Drive for Backlight
Up to 400mA Total Drive for Flash
♦ 85% Average Efficiency (P
/ P
) Over Li+
BATT
LED
Battery Discharge
♦ 0.7% Typical LED Current Matching
♦ Adaptive 1x/1.5x/2x Mode Switchover
♦ Flexible Brightness Control
Single-Wire, Serial Pulse Interface (5% to 100%)
2-Bit (3 Levels) Logarithmic Logic
♦ Low Input Ripple and EMI
The MAX1576 uses two external resistors to set the
main and flash full-scale (100%) LED currents. Four
control pins are used for LED dimming by either serial
control or 2-bit logic per group. ENM1 and ENM2 set
the main LEDs to 10%, 30%, or 100% of full scale.
ENF1 and ENF2 set the flash LEDs to 20%, 40%, or
100% of full scale. In addition, connect either pair of
control pins together for single-wire, serial pulse dim-
ming control.
♦ Low 0.1µA Shutdown Current
♦ 2.7V to 5.5V Supply Voltage Range
♦ Soft-Start Limits Inrush Current
♦ Output Overvoltage Protection
♦ Thermal-Shutdown Protection
♦ 24-Pin Thin QFN, 4mm x 4mm Package
The MAX1576 is available in a 24-pin thin QFN, 4mm x
4mm package (0.8mm max height).
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
Applications
24 Thin QFN 4mm x
4mm (T2444-4)
Camera Phones
MAX1576ETG
-40°C to +85°C
LCD Backlights
24 Thin QFN 4mm x
4mm (T2444-4)
MAX1576ETG+
-40°C to +85°C
LED Camera Flashes
Cell Phones and Smart Phones
PDAs, Digital Cameras, and Camcorders
+ Denotes lead-free package.
Pin Configuration appears at end of data sheet.
Typical Operating Circuit
1μF
1μF
INPUT
OUTPUT
2.7V TO 5.5V
UP TO 480mA
C1P
C1N
C2P
C2N
INP
IN
OUT
FLASH
MAIN
4.7μF
4.7μF
1μF
GND1
LED1
LED2
LED3
LED4
LED5
MAX1576Y
ENM1
ENM2
ON/OFF AND
CURRENT
SETTING
ENF1
ENF2
LED6
LED7
LED8
SETM
SETF
GND2 PGND
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
ABSOLUTE MAXIMUM RATINGS
INP, IN, OUT, ENM1, ENM2, ENF1,
OUT Short Circuit to GND ..........................................Continuous
ENF2 to GND1 .......................................................-0.3V to +6.0V
SETF, SETM, LED1, LED2, LED3, LED4, LED5,
Continuous Power Dissipation (T = +70°C)
24-Pin Thin QFN (derate 20.8mW/°C
above +70°C)..............................................................1666mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
A
LED6, LED7, LED8 to GND1 ....................-0.3V to (V + 0.3V)
IN
C1N, C2N to GND1 ........................................-0.3V to (V + 1V)
IN
C1P, C2P to
GND1................ -0.3V to Greater of (V
+ 1V) or (V + 1V)
IN
OUT
GND2, PGND to GND1 .........................................-0.3V to +0.3V
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 = 3.6V, V
= V
= V
= 0V, ENM1 = ENM2 = ENF1 = ENF2 = IN, R
= R
= 6.8kΩ, T = -40°C to +85°C,
SETF
A
IN
GND1
GND2
PGND
SETM
unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
CONDITIONS
MIN
2.7
TYP
MAX
5.5
UNITS
IN Operating Voltage
V
V
Undervoltage-Lockout Threshold
Undervoltage-Lockout Hysteresis
Overvoltage Protection Threshold
V
V
rising or falling
2.25
2.45
50
2.60
IN
mV
V
rising
5
OUT
1MHz switching, no load, 1.5x or 2x mode
1x mode 10% setting, LED5–LED8 off
ENM1 = ENM2 = ENF1 = ENF2 = GND
3.8
0.3
0.1
2
6.0
3
Supply Current
mA
Shutdown Supply Current
Soft-Start Time
µA
ms
V
SET_ Bias Voltage
0.604
0.01
SET_ Leakage in Shutdown
SETM Current Range
SETF Current Range
ENM1 = ENM2 = ENF1 = ENF2 = GND, V
= 0V or V
1
µA
µA
µA
SET_
IN
40
40
130
145
SETM to Main LED_ Current Ratio
100% setting, LED1–4
100% setting, LED5–8
233
708
A/A
A/A
(I
/ I
)
LED SETM
SETF to Flash LED_ Current Ratio
(I / I
)
LED SETF
LED1–4
LED5–8
(Note 2)
-6
-8
+6
+8
LED_ Current Accuracy
%
LED_ to LED_ Current Matching
Maximum LED_ Sink Current
LED_ Dropout Voltage
-3.5
27
0.7
30
+3.5
%
LED1–LED4, R
LED5–LED8, R
(Note 3)
= 4.64kΩ
= 4.12kΩ
SETM
SETF
mA
mV
mV
90
100
40
90
LED_ 1.5x and 2x Regulation
Voltage
150
100
150
LED_ 1x to 1.5x or 1.5x to 2x
Mode Transition Threshold
90
110
mV
mV
Input-Voltage-Mode Transition
Hysteresis
2
_______________________________________________________________________________________
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
ELECTRICAL CHARACTERISTICS (continued)
(V = 3.6V, V
= V
= V
= 0V, ENM1 = ENM2 = ENF1 = ENF2 = IN, R
= R
= 6.8kΩ, T = -40°C to +85°C,
SETF
A
IN
GND1
GND2
PGND
SETM
unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
CONDITIONS
ENM1 = ENM2 = ENF1 = ENF2 = GND
MIN
TYP
MAX
UNITS
LED_ Leakage in Shutdown
0.1
2
µA
Charge-Pump Maximum OUT
Current
V
≥ 3.15V, V
= 3.9V
OUT
480
mA
IN
1x mode, (V - V
) / I
OUT
2.5
5.0
5.0
IN
OUT
Open-Loop OUT Resistance
1.5x mode, (1.5V - V
) / I
OUT OUT
Ω
IN
2x mode, (2V - V
) / I
OUT OUT
IN
Switching Frequency
EN_ High Voltage
EN_ Low Voltage
EN_ Input Current
1
MHz
V
V
V
V
= 2.7V to 5.5V
= 2.7V to 5.5V
1.6
IN
0.4
1
V
IN
= 0V or 5.5V
0.01
470
µA
EN_
EN_ Low Shutdown Delay t
(See Figure 3)
SHDN
225
800
µs
EN_ t (See Figure 3)
0.5
0.5
50
250.0
µs
µs
µs
LO
EN_ t (See Figure 3)
HI
Initial EN_ t (See Figure 3)
HI
Only required for first EN_ pulse
OUT Pulldown Resistance in
Shutdown
ENM1 = ENM2 = ENF1 = ENF2 = GND
5
kΩ
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
+160
20
°C
°C
Note 1: Specifications to -40°C are guaranteed by design and not production tested.
Note 2: LED current matching is defined as: (I
- I
) / I
. Matching is for LEDs within the main group (LED1–LED4) or the
LED_ AVG
AVG
flash group (LED5–LED8).
Note 3: Dropout voltage is defined as the LED_ to GND_ voltage at which current into LED_ drops 10% from the value at V
= 0.2V.
LED_
_______________________________________________________________________________________
3
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
Typical Operating Characteristics
(V = 3.6V, EN_ = IN, Circuit of Figure 1, R
IN
= 9.09kΩ, R
= 4.12kΩ, T = +25°C, unless otherwise noted.)
A
SETF
SETM
EFFICIENCY vs. Li+ BATTERY
VOLTAGE DRIVING FOUR MAIN LEDs
100
EFFICIENCY vs. Li+ BATTERY
VOLTAGE DRIVING FLASH LED MODULE
BATTERY CURRENT vs. SUPPLY VOLTAGE
DRIVING FOUR MAIN LEDs
100
90
80
70
60
50
40
120
100
80
60
40
20
0
80mA
TOTAL
160mA
TOTAL
I
= 15mA
V
V
FALLING
RISING
LED
IN
IN
90
15mA/LED
80
4.5mA/LED
70
I
= 4.5mA
LED
1.5mA/LED
60
400mA
TOTAL
I
= 1.5mA
LED
3.6
50
40
4.2 3.9
3.8
3.7
3.6
3.5
3.4 3.0
4.2 3.9
3.8
3.7
3.6
3.5
3.4 3.0
2.7
3.0
3.3
3.9
4.2
Li+ BATTERY VOLTAGE (V, TIME-WEIGHTED)
Li+ BATTERY VOLTAGE (V, TIME-WEIGHTED)
SUPPLY VOLTAGE (V)
INPUT RIPPLE VOLTAGE vs. SUPPLY
VOLTAGE WITH FOUR MAIN LEDs
INPUT RIPPLE VOLTAGE vs. SUPPLY
VOLTAGE WITH FLASH AND MAIN LEDs
BATTERY CURRENT vs. SUPPLY
VOLTAGE DRIVING FLASH
20
18
16
14
12
10
8
20
18
16
14
12
10
8
900
800
700
600
500
400
300
200
100
0
4 MAIN LEDs AT 15mA EACH
I
= 410mA
= 168mA
FLASH
I
= 400mA
FLASH
I
= 160mA
FLASH
I
FLASH
I
= 81mA
FLASH
6
6
I
I
= 4.5mA
= 1.5mA
LED
I
= 80mA
FLASH
LED
4
I
= 15mA
4
LED
2
2
0
0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
2.7
3.0
3.3
3.6
3.9
4.2
SUPPLY VOLTAGE (V)
LED CURRENT MATCHING vs. SUPPLY
VOLTAGE WITH FOUR MAIN LEDs
LED CURRENT vs. AMBIENT
TEMPERATURE WITH FLASH
LED CURRENT vs. AMBIENT
TEMPERATURE WITH FOUR MAIN LEDs
16.5
16.3
16.1
15.9
15.7
15.5
15.3
15.1
14.9
14.7
14.5
165
164
163
162
161
160
62.0
61.9
61.8
61.7
61.6
61.5
61.4
61.3
61.2
61.1
61.0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
-40
-15
10
35
60
85
-40
-15
10
35
60
85
AMBEINT TEMPERATURE (°C)
AMBEINT TEMPERATURE (°C)
4
_______________________________________________________________________________________
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
Typical Operating Characteristics (continued)
(V = 3.6V, EN_ = IN, Circuit of Figure 1, R
= 9.09kΩ, R
= 4.12kΩ, T = +25°C, unless otherwise noted.)
A
SETF
IN
SETM
LED CURRENT vs. R
LED CURRENT vs. R
SETM
SETF
100
10
1
100
10
1
100% BRIGHTNESS SETTING
10
100% BRIGHTNESS SETTING
10
1
100
1
100
R
(kΩ)
R
(kΩ)
SETF
SETM
OPERATING WAVEFORMS (1.5x MODE)
OPERATING WAVEFORMS (1x MODE)
MAX1576 toc13
MAX1576 toc12
V
OUT
50mV/div
AC-COUPLED
V
V
OUT
50mV/div
AC-COUPLED
OUT
V
IN
20mV/div
AC-COUPLED
20mV/div
AC-COUPLED
V
IN
V
IN
4 MAIN LEDs AT 20mA EACH
400ns/div
4 MAIN LEDs AT 20mA EACH
400ns/div
FLASH RESPONSE
OPERATING WAVEFORMS (2x MODE)
MAX1576 toc15
MAX1576 toc14
V
V
5V/div
EN1F
EN2F
V
OUT
V
OUT
50mV/div
AC-COUPLED
500mA/div
500mA/div
I
IN
V
IN
20mV/div
AC-COUPLED
V
IN
I
OUT
OUT
4 MAIN LEDs AT 20mA EACH
FLASH AT 400mA
500mV/div
AC-COUPLED
V
400μs/div
400ns/div
4 MAIN LEDs AT 20mA EACH. 400mA FLASH
_______________________________________________________________________________________
5
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
Typical Operating Characteristics (continued)
(V = 3.6V, EN_ = IN, Circuit of Figure 1, R
= 9.09kΩ, R
= 4.12kΩ, T = +25°C, unless otherwise noted.)
IN
A
SETM
SETF
LINE-TRANSIENT RESPONSE
SINGLE-WIRE DIMMING RESPONSE
MAX1576 toc17
MAX1576 toc16
V
,
5V/div
EN1M
V
EN2M
V
IN
1V/div
3V
1V/div
AC-COUPLED
V
I
OUT
OUT
I
OUT
OUT
50mA/div
2V/div
50mA/div
0
V
40μs/div
2ms/div
Pin Description
PIN
NAME
FUNCTION
Output. Bypass to ground with a 4.7µF ceramic capacitor. Connect to the anodes of all the LEDs. OUT is
internally pulled to ground through a 5kΩ resistor during shutdown.
1
OUT
2
3
ENM1
ENM2
ENF1
ENF2
LED8
LED7
LED6
LED5
GND2
GND1
LED4
LED3
LED2
LED1
Enable and Brightness Control for LED1–LED4 (Backlight). See Table 1 and Figure 3.
Enable and Brightness Control for LED5–LED8 (Flash). See Table 2 and Figure 3.
4
5
6
Flash LED_ Cathode Connection and Charge-Pump Feedback. Current flowing into LED_ is based on the
7
ENF_ logic levels and R . The charge pump regulates the lowest LED_ voltage to 0.15V. Grounding any
SETF
9
LED_ forces OUT to operate at approximately 5V. Connect LED_ to IN if this LED is not populated.
10
8
Ground. Connect GND_ to system ground and the ground side of the input bypass capacitor as close to the
IC as possible.
14
11
12
13
15
Main LED_ Cathode Connection and Charge-Pump Feedback. Current flowing into LED_ is based on the
ENM_ logic levels and R . The charge-pump regulates the lowest LED_ voltage to 0.15V. Grounding any
SETM
LED_ forces OUT to operate at approximately 5V. Connect LED_ to IN if this LED is not populated.
Bias Current Set Input for LED1–LED4. The current flowing out of SETM sets the maximum (100%) bias
current into each LED. SETM is internally biased to 0.604V. Connect a resistor (R
) from SETM to ground
16
17
SETM
SETF
SETM
to set the main LED current, R
= (233 x 0.604) / I
. SETM is high impedance during shutdown.
SETM
LED(MAX)
Bias Current Set Input for LED5–LED8. The current flowing out of SETF sets the maximum (100%) bias
current into each LED. SETF is internally biased to 0.604V. Connect a resistor (R ) from SETF to ground
SETF
to set the flash LED current, R
= (708 x 0.604) / I
. SETF is high impedance during shutdown.
SETF
LED(MAX)
6
_______________________________________________________________________________________
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
Pin Description (continued)
PIN
18
NAME
IN
FUNCTION
Supply Voltage Input. Bypass to ground with a 1µF ceramic capacitor. The input voltage range is 2.7V to
5.5V. IN is high impedance during shutdown.
19
PGND
C1N
Power Ground. Connect PGND to system ground. PGND is used for charge-pump switching currents.
Transfer Capacitor 1 Negative Connection. Connect to a 1µF ceramic capacitor between C1P and C1N.
C1N is internally shorted to IN during shutdown.
20
Transfer Capacitor 2 Negative Connection. Connect to a 1µF ceramic capacitor between C2P and C2N.
C2N is internally shorted to IN during shutdown.
21
22
23
24
—
C2N
INP
C2P
C1P
EP
Supply Voltage Input. Bypass to PGND with a 4.7µF ceramic capacitor. The input voltage range is 2.7V to
5.5V. INP is high impedance during shutdown.
Transfer Capacitor 2 Positive Connection. Connect a 1µF ceramic capacitor from C2P to C2N. During
shutdown, if OUT > IN, C2P is shorted to OUT, and if OUT < IN, C2P is shorted to IN.
Transfer Capacitor 1 Positive Connection. Connect a 1µF ceramic capacitor from C1P to C1N. During
shutdown, if OUT > IN, C1P is shorted to OUT, and if OUT < IN, C1P is shorted to IN.
Exposed Paddle. Connect the exposed paddle to ground. Connect PGND, GND1, and GND2 to the
exposed paddle directly under the IC.
Soft-Start
Detailed Description
The MAX1576 includes soft-start circuitry to limit inrush
current at turn-on. Once the input voltage is applied,
the output capacitor is charged directly from the input
with a ramped current source (with no charge-pump
action) until the output voltage approaches the input
voltage. Once this occurs, the charge pump deter-
mines if 1x, 1.5x, or 2x mode is required. In the case of
1x mode, the soft-start is terminated and normal opera-
tion begins. In the case of 1.5x or 2x mode, soft-start
operates until the lowest of LED1–LED4 reaches regu-
lation. If the output is shorted to ground or is pulled less
than 1.25V, the output current is limited by soft-start.
The MAX1576 charge pump drives up to four white
LEDs in the main display for backlighting and up to four
white LEDs for flash with regulated constant current for
uniform intensity. By utilizing adaptive 1x/1.5x/2x
charge-pump modes and very-low-dropout current reg-
ulators, it achieves high efficiency over the 1-cell lithi-
um-battery input voltage range. 1MHz fixed-frequency
switching allows for tiny external components and low
input ripple.
1x to 1.5x Switchover
When V is higher than V
, the MAX1576 operates
IN
OUT
in 1x mode and V
is pulled up to V . The internal
OUT
IN
True Shutdown™ Mode
When ENM1, ENM2, ENF1, and ENF2 are simultaneously
held low, the MAX1576 is shut down after a 0.5ms shut-
down delay and the input is isolated from the output. OUT
is internally pulled to GND with 5kΩ during shutdown.
current regulators regulate the LED current. As V
IN
drops, V
eventually falls below the switchover
LED_
threshold of 100mV and the MAX1576 starts switching
in 1.5x mode. When the input voltage rises above V
OUT
by approximately 50mV, the MAX1576 switches back to
1x mode.
Thermal Shutdown
The MAX1576 includes a thermal-limit circuit that shuts
down the IC at approximately +160°C. Turn-on occurs
after the IC cools by approximately 20°C.
1.5x to 2x Switchover
When V is less than V
but greater than two-thirds
OUT
IN
V
, the MAX1576 operates in 1.5x mode. The inter-
OUT
nal current regulators regulate the LED current. As V
IN
Applications Information
drops, V
eventually falls below the switchover
LED_
Setting the Main Output Current
SETM controls LED1–LED4 bias current. Current flow-
ing into LED1, LED2, LED3, and LED4 is a multiple of
the current flowing out of SETM.
threshold of 100mV, and the MAX1576 starts switching
in 2x mode. When the input voltage rises above two-
thirds V
by approximately 50mV, the MAX1576
OUT
switches back to 1.5x mode.
True Shutdown is a trademark of Maxim Integrated Products, Inc.
I
= I
= I
= I
= K x (0.604V / R
)
LED1
LED2
LED3
LED4
SETM
_______________________________________________________________________________________
7
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
C3
C4
1μF
1μF
C1P C1N
C2P C2N
INPUT
2.7V TO 5.5V
OUTPUT
UP TO 480mA
INP
IN
OUT
1x/1.5x/2x REGULATING
CHARGE PUMP
C
IN
4.7μF
C
OUT
4.7μF
C2
1μF
MAX1576Y
ERROR
AMP1
OVD
1.25V
PGND
CONTROL AND
REFERENCE
SELMIN
ENM1
ENM2
ENF1
ENF2
0.15V
FLASH CONTROL
MAIN CONTROL
0.604V
LED1
LED2
LED3
LED4
D1
IN
D2
D3
D4
+
+
+
+
ERROR
AMP 2
–
–
–
–
SETM
GND1
R
SETM
IN
LED5
LED6
LED7
LED8
D5
D6
D7
D8
+
+
+
+
–
–
–
–
ERROR
AMP 3
SETF
R
SETF
GND2
Figure 1. Block Diagram and Typical Application Circuit
_______________________________________________________________________________________
8
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
where K = 23, 70, or 233 (depending upon the state of
1μF
1μF
ENM1 and ENM2, see Table 1), and R
is the resis-
SETM
tor connected between SETM and ground (see the
Typical Operating Circuit).
INPUT
2.7V TO 5.5V
OUTPUT
UP TO 480mA
C1P
INP
C1N C2P
C2N
OUT
IN
LUXEON
DS25
4.7μF
Setting the Flash Output Current
SETF controls the LED5–LED8 bias current. Current
flowing into LED5, LED6, LED7, and LED8 is a multiple
of the current flowing out of SETF.
4.7μF
1μF
PGND
GND1
MAX1576
LED1
LED2
LED3
LED4
LED5
ENM1
ENM2
I
= I
= I
= I
= N x (0.604V / R
)
LED5
LED6
LED7
LED8
SETF
ON/OFF AND
CURRENT
SETTING
where N = 142, 283, or 708 (depending upon ENF1
and ENF2, see Table 2), and R is the resistor con-
LED6
LED7
LED8
GND2
SETF
ENF1
ENF2
nected between SETF and ground (see the Typical
Operating Circuit).
SETM
SETF
Single-Wire Pulse Dimming
For more dimming flexibility or to reduce the number of
control traces, the MAX1576 supports serial pulse dim-
ming. Connect ENM1 and ENM2 (or ENF1 and ENF2)
together to enable single-wire pulse dimming of the
main (or flash) LEDs. When ENM1 and ENM2 (or ENF1
and ENF2) go high simultaneously, the main (or flash)
LEDs are enabled at full brightness. Each subsequent
low-going pulse (500ns to 250µs pulse width) reduces
the LED current by 10%, so after one pulse the LED
Figure 2. Typical Application Circuit for Driving a Single High-
Brightness LED
Table 1. ENM1/ENM2 States
LED1–LED4
CURRENT
ENM1/ENM2 STATES
BRIGHTNESS
ENM1 = low, ENM2 = low
ENM1 = low, ENM2 = high
ENM1 = high, ENM2 = low
ENM1 = high, ENM2 = high
Shutdown
0
1/10 Brightness
3/10 Brightness
Full Brightness
23 x I
70 x I
SETM
SETM
current is 0.9 x I
. The 10th pulse reduces the cur-
LED_
rent by 5% so the LED current reduces from 0.1 x I
LED_
233 x I
to 0.05 x I
. The 11th pulse sets the LED current
SETM
LED_
back to I
. Figure 3 shows a timing diagram for sin-
LED_
gle-wire pulse dimming. Because soft-start is longer
Table 2. ENF1/ENF2 States
than the initial t , apply dimming pulses quickly upon
HI
startup (after initial t ) to avoid LED_ current transition-
HI
LED5–LED8
CURRENT
ENF1/ENF2 STATES
BRIGHTNESS
ing through full brightness.
ENF1 = low, ENF2 = low
ENF1 = low, ENF2 = high
ENF1 = high, ENF2 = low
ENF1 = high, ENF2 = high
Shutdown
0
Simple On/Off Control
If dimming control is not required, connect ENM1 to
ENM2 (or ENF1 to ENF2) for simple on/off control. In
1/5 Brightness
2/5 Brightness
Full Brightness
142 x I
283 x I
708 x I
SETM
SETM
SETM
this case, LED current is set by the values of R
SETM
(or R
).
SETF
INITIAL t
HI
≥ 50μs
0
1
2
3
9
10
11
4
5
6
7
8
ENM1 AND ENM2
OR ENF1 AND ENF2
t
SOFT-START
100%
t
HI
t
SHDN
t
LO
0.5ms (typ)
≥ 500ns
500ns TO 250μs
100%
90%
90%
80%
70%
60%
50%
40%
I
30%
LED_
20%
10%
5%
SHDN
SHDN
Figure 3. EN_ Timing Diagram
_______________________________________________________________________________________
9
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
1μF
1μF
INPUT
2.7V TO 5.5V
OUTPUT
UP TO 480mA
C1P
INP
C1N
C2P
C2N
OUT
FLASH
MAIN
IN
4.7μF
4.7μF
1μF
GND1
LED1
MAX1576
LED2
LED3
LED4
LED5
ON
ENM2
ENM1
OFF
PWM INPUT
LED6
ON/OFF AND
CURRENT
SETTING
LED7
LED8
ENF1
ENF2
SETM
SETF
GND2 PGND
Figure 4. Dimming Using PWM Signal into ENM1
1μF
1μF
INPUT
2.7V TO 5.5V
OUTPUT
UP TO 480mA
C1P
INP
C1N
C2P
C2N
OUT
FLASH
MAIN
IN
4.7μF
4.7μF
1μF
GND1
LED1
MAX1576
LED2
LED3
LED4
LED5
ENM2
ENM1
ON/OFF AND
CURRENT
SETTING
ENF1
ENF2
LED6
LED7
LED8
R1
14.3kΩ
R2
14.3kΩ
SETM
SETF
GND2 PGND
PWM INPUT
0 TO 2.5V
C6
1μF
R
SETM
9.09kΩ
Figure 5. Dimming Using Filtered PWM Signal
Dimming Using PWM into ENM1
Use ENM2 for shutdown and drive ENM1 with a PWM
signal. LED brightness can be varied from 1/10 to full
brightness based on the duty cycle of the PWM signal.
The waveforms in the Typical Operating Characteristics
show the response time of dimming. Drive ENM2 high
to keep the IC on, eliminating any soft-start delay that
would impede PWM control and allowing a PWM fre-
quency up to 5kHz (Figure 4).
Dimming Using a DAC or Filtered PWM
Both the main LEDs and flash LEDs allow dimming
using a DAC or filtered PWM. Use a DAC output to sum
a current into the SET_ node, or use a high-frequency
PWM signal to drive an RCR filter on SET_ (Figure 5).
With the component values shown in Figure 5, a 0%
PWM duty cycle corresponds to 20mA/LED, while a
100% PWM duty cycle corresponds to 0mA/LED. At
PWM frequencies above 5kHz, C6 may be reduced.
10 ______________________________________________________________________________________
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
1μF
1μF
INPUT
2.7V TO 5.5V
OUTPUT
UP TO 480mA
C1P
INP
C1N
C2P
C2N
OUT
FLASH
MAIN
IN
4.7μF
4.7μF
1μF
GND1
LED1
MAX1576
LED2
LED3
LED4
LED5
ENM1
ENM2
ON/OFF AND
CURRENT
SETTING
LED6
ENF1
ENF2
LED7
LED8
SETM
SETF
GND2 PGND
Figure 6. Providing Increased LED Current per LED
1μF
1μF
INPUT
2.7V TO 5.5V
OUTPUT
UP TO 260mA
C1P
INP
C1N
C2P
C2N
OUT
FLASH
MAIN
IN
4.7μF
4.7μF
1μF
GND1
LED1
IN
MAX1576
LED2
LED3
LED4
LED5
ENM1
ENM2
ON/OFF AND
CURRENT
SETTING
IN
LED6
ENF1
ENF2
LED7
LED8
SETM
SETF
GND2 PGND
Figure 7. Schematic for when Fewer than 8 LEDs is Acceptable
through each LED but ensures that the unused LED_ is
properly terminated.
Driving Fewer than 8 LEDs
When driving fewer than 8 LEDs, two different connec-
tion schemes can be used. The first scheme is shown
in Figures 2 and 6, where LED_ is connected to the
adjacent LED_. This method allows increased current
through the LED and effectively allows total LED current
Input Ripple
For LED drivers, input ripple is more important than out-
put ripple. Input ripple is highly dependent on the
source supply’s impedance. Adding a lowpass filter to
the input further reduces input ripple. Alternately,
increasing C to 10µF cuts input ripple in half with only
IN
a small increase in footprint. The 1x mode always has
very low input ripple.
to be I
multiplied by the number of pins connected.
LED
The second method of connection is shown in Figure 7,
where standard white LEDs are used and fewer than 8
are connected. This scheme does not alter current
______________________________________________________________________________________ 11
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
Table 3. Recommended Components
DESIGNATION
VALUE
4.7µF
1µF
MANUFACTURER
PART NUMBER
DESCRIPTION
C
, C
IN OUT
Murata
GRM188R60J475K 4.7µF 10%, 6.3V X5R ceramic capacitors (0603)
GRM155R60J105K 1µF 10%, 6.3V X5R ceramic capacitors (0402)
C2, C3, C4
D1–D4
Murata
—
Nichia
NSCW215T
NBCW011T
—
White LEDs
D5 (D5–D8)
—
Nichia
White LEDs, four LEDs in one package
1% resistors
R
, R
As required
Kamaya
SETM SETF
Typical operating waveforms shown in the Typical
Operating Characteristics show input ripple in 1x, 1.5x,
and 2x mode.
Pin Configuration
Component Selection
Use only ceramic capacitors with an X5R, X7R, or better
dielectric. See Table 3 for a list of recommended parts.
18 17 16 15 14 13
12 LED3
11 LED4
10 LED5
PGND 19
C1N 20
C2N 21
INP 22
PC Board Layout and Routing
The MAX1576 is a high-frequency switched-capacitor
voltage regulator. For best circuit performance, use a
MAX1576Y
9
8
7
LED6
GND2
LED7
solid ground plane and place C , C
, C2, C3, and
OUT
IN
C4 as close to the MAX1576 as possible. There should
C2P 23
C1P 24
be no vias on C . Connect GND1, GND2, and PGND
IN
+
to the exposed paddle directly under the IC. Refer to
the MAX1576 evaluation kit for an example.
1
2
3
4
5
6
Chip Information
TRANSISTOR COUNT: 6679
THIN QFN
4mm x 4mm
PROCESS: BiCMOS
12 ______________________________________________________________________________________
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
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.)
PACKAGE OUTLINE,
12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm
1
E
21-0139
2
______________________________________________________________________________________ 13
480mA White LED 1x/1.5x/2x Charge Pump for
Backlighting and Camera Flash
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.)
PACKAGE OUTLINE,
12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm
2
E
21-0139
2
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.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
EN GL ISH • ? ? ? ? • ? ? ? • ? ? ?
BU Y C OM PA N Y M EM B ER S
W HA T ' S N EW PR ODUCTS S OLU TI ONS D E SI G N AP P NOT ES SUPP ORT
MA X1 576
Pa r t Nu mb e r T ab l e
N o te s:
1 . S ee t he M A X 1 5 7 6 Q u ic k V ie w D a ta Sh e e t f or f urt her inf orm ati on o n th is p rodu ct fam i l y or d ow n lo a d th e M AX15 76
f ul l d at a s h ee t (P DF, 3 08 k B) .
2. O th er o p ti on s a n d l inks f or p urch asi ng p arts a re l is te d at : h t tp : / /w w w. m a xi m -i c. com /s al es .
3 . Did n' t F ind W ha t You N e ed ? A sk our ap pli cat ion s e ng ine ers . Exp ert a ssi stance i n findi ng part s, us uall y wi thi n one
b us i ne ss d a y.
4 . Pa r t n u mb e r suf f ix e s : T o r T &R = ta p e a n d r e e l; + = Ro HS/le ad - fr e e ; # = RoH S/ lea d - e xe m p t. Mo r e : S e e fu ll da t a sh e et
o r P a rt N a mi n g C o nv en t i o n s .
5 . * S ome p ackages hav e variations, listed on the drawing. " PkgCode/Variation" te ll s w hi ch vari at i on th e pro d uct u se s.
P art Num ber
F r ee
Sa mp le
B uy
D i re c t
T em p
R oHS/L ead- Fr ee?
Ma t e ri a l s A n a ly s is
P a c ka g e : TY PE P INS S IZE
D R A WI N G C O D E / V A R *
MA X 1 5 7 6 E T G + G 1 0 4
- 4 0 C t o + 8 5 C Ro H S / Le a d -F re e: Yes
M AX 15 7 6E TG -T
MA X1 57 6E TG
THIN QFN ;24 pin ;4X4X0.8m m
Dwg : 21 -0 13 9E (P D F )
U s e p k g c o d e / va r i a t i o n: T 2 4 4 4 -4 *
- 4 0 C t o + 8 5 C Ro H S / Le a d -F re e: N o
Ma t e ri a l s A n a ly s is
THIN QFN ;24 pin ;4X4X0.8m m
Dwg : 21 -0 13 9E (P D F )
- 4 0 C t o + 8 5 C Ro H S / Le a d -F re e: N o
Ma t e ri a l s A n a ly s is
U s e p k g c o d e / va r i a t i o n: T 2 4 4 4 -4 *
M AX1 57 6E TG+
MA X15 76E TG+ T
THIN QFN ;24 pin ;4X4X0.8m m
Dwg : 21 -0 13 9E (P D F )
U se p kg c o de / va r i at i o n : T2 4 4 4 +4 *
- 4 0 C t o + 8 5 C Ro H S / Le a d -F re e: Yes
Ma t e ri a l s A n a ly s is
THIN QFN ;24 pin ;4X4X0.8m m
Dwg : 21 -0 13 9E (P D F )
- 4 0 C t o + 8 5 C Ro H S / Le a d -F re e: Yes
Ma t e ri a l s A n a ly s is
U se p kg c o de / va r i at i o n : T2 4 4 4 +4 *
Did n' t F ind W ha t You Ne e d ?
CO NT ACT U S: SE ND US AN EMAI L
Co p y rig h t 2 00 7 b y M a x im I n te g r a te d Pr o d u c ts , D a lla s S em i co n d u c to r • Le ga l N ot i ce s • P ri va c y P o l ic y
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