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19-3688; Rev 2; 5/06
KIT ATION EVALU ABLE AVAIL
1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN
General Description Features
Powers Up to 8 LEDs Up to 30mA/LED Drive for Backlight Up to 400mA Total Drive for Flash Two Internal Low-Noise 200mA LDOs 94% Max/85% Avg Efficiency (PLED/PBATT) over Li+ Battery Discharge 0.2% Typical LED Current Matching Adaptive 1x/1.5x/2x Mode Switchover Flexible Brightness Control Single-Wire Serial Pulse Interface (32 Steps) 2-Bit Logic (Three Levels) Thermal TA Derating Function Low Input Ripple and EMI 2.7V to 5.5V Supply Voltage Range Soft-Start, Overvoltage, and Thermal-Shutdown Protection 28-Pin Thin QFN, 4mm x 4mm Package
MAX8631X/Y
The MAX8631X/Y charge pump drives up to eight white LEDs with regulated constant current for uniform intensity. The main group of LEDs (M1-M4) can be driven up to 30mA per LED for backlighting. The flash group of LEDs (F1-F4) is independently controlled and can be driven up to 100mA per LED (or 400mA total). Two 200mA LDOs are on-board to provide power for camera functions. The LDOs' output voltages are pin-programmable to meet different camera-module requirements. By utilizing adaptive 1x/1.5x/2x chargepump modes and very-low-dropout current regulators, the MAX8631X/Y achieves high efficiency over the full 1-cell lithium-battery voltage range. The 1MHz fixed-frequency switching allows for tiny external components, and the regulation scheme is optimized to ensure low EMI and low input ripple. The MAX8631X/Y is available in a 28-pin thin QFN, 4mm x 4mm lead-free package (0.8mm max height).
Applications
Camera Phones and Smartphones Backlighting and Flash PDAs, Digital Cameras, and Camcorders
Typical Operating Circuit
1F INPUT 2.7V TO 5.5V 1F OUTPUT UP TO 480mA 10F MAX8631X/Y M1 M2 M3 M4 F1 F2 F3 F4 LDO1 LDO2 1F SETM SETF REF 0.01F 1F CAMERA MODULE MAIN FLASH
Ordering Information
PART TEMP RANGE -40C to +85C -40C to +85C PIN-PACKAGE 28 Thin QFN-EP* 4mm x 4mm (T2844-1) 28 Thin QFN-EP* 4mm x 4mm (T2844-1)
C1P PIN IN
C1N
C2P
C2N OUT
MAX8631XETI+ MAX8631YETI+
10F GND PGND
*EP = Exposed paddle. +Denotes lead-free package.
MAIN ON/OFF AND DIMMING FLASH ON/OFF DUAL-LDO ON/OFF DUAL-LDO VOLTAGE SELECTION
ENM1 ENM2 ENF ENLDO P1 P2
Pin Configuration appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN MAX8631X/Y
ABSOLUTE MAXIMUM RATINGS
PIN, IN, OUT, REFBP to GND................................-0.3V to +6.0V SETF, SETM, ENLDO, ENM1, ENM2, ENF, P1, P2, LDO1, LDO2 to GND....................-0.3V to (VIN + 0.3V) M1, M2, M3, M4, F1, F2, F3, F4 to GND...-0.3V to (VOUT + 0.3V) C1N, C2N to GND ......................................... -0.3V to (VIN + 1V) C1P, C2P to GND.............. -0.3V to greater of (VOUT + 1V) or (VIN + 1V) PGND to GND .......................................................-0.3V to +0.3V OUT, LDO1, LDO2 Short-Circuit to GND ...................Continuous Continuous Power Dissipation (TA = +70C) 28-Pin Thin QFN 4mm X 4mm (derate 20.8mW/C above +70C) .............................1666mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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
(VIN = 3.6V, VGND = VPGND = 0V, ENM1 = ENM2 = ENF = IN, RSETM = RSETF = 6.8k, P1 = P2 = unconnected, CREF = 0.01F, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER IN Operating Voltage Undervoltage-Lockout Threshold Undervoltage-Lockout Hysteresis 1MHz switching, no load, 1.5x or 2x mode Supply Current 1x mode 10% setting, ENF = GND, VENLDO = VIN, ILDO1 = ILDO2 = 0A ENM1 = ENM2 = ENF = GND, VENLDO = VIN, ILDO1 = ILDO2 = 0A Shutdown Supply Current EN_ High Voltage EN_ Low Voltage EN_ Input Current ENM_ or ENF Low Shutdown Delay tSHDN ENM_ or ENF tLO ENM_ or ENF tHI Initial ENM_ or ENF tHI P1, P2 Shutdown Input Current P1, P2 Input Impedance Thermal-Shutdown Threshold Thermal-Shutdown Hysteresis CHARGE PUMP Overvoltage-Protection Threshold Soft-Start Time VOUT rising 5 2 V ms Temperature rising ENM1 = ENM2 = ENF = ENLDO = GND VIN = 2.7V to 5.5V VIN = 2.7V to 5.5V VEN_ = 0V or 5.5V See Figure 2 See Figure 2 See Figure 2 Only required for first ENM_ or ENF pulse, see Figure 2 TA = +25C TA = +85C 1.5 0.5 0.5 200 1 150 +160 20 0.01 0.1 2 2.5 250.0 TA = +25C TA = +85C 1.4 0.4 1 VIN rising or falling CONDITIONS MIN 2.7 2.25 2.45 130 4.0 0.4 110 0.01 0.1 5 5.5 mA TYP MAX 5.5 2.60 UNITS V V mV
A A V V A ms s s s A k C C
2
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.6V, VGND = VPGND = 0V, ENM1 = ENM2 = ENF = IN, RSETM = RSETF = 6.8k, P1 = P2 = unconnected, CREF = 0.01F, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER 1x to 1.5x or 1.5x to 2x Mode Transition Threshold Input Voltage-Mode Transition Hysteresis Charge-Pump Maximum OUT Current Open-Loop OUT Resistance Charge-Pump Short-Circuit Current Switching Frequency OUT Pulldown Resistance in Shutdown LED DRIVER SET_ Bias Voltage SET_ Leakage in Shutdown SET_ Current Range SETM-to-Main LED Current Ratio (IM_/ISETM) SETF-to-Flash LED Current Ratio (IF_/ISETF) M_, F_ Current Accuracy Maximum Main LED Sink Current Maximum Flash LED Sink Current Current-Derating-Function Start Temperature Current-Derating-Function Slope Dropout Voltage 1.5x and 2x Regulation Voltage M_, F_ Leakage in Shutdown LDO_ Output Voltage Accuracy Output Current Range Current Limit Soft-Start Current Limit VLDO_ = 0V ENM_ = ENF = GND TA = +25C TA = +85C -1.7 0 280 475 160 TA = +40C to +85C (Note 2) 100% setting, M1-M4 100% setting, F1-F4 TA = +25C TA = -40C to current derating start temperature RSETM = 4.6k, for each M_ RSETF = 4.12k, IF1 + IF2 + IF3 + IF4 -1.25 -4 30 400 +40 -1.7 40 150 0.01 0.1 0 +1.7 200 750 1 90 TA = +25C ENM_ = ENF = GND TA = +25C TA = +85C 10 230 690 +1.25 +4 0.6 0.01 0.1 145 1 V A A A/A A/A % mA mA C %/C mV mV A VIN 3.15V, VOUT = 3.9V 1x mode, (VIN - VOUT) / IOUT 1.5x mode, (1.5VIN - VOUT) / IOUT 2x mode, (2VIN - VOUT) / IOUT VOUT < 1.25V 580 0.3 1.1 1.5 500 1 ENM_ = ENF = GND 5 1.0 4.0 4.14 mA MHz k CONDITIONS MIN 90 TYP 100 150 MAX 110 UNITS mV mV mA
MAX8631X/Y
ILDO_ = 150mA, relative to VOUT(NOM) (Note 3)
% mA mA mA
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN MAX8631X/Y
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.6V, VGND = VPGND = 0V, ENM1 = ENM2 = ENF = IN, RSETM = RSETF = 6.8k, P1 = P2 = unconnected, CREF = 0.01F, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Soft-Start Done Time Dropout Voltage Load Regulation Power-Supply Rejection VOUT/VIN Output Noise Voltage (RMS) ILDO_ = 200mA (Note 4) VIN = 3.7V, 100A < ILDO_ < 200mA 10Hz to 10kHz, CLDO_ = 1F, ILDO_ = 10A 10Hz to 100kHz, CLDO_ = 1F, ILDO_ = 10mA -60 40 CONDITIONS MIN TYP 100 120 320 1.3 MAX UNITS s mV % dB VRMS
Note 1: All devices are 100% production tested at TA = +25C. Limits over the operating temperature range are guaranteed by design. Note 2: LED dropout voltage is defined as the M_ or F_ to GND voltage at which current into M_ or F_ drops 10% from the value at M_ or F_ = 0.2V. Note 3: (Greater of 2.7V or (VLDO_ + 0.5V)) VIN 5.5V. Note 4: LDO dropout voltage is defined as VIN - VOUT when VOUT is 100mV below the value of VOUT measured when VIN = VOUT(NOM) + 1V. Since the minimum input voltage is 2.7V, this specification is only meaningful when VOUT(NOM) > 2.5V.
Typical Operating Characteristics
(VIN = VEN_ = 3.6V, circuit of Figure 1, TA = +25C, unless otherwise noted.)
EFFICIENCY vs. Li+ BATTERY VOLTAGE DRIVING FOUR MAIN LEDs
MAX8631X toc01
EFFICIENCY vs. Li+ BATTERY VOLTAGE DRIVING FLASH LED MODULE
MAX8631 toc02
BATTERY CURRENT vs. SUPPLY VOLTAGE DRIVING FOUR MAIN LEDs
ILED = 15mA 100 BATTERY CURRENT (mA) 80 60 ILED = 4.5mA 40 20 0 ILED = 1.5mA VIN FALLING VIN RISING
MAX8631X toc03
100 90 EFFICIENCY PLED/PBATT (%) 80 70 15mA/LED 60 50 40 2.7 3.0 3.3 3.6 3.9 4.5mA/LED 1.5mA/LED
100 80mA TOTAL 90 EFFICIENCY PLED/PBATT (%) 80 70 60 50 40 400mA TOTAL 160mA TOTAL
120
4.2
2.7
3.0
3.3
3.6
3.9
4.2
2.7
3.0
3.3
3.6
3.9
4.2
Li+ BATTERY VOLTAGE (V)
Li+ BATTERY VOLTAGE (V)
SUPPLY VOLTAGE (V)
4
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN
Typical Operating Characteristics (continued)
(VIN = VEN_ = 3.6V, circuit of Figure 1, TA = +25C, unless otherwise noted.)
BATTERY CURRENT vs. SUPPLY VOLTAGE DRIVING FLASH
MAX8631X toc04
MAX8631X/Y
LDO GROUND PIN SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX8631X toc05
INPUT RIPPLE VOLTAGE vs. SUPPLY VOLTAGE WITH FOUR MAIN LEDs
MAX8631X toc06
900 800 BATTERY CURRENT (mA) 700 600 500 400 300 200 100 0 2.7 3.0 3.3 3.6 3.9 IFLASH = 160mA IFLASH = 80mA IFLASH = 400mA
160 GROUND PIN SUPPLY CURRENT (A) 150 140 130 120 110 100 90 80 2.7 3.1 3.5 3.9 4.3 4.7 5.1 NO LOAD, BOTH LDOs 150mA, BOTH LDOs VENM = VENF = 0V, VENLDO = VIN
1.2 1.0 INPUT RIPPLE (mVRMS) 0.8 0.6 ILED = 4.5mA 0.4 ILED = 1.5mA 0.2 0 ILED = 15mA
4.2
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
INPUT RIPPLE VOLTAGE vs. SUPPLY VOLTAGE WITH FLASH AND MAIN LEDs
MAX8631X toc07
LED CURRENT MATCHING vs. SUPPLY VOLTAGE WITH FOUR MAIN LEDs
15.8 MAIN LED CURRENT (mA) 15.6 15.4 15.2 15.0 14.8 14.6 14.4 14.2 14.0
MAX8631X toc08
LED CURRENT MATCHING vs. SUPPLY VOLTAGE WITH FOUR FLASH LEDs
101.5 FLASH LED CURRENT (mA) 101.0 100.5 100.0 99.5 99.0 98.5 98.0
MAX8631X toc09
10 9 8 INPUT RIPPLE (mVRMS) 7 6 5 4 3 2 1 0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 FOUR MAIN LEDs AT 15mA EACH IFLASH = 10mA IFLASH = 40mA IFLASH = 100mA
16.0
102.0
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
LED CURRENT vs. AMBIENT TEMPERATURE WITH FOUR MAIN LEDs
MAX8631X toc10
LED CURRENT vs. AMBIENT TEMPERATURE WITH FLASH
MAX8631X toc11
INDIVIDUAL MAIN LED CURRENT vs. RSETM
MAX8631X toc12
70 60 TOTAL LED CURRENT (mA) 50 40 30 20 10 0 -40 -15 10 35 60
450 400 TOTAL LED CURRENT (mA) 350 300 250 200 150 100 50 0
100
MAIN LED CURRENT (mA) -40 -15 10 35 60 85
10
1 1 10 RSETM (k) 100 AMBIENT TEMPERATURE (C)
85
AMBIENT TEMPERATURE (C)
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN MAX8631X/Y
Typical Operating Characteristics (continued)
(VIN = VEN_ = 3.6V, Circuit of Figure 1, TA = +25C, unless otherwise noted.)
INDIVIDUAL FLASH LED CURRENT vs. RSETF
MAX8631X toc13
OPERATING WAVEFORMS (1x MODE)
MAX8631X toc14
1000
VOUT
50mV/div AC-COUPLED
FLASH LED CURRENT (mA)
100 VIN 10 IIN 4 MAIN LEDS AT 20mA EACH 1 1 10 RSETF (k) 100 400ns/div 2mA/div AC-COUPLED 20mV/div AC-COUPLED
OPERATING WAVEFORMS (1.5x MODE)
MAX8631X toc15
OPERATING WAVEFORMS (2x MODE)
MAX8631X toc16
VOUT
50mV/div AC-COUPLED
VOUT
50mV/div AC-COUPLED
VIN
20mV/div AC-COUPLED
VIN 4 MAIN LEDS AT 20mA EACH, FLASH AT 400mA TOTAL
20mV/div AC-COUPLED
IIN 4 MAIN LEDS AT 20mA EACH 400ns/div
2mA/div AC-COUPLED
IIN
2mA/div AC-COUPLED
400ns/div
STARTUP AND SHUTDOWN MAIN LED RESPONSE
MAX8631X toc17
STARTUP AND SHUTDOWN FLASH LED RESPONSE
MAX8631X toc18
VENM_ 4 MAIN LEDS AT 20mA EACH
5V/div 0V
VENF 4 MAIN LEDS AT 20mA EACH, 400mA TOTAL FLASH
5V/div 0V
100mA/div IOUT 0A IIN
500mA/div 0A 500mA/div IOUT 0A 5V/div 0V 1ms/div
VOUT
5V/div 0V VOUT 1ms/div
6
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN
Typical Operating Characteristics (continued)
(VIN = VEN_ = 3.6V, circuit of Figure 1, TA = +25C, unless otherwise noted.)
LDO DROPOUT VOLTAGE vs. OUTPUT CURRENT
MAX8631X toc20
MAX8631X/Y
SINGLE-WIRE DIMMING RESPONSE
MAX8631X toc19
140 5V/div 0V 500mA/div 120 DROPOUT VOTLAGE (mV) 100 80 60 40 20 0 0 50 100 150
VENM1, VENM2
IOUT
0A
VOUT 2V/div 0V 10ms/div
200
OUTPUT CURRENT (mA)
LDO OUTPUT VOLTAGE ACCURACY vs. OUTPUT CURRENT
XMAX8631X toc21
LOAD-TRANSIENT RESPONSE
MAX8631X toc22
1.0 0.8 OUTPUT VOLTAGE ACCURACY (%) 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 0 50 100 150
VLDO_ = 2.6V VLDO_ 50mV/div AC-COUPLED
100mA
ILDO_ 1mA 200
10s/div
OUTPUT CURRENT (mA)
LOAD-TRANSIENT RESPONSE NEAR DROPOUT
MAX8631X toc23
VIN - VOUT = 77mV, VLDO_ = 2.6V VLDO_ 50mV/div AC-COUPLED
100mA ILDO_ 1mA
10s/div
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN MAX8631X/Y
C3 1F C4 1F
INPUT 2.7V TO 5.5V C1 10F
C1P PIN IN GND
C1N
C2P
C2N LOWDROPOUT LINEAR REGULATORS
LDO1 LDO2 C7 1F OUTPUT UP TO 480mA C5 10F C6 1F
1x/1.5x/2x REGULATING CHARGE PUMP
PGND ERROR AMP 1 OVD 1.25V REFBP C8 0.01F ENM1 ENM2 ENF ENLDO CONTROL AND REFERENCE 0.15V FLASH CONTROL MAIN CONTROL 0.6V P1 P2 IN + - + - + - + - M4 M2 M3 OUT
SELMIN
M1
D1 D2 D3 D4
ERROR AMP 2 SETM RSETM 6.81k IN
GND F1 F2 F3 F4 D5 D6 D7 D8
+ - ERROR AMP 3 SETF RSETF 4.12k
+ -
+ -
+ -
MAX8631X MAX8631Y GND
Figure 1. Functional Diagram and Application Circuit
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN
Pin Description
PIN 1 2 3 4 5 6 7 NAME PIN IN GND LDO1 LDO2 REFBP SETF FUNCTION Supply Voltage Input. Bypass to PGND with a 10F ceramic capacitor. The input voltage range is 2.7V to 5.5V. PIN is high impedance during shutdown. Chip Supply Voltage Input. Bypass to GND with a 10F ceramic capacitor as close to the IC as possible. The input voltage range is 2.7V to 5.5V. IN is high impedance during shutdown. Ground. Connect GND to system ground and the input bypass capacitor as close to the IC as possible. LDO1 Output. Bypass with a 1F ceramic capacitor to GND. LDO1 is pulled to ground through an internal 400k during shutdown. LDO2 Output. Bypass with a 1F ceramic capacitor to GND. LDO2 is pulled to ground through an internal 400k during shutdown. Reference Filter. Bypass REFBP with a 0.01F ceramic capacitor to GND. Bias Current Set Input for F1-F4. The current flowing out of SETF sets the maximum (100%) bias current into each LED. VSETF is internally biased to 0.6V. Connect a resistor (RSETF) from SETF to GND to set the flash current. RSETF = 414 / ILED(MAX). SETF is high impedance during shutdown. Bias Current Set Input for M1-M4. The current flowing out of SETM sets the maximum (100%) bias current into each LED. VSETM is internally biased to 0.6V. Connect a resistor (RSETM) from SETM to GND to set the main LED current. RSETM = 138 / ILED(MAX). SETM is high impedance during shutdown. 400mA Combined Current Flash LED Cathode Connection and Charge-Pump Feedback. Current flowing into F_ is based on ISETF . The charge pump regulates the lowest F_ voltage to 0.15V. Grounding any F_ input forces OUT to operate at approximately 5V. Connect F_ to OUT if this LED is not populated. 30mA Main LED Cathode Connection and Charge-Pump Feedback. Current flowing into M_ is based on the EN_ configuration and ISETM. The charge pump regulates the lowest M_ input voltage to 0.15V. Grounding any M_ forces OUT to operate at approximately 5V. Connect M_ to OUT if this LED is not populated. Default Output-Voltage Select Input. P1 and P2 set the LDO1 and LDO2 voltages to one of nine combinations (Table 2). P2 is high impedance in an off condition and shortly after an on condition. LDO Output Enable. Drive to a logic-level high to turn on both LDOs. Drive to a logic-level low to turn off both LDOs. Enable and Dimming Control for M1-M4. Drive both ENM1 and ENM2 to a logic-level high to turn on the main LEDs. Drive both ENM1 and ENM2 to a logic-level low to turn off the main LEDs. Alternate dimming techniques are discussed in the Applications Information section. Enable and Dimming Control for M1-M4. Drive both ENM1 and ENM2 to a logic-level high to turn on the main LEDs. Drive both ENM1 and ENM2 to a logic-level low to turn off the main LEDs. Alternate dimming techniques are discussed in the Applications Information section. Enable and Dimming Control for F1-F4. Drive ENF to a logic-level high to turn on the flash LEDs. Drive ENF to a logic-level low to turn off the flash LEDs. Dimming techniques are discussed in the Applications Information section. Transfer Capacitor 1 Negative Connection. Connect a 1F ceramic capacitor between C1P and C1N. C1N is internally shorted to IN during shutdown.
MAX8631X/Y
8
SETM
9-12
F4-F1
13-16
M4-M1
17 18
P2 ENLDO
19
ENM2
20
ENM1
21
ENF
22
C1N
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN MAX8631X/Y
Pin Description (continued)
PIN 23 24 25 26 27 28 -- NAME C1P PGND OUT C2P C2N P1 EP FUNCTION Transfer Capacitor 1 Positive Connection. Connect a 1F ceramic capacitor between C1P to C1N. During shutdown, if OUT > IN, C1P is shorted to OUT. If OUT < IN, C1P is shorted to IN. Power Ground. Connect PGND to system ground. PGND is used for charge-pump switching currents. Charge-Pump Output. Bypass OUT to GND with a 10F ceramic capacitor. Connect to the anodes of all the LEDs. OUT is internally pulled to ground through a 5k resistor during shutdown. Transfer Capacitor 2 Positive Connection. Connect a 1F ceramic capacitor between C2P to C2N. During shutdown, if OUT > IN, C2P is shorted to OUT. If OUT < IN, C2P is shorted to IN. Transfer Capacitor 2 Negative Connection. Connect a 1F ceramic capacitor between C2P and C2N. C2N is internally shorted to IN during shutdown. Default Output-Voltage Select Input. P1 and P2 set the LDO1 and LDO2 voltages to one of nine combinations (Table 2). P1 is high impedance in an off condition and shortly after an on condition. Exposed Paddle. Connect to GND and PGND.
Detailed Description
The MAX8631X/Y charge pump drives up to 4 white LEDs in the main display for backlighting and up to 4 white LEDs for flash, all with regulated constant current for uniform intensity. By utilizing adaptive 1x/1.5x/2x charge-pump modes and very-low-dropout current regulators, it achieves high efficiency over the 1-cell lithium-battery input voltage range. 1MHz fixed-frequency switching allows for tiny external components and low input ripple. Two on-board 200mA programmable-output-voltage LDOs are provided to meet camera-module requirements.
Soft-Start
The MAX8631X/Y 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 chargepump action) until the output voltage approaches the input voltage. Once the output capacitor is charged, the charge pump determines if 1x, 1.5x, or 2x mode is required. In the case of 1x mode, the soft-start is terminated and normal operation begins. In the case of 1.5x or 2x mode, soft-start operates until the lowest voltage of M1-M4 and F1-F4 reaches regulation. If the output is shorted to ground or is pulled to less than 1.25V, the output current is limited by soft-start.
1x to 1.5x Switchover
When VIN is higher than VOUT, the MAX8631X/Y operates in 1x mode and VOUT is pulled up to VIN. The internal current regulators regulate the LED current. As V IN drops, V M_ (or V F_ ) eventually falls below the switchover threshold of 100mV and the MAX8631X/Y starts switching in 1.5x mode. When the input voltage rises above V OUT by approximately 50mV, the MAX8631X/Y switches back to 1x mode.
True ShutdownTM Mode
When ENM1, ENM2, and ENF are simultaneously held low for 2ms or longer, the MAX8631X/Y is shut down and put in a low-current shutdown mode, and the input is isolated from the output. OUT is internally pulled to GND with 5k during shutdown.
Thermal Derating
The MAX8631X/Y limits the maximum LED current depending on the die temperature. The maximum LED current is set by the RSETM and RSETF resistors. Once the temperature reaches +43C, the LED current decreases by 1.7%/C. Due to the package's exposed paddle, the die temperature is always very close to the PC board temperature. The temperature derating function allows the LED current to be safely set higher at normal operating temperatures, thereby allowing either a brighter display or fewer LEDs to be used for normal display brightness.
1.5x to 2x Switchover
When VIN is less than VOUT but greater than two-thirds VOUT, the MAX8631X/Y operates in 1.5x mode. The internal current regulators regulate the LED current. As V IN drops, V M_ (or V F_ ) eventually falls below the switchover threshold of 100mV, and the MAX8631X/Y starts switching in 2x mode. When the input voltage rises above two-thirds VOUT by approximately 50mV, the MAX8631X/Y switches back to 1.5x mode.
True Shutdown is a trademark of Maxim Integrated Products, Inc.
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN MAX8631X/Y
0 ENM1 AND ENM2 OR ENF INITIAL tHI 200s 1 2 3 4 5 27 28 29 30 31 32
tSOFT-START tLO 32/32 500ns TO 250s 31/32 30/32 29/32 28/32 27/32 tHI 500ns 5/32 4/32 3/32 32/32 31/32
tSHDN 2ms (typ)
IM_ OR IF_ SHUTDOWN
2/32
1/32
SHUTDOWN
Figure 2. ENM_ and ENF Timing Diagram
Thermal Shutdown
The MAX8631X/Y includes a thermal-limit circuit that shuts down the IC at approximately +160C. Turn-on occurs after the IC cools by approximately 20C.
Applications Information
Setting the Main Output Current
SETM controls M1-M4 regulation current. Current flowing into M1, M2, M3, and M4 is a multiple of the current flowing out of SETM: IM1 = IM2 = IM3 = IM4 = K x (0.6V / RSETM) where K = 23, 69, or 230 (depending upon the state of ENM1 and ENM2; see Table 1), and RSETM is the resistor connected between SETM and GND (see the Typical Operating Circuit).
ly, the main (or flash) LEDs are enabled at full brightness. Each subsequent low-going pulse (500ns to 250s pulse width) reduces the LED current by 3.125% (1/32), so after one pulse the LED current is 96.9% (or 31/32) x ILED. The 31st pulse reduces the current to 0.03125 x ILED. The 32nd pulse sets the LED current back to ILED. Figure 2 shows a timing diagram for single-wire pulse dimming. Because soft-start is longer than the initial tHI, apply dimming pulses quickly upon startup (after initial tHI) to avoid LED current transitioning through full brightness.
Simple On/Off Control
If dimming control is not required, connect ENM1 to ENM2 for simple on/off control. Drive both ENM1 and ENM2 to a logic-level high to turn on the main LEDs. Drive both ENM1 and ENM2 to a logic-level low to turn off the main LEDs. ENF is the simple on/off control for the flash LEDs. Drive ENF to a logic-level high to turn on the flash LEDs. Drive ENF to a logic-level low to turn off the flash LEDs. In this case, LED current is set by the values of RSETM and RSETF.
Table 1. ENM1/ENM2 States
ENM1/ENM2 STATES ENM1 = low, ENM2 = low ENM1 = low, ENM2 = high ENM1 = high, ENM2 = low ENM1 = high, ENM2 = high BRIGHTNESS Shutdown 1/10 brightness 3/10 brightness Full brightness M1-M4 CURRENT 0 23 x ISETM 69 x ISETM 230 x ISETM
Dimming Using PWM into ENM1
Use ENM2 for shutdown and drive ENM1 with a PWM signal. LED brightness can be varied from 10% to full brightness based upon the duty cycle of the PWM signal. Drive ENM2 high to keep the IC on, eliminating any soft-start delay that would impede PWM control and allowing a PWM frequency up to 5kHz (Figure 3).
Setting the Flash Output Current
SETF controls the F1-F4 regulation current. Current flowing into F1, F2, F3, and F4 is a multiple of the current flowing out of SETF. IF1 = IF2 = IF3 = IF4 = N x (0.6V / RSETF) where N = 690.
Driving Fewer than 8 LEDs
When driving fewer than 8 LEDs, two different connection schemes can be used. The first scheme is shown in Figure 4 where LED drivers are connected together. This method allows increased current through the LED and effectively allows total LED current to be ILED multiplied by the number of connected drivers. The second method of connection is shown in Figure 5 where standard white LEDs are used and fewer than 8 are connected. This scheme does not alter current through each LED but ensures that the unused LED driver is properly disabled.
11
Single-Wire Pulse Dimming
For more dimming flexibility or to reduce the number of control traces, the MAX8631X/Y supports serial pulse dimming. Connect ENM1 and ENM2 together to enable single-wire pulse dimming of the main LEDs (or ENF only for single-wire pulse dimming of the flash LEDs). When ENM1 and ENM2 (or ENF) go high simultaneous-
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN MAX8631X/Y
1F 1F
INPUT 2.7V TO 5.5V 10F
C1P PIN IN GND
C1N
C2P
C2N LDO1 LDO2 1F OUTPUT UP TO 480mA 10F MAIN FLASH 1F
ON OFF PWM INPUT ON/OFF ON/OFF ENM2 ENM1 ENF ENLDO
MAX8631X MAX8631Y
OUT
M1 M2 M3 M4 F1 F2 F3 F4 SETF REFBP 0.01F PGND
VOLTAGE SELECTION
P1 P2 SETM
6.81k
4.12k
Figure 3. Dimming Using PWM Signal into ENM1
1F 1F
INPUT 2.7V TO 5.5V 10F
C1P PIN IN GND
C1N
C2P
C2N LDO1 LDO2 1F OUTPUT UP TO 480mA 10F MAIN FLASH 1F
ENM2 ENM1 ON/OFF AND VOLTAGE SELECTION ENF ENLDO P1 P2
MAX8631X MAX8631Y
OUT
M1 M2 M3 M4 F1 F2 F3 F4 SETF REFBP 0.01F PGND
SETM
6.81k
4.12k
Figure 4. Providing Increased LED Current per LED 12 ______________________________________________________________________________________
1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN MAX8631X/Y
1F 1F INPUT 2.7V TO 5.5V 10F
C1P PIN IN GND
C1N
C2P
C2N LDO1 LDO2 1F OUTPUT UP TO 240mA 10F MAIN FLASH 1F
ENM2 ENM1 ON/OFF AND VOLTAGE SELECTION ENF ENLDO P1 P2
MAX8631X MAX8631Y
OUT
M1 M2 M3 M4 F1 F2 F3 F4 SETF REFBP 0.01F PGND
SETM
6.81k
4.12k
Figure 5. Schematic for When Fewer than 8 LEDs Is Acceptable
Input Ripple
For LED drivers, input ripple is more important than output 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 CIN to 22F cuts input ripple in half with only a small increase in footprint. The 1x mode always has very low input ripple. Typical operating waveforms shown in the Typical Operating Characteristics show input ripple current in 1x, 1.5x, and 2x mode.
Table 2. P1 and P2, LDO Output Voltage Selection
P1 IN IN IN OPEN OPEN OPEN GND GND GND P2 IN OPEN GND IN OPEN GND IN OPEN GND MAX8631X 3.3 3.0 2.8 3.3 2.6 2.6 3.0 2.8 2.5 1.8 1.5 1.5 1.5 1.8 1.5 1.8 1.8 1.8 MAX8631Y 2.8 2.8 2.9 2.6 2.6 2.8 2.9 2.9 2.9 2.6 2.8 1.5 1.9 2.6 1.9 1.8 1.9 2.9 LDO1 (V) LDO2 (V) LDO1 (V) LDO2 (V)
LDO Output Voltage Selection (P1 and P2)
As shown in Table 2, the LDO output voltages, LDO1 and LDO2 are pin-programmable by the logic states of P1 and P2. P1 and P2 are tri-level inputs: IN, open, and GND. The input voltage, VIN, must be greater than the selected LDO1 and LDO2 voltages. The logic states of P1 and P2 can be programmed only during ENLDO low. Once the LDO_ voltages are programmed, their values do not change by changing P1 or P2 during ENLDO high.
Component Selection
Use only ceramic capacitors with an X5R, X7R, or better dielectric. See Table 3 for a list of recommended parts.
Connect a 1F ceramic capacitor between LDO1 and GND, and a second 1F ceramic capacitor between LDO2 and GND for 200mA applications. The LDO output capacitor's (C LDO) equivalent series resistance (ESR) affects stability and output noise. Use output capacitors with an ESR of 0.1 or less to ensure stability and optimum transient response. Connect CLDO_ as close to the MAX8631X/Y as possible to minimize the impact of PC board trace inductance.
13
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN MAX8631X/Y
Table 3. Recommended Components for Figure 1
DESIGNATION C1, C5 C3, C4, C6, C7 C8 D1-D4 D5 (D5-D8) RSETM, RSETF VALUE 10F 1F 0.01F -- -- As Required MANUFACTURER TDK TDK TDK Nichia Nichia Panasonic Vishay PART NUMBER C2012X5R0J106M C1005X5R0J105M C1005X7R1E103K NSCW215T NBCW011T -- DESCRIPTION 10F 20%, 6.3V X5R ceramic capacitors (0805) 1F 20%, 6.3V X5R ceramic capacitors (0402) 0.01F 10%, 25V X7R ceramic capacitor (0402) White LEDs White LEDs, 4 LEDs in one package 1% resistor
PC Board Layout and Routing
The MAX8631X/Y is a high-frequency switched-capacitor voltage regulator. For best circuit performance, use a solid ground plane and place CIN, COUT, C3, and C4 as close to the MAX8631X/Y as possible. There should be no vias on CIN. Connect GND and PGND to the exposed paddle directly under the IC. Refer to the MAX8631X/Y evaluation kit for an example.
Pin Configuration
ENM1 ENLDO
TOP VIEW
ENF ENM2
21
C1N
C1P PGND
20
19
18
17
P2
16
M1
15 14 M3 13 12
M4 F1 F2
22 23 24 25 26 27 28
M2
Chip Information
PROCESS: BiCMOS
OUT C2P C2N
P1
MAX8631XETI MAX8631YETI
11
10 F3 9 8
F4 SETM
+
1
PIN
2
IN
3
GND
4
LDO1
5
LDO2
6
REFBP
7
SETF
THIN QFN 4mm x 4mm, 0.4mm LEAD PITCH
14
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1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN
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.)
MAX8631X/Y
PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm
21-0139
E
1
2
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24L QFN THIN.EPS
15
1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN MAX8631X/Y
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
21-0139
E
2
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.
16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.

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