19-3688; Rev 3; 6/08 KIT ATION EVALU E L B A AVAIL 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN 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 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 ♦ Single-Wire Serial Pulse Interface for Brightness Control (32 Steps) ♦ Thermal TA Derating Function ♦ Low Input Ripple and EMI ♦ 2.7V to 5.5V Supply Voltage Range Camera Phones and Smartphones ♦ Soft-Start, Overvoltage, and Thermal-Shutdown Protection Backlighting and Flash ♦ 28-Pin Thin QFN, 4mm x 4mm Package PDAs, Digital Cameras, and Camcorders Typical Operating Circuit 1μF INPUT 2.7V TO 5.5V C1P PIN 1μF C1N C2P C2N OUT 10μF IN 10μF GND FLASH ON/OFF DUAL-LDO ON/OFF DUAL-LDO VOLTAGE SELECTION MAIN PART TEMP RANGE PIN-PACKAGE MAX8631XETI+ -40°C to +85°C 28 Thin QFN-EP* 4mm x 4mm (T2844-1) MAX8631YETI+ -40°C to +85°C 28 Thin QFN-EP* 4mm x 4mm (T2844-1) FLASH MAX8631X/Y M1 M2 PGND MAIN ON/OFF AND DIMMING OUTPUT UP TO 480mA Ordering Information *EP = Exposed pad. +Denotes a lead-free package. M3 M4 F1 F2 F3 F4 ENM1 ENM2 ENF LDO1 LDO2 ENLDO P1 CAMERA MODULE 1μF 1μF P2 SETM SETF REF 0.01μF Pin Configuration appears at end of data sheet. ________________________________________________________________ Maxim Integrated Products 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. 1 MAX8631X/Y General Description MAX8631X/Y 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN 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 = +70°C) 28-Pin Thin QFN 4mm X 4mm (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 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 = 6.8kΩ, P1 = P2 = unconnected, CREF = 0.01µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CONDITIONS MIN IN Operating Voltage Undervoltage-Lockout Threshold VIN rising or falling 2.25 Undervoltage-Lockout Hysteresis Supply Current 2.45 MAX UNITS 5.5 V 2.60 130 1MHz switching, no load, 1.5x or 2x mode 4.0 1x mode 10% setting, ENF = GND, VENLDO = VIN, ILDO1 = ILDO2 = 0A 0.4 ENM1 = ENM2 = ENF = GND, VENLDO = VIN, ILDO1 = ILDO2 = 0A 110 TA = +25°C 0.01 TA = +85°C 0.1 Shutdown Supply Current ENM1 = ENM2 = ENF = ENLDO = GND EN_ High Voltage VIN = 2.7V to 5.5V EN_ Low Voltage VIN = 2.7V to 5.5V EN_ Input Current VEN_ = 0V or 5.5V ENM_ or ENF Low Shutdown Delay tSHDN See Figure 2 2.5 ENM_ or ENF tLO See Figure 2 0.5 ENM_ or ENF tHI See Figure 2 0.5 Initial ENM_ or ENF tHI Only required for first ENM_ or ENF pulse, see Figure 2 200 P1, P2 Shutdown Input Current P1, P2 Input Impedance Thermal-Shutdown Threshold TYP 2.7 Temperature rising Thermal-Shutdown Hysteresis V mV 5.5 mA µA 5 1.4 µA V 0.4 TA = +25°C 0.01 TA = +85°C 0.1 1 V µA ms 250.0 µs µs µs 1 µA 150 kΩ +160 °C 20 °C CHARGE PUMP Overvoltage-Protection Threshold Soft-Start Time 2 VOUT rising 5 V 2 ms _______________________________________________________________________________________ 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN (VIN = 3.6V, VGND = VPGND = 0V, ENM1 = ENM2 = ENF = IN, RSETM = RSETF = 6.8kΩ, P1 = P2 = unconnected, CREF = 0.01µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CONDITIONS 1x to 1.5x or 1.5x to 2x Mode Transition Threshold MIN TYP MAX UNITS 90 100 110 mV 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 150 VIN ≥ 3.15V, VOUT = 3.9V mV 580 mA 1x mode, (VIN - VOUT) / IOUT 0.3 1.5x mode, (1.5VIN - VOUT) / IOUT 1.1 4.0 2x mode, (2VIN - VOUT) / IOUT 1.5 4.14 VOUT < 1.25V 500 mA 1 MHz 5 kΩ 0.6 V ENM_ = ENF = GND 1.0 Ω LED DRIVER SET_ Bias Voltage TA = +25°C SET_ Leakage in Shutdown ENM_ = ENF = GND TA = +25°C 0.01 TA = +85°C 0.1 SET_ Current Range 10 1 145 µA µA SETM-to-Main LED Current Ratio (IM_/ISETM) 100% setting, M1–M4 230 A/A SETF-to-Flash LED Current Ratio (IF_/ISETF) 100% setting, F1–F4 690 A/A M_, F_ Current Accuracy TA = +25°C TA = -40°C to current derating start temperature -1.25 +1.25 -4 +4 % Maximum Main LED Sink Current RSETM = 4.6kΩ, for each M_ 30 mA Maximum Flash LED Sink Current RSETF = 4.12kΩ, IF1 + IF2 + IF3 + IF4 400 mA +40 °C -1.7 %/°C Current-Derating-Function Start Temperature Current-Derating-Function Slope TA = +40°C to +85°C Dropout Voltage (Note 2) 40 1.5x and 2x Regulation Voltage TA = +25°C 0.01 TA = +85°C 0.1 M_, F_ Leakage in Shutdown ENM_ = ENF = GND LDO_ Output Voltage Accuracy ILDO_ = 150mA, relative to VOUT(NOM) (Note 3) -1.7 VLDO_ = 0V 280 Output Current Range Current Limit Soft-Start Current Limit 90 150 0 0 475 160 mV mV 1 µA +1.7 % 200 mA 750 mA mA _______________________________________________________________________________________ 3 MAX8631X/Y ELECTRICAL CHARACTERISTICS (continued) ELECTRICAL CHARACTERISTICS (continued) (VIN = 3.6V, VGND = VPGND = 0V, ENM1 = ENM2 = ENF = IN, RSETM = RSETF = 6.8kΩ, P1 = P2 = unconnected, CREF = 0.01µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CONDITIONS MIN TYP Soft-Start Done Time MAX UNITS 100 120 µs Dropout Voltage ILDO_ = 200mA (Note 4) Load Regulation VIN = 3.7V, 100µA < ILDO_ < 200mA Power-Supply Rejection ΔVOUT/ΔVIN 10Hz to 10kHz, CLDO_ = 1µF, ILDO_ = 10µA -60 dB Output Noise Voltage (RMS) 10Hz to 100kHz, CLDO_ = 1µF, ILDO_ = 10mA 40 µVRMS 320 mV 1.3 % Note 1: All devices are 100% production tested at TA = +25°C. 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 = +25°C, unless otherwise noted.) 70 15mA/LED 60 4.5mA/LED 50 40 70 60 400mA TOTAL 3.0 3.3 3.6 Li+ BATTERY VOLTAGE (V) 3.9 4.2 MAX8631X toc03 100 80 60 ILED = 4.5mA 40 ILED = 1.5mA 20 0 40 2.7 4 80 50 1.5mA/LED 160mA TOTAL VIN FALLING VIN RISING ILED = 15mA BATTERY CURRENT (mA) 80 80mA TOTAL 90 120 MAX8631 toc02 90 100 EFFICIENCY PLED/PBATT (%) MAX8631X toc01 100 BATTERY CURRENT vs. SUPPLY VOLTAGE DRIVING FOUR MAIN LEDs EFFICIENCY vs. Li+ BATTERY VOLTAGE DRIVING FLASH LED MODULE EFFICIENCY vs. Li+ BATTERY VOLTAGE DRIVING FOUR MAIN LEDs EFFICIENCY PLED/PBATT (%) MAX8631X/Y 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN 2.7 3.0 3.3 3.6 Li+ BATTERY VOLTAGE (V) 3.9 4.2 2.7 3.0 3.3 3.6 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 3.9 4.2 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN 500 IFLASH = 160mA 400 IFLASH = 80mA 300 200 100 2.7 3.0 3.3 3.6 3.9 150mA, BOTH LDOs 110 MAX8631X toc06 0.8 0.6 ILED = 4.5mA 0.4 ILED = 1.5mA 100 0.2 90 0 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 5.5 5.1 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) INPUT RIPPLE VOLTAGE vs. SUPPLY VOLTAGE WITH FLASH AND MAIN LEDs LED CURRENT MATCHING vs. SUPPLY VOLTAGE WITH FOUR MAIN LEDs LED CURRENT MATCHING vs. SUPPLY VOLTAGE WITH FOUR FLASH LEDs 6 IFLASH = 100mA 5 4 3 15.6 15.4 15.2 15.0 14.8 14.6 2 14.4 1 14.2 0 14.0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 101.5 101.0 100.5 100.0 99.5 99.0 98.5 98.0 2.7 5.5 MAX8631X toc09 15.8 FLASH LED CURRENT (mA) IFLASH = 40mA 7 102.0 MAX8631X toc08 IFLASH = 10mA 16.0 MAIN LED CURRENT (mA) MAX8631X toc07 FOUR MAIN LEDs AT 15mA EACH 8 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 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) LED CURRENT vs. AMBIENT TEMPERATURE WITH FOUR MAIN LEDs LED CURRENT vs. AMBIENT TEMPERATURE WITH FLASH INDIVIDUAL MAIN LED CURRENT vs. RSETM 50 40 30 20 400 100 350 300 250 200 150 5.5 MAX8631X toc12 60 450 MAIN LED CURRENT (mA) MAX8631X toc10 70 TOTAL LED CURRENT (mA) INPUT RIPPLE (mVRMS) NO LOAD, BOTH LDOs 120 4.2 10 TOTAL LED CURRENT (mA) 130 ILED = 15mA 1.0 80 0 9 140 INPUT RIPPLE (mVRMS) IFLASH = 400mA 150 1.2 MAX8631X toc05 700 VENM = VENF = 0V, VENLDO = VIN MAX8631X toc11 BATTERY CURRENT (mA) 800 160 GROUND PIN SUPPLY CURRENT (μA) MAX8631X toc04 900 600 INPUT RIPPLE VOLTAGE vs. SUPPLY VOLTAGE WITH FOUR MAIN LEDs LDO GROUND PIN SUPPLY CURRENT vs. SUPPLY VOLTAGE BATTERY CURRENT vs. SUPPLY VOLTAGE DRIVING FLASH 10 100 10 50 0 0 -40 -15 10 35 60 AMBIENT TEMPERATURE (°C) 85 1 -40 -15 10 35 60 AMBIENT TEMPERATURE (°C) 85 1 10 100 RSETM (kΩ) _______________________________________________________________________________________ 5 MAX8631X/Y Typical Operating Characteristics (continued) (VIN = VEN_ = 3.6V, circuit of Figure 1, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VIN = VEN_ = 3.6V, Circuit of Figure 1, TA = +25°C, unless otherwise noted.) INDIVIDUAL FLASH LED CURRENT vs. RSETF OPERATING WAVEFORMS (1x MODE) MAX8631X toc14 MAX8631X toc13 1000 FLASH LED CURRENT (mA) MAX8631X/Y 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN VOUT 50mV/div AC-COUPLED VIN 20mV/div AC-COUPLED IIN 2mA/div AC-COUPLED 100 10 4 MAIN LEDS AT 20mA EACH 1 1 10 100 400ns/div RSETF (kΩ) OPERATING WAVEFORMS (2x MODE) OPERATING WAVEFORMS (1.5x MODE) MAX8631X toc16 MAX8631X toc15 VOUT 50mV/div AC-COUPLED VIN 20mV/div AC-COUPLED VOUT 50mV/div AC-COUPLED VIN 20mV/div AC-COUPLED 4 MAIN LEDS AT 20mA EACH, FLASH AT 400mA TOTAL 2mA/div AC-COUPLED IIN 2mA/div AC-COUPLED IIN 4 MAIN LEDS AT 20mA EACH 400ns/div 400ns/div STARTUP AND SHUTDOWN MAIN LED RESPONSE STARTUP AND SHUTDOWN FLASH LED RESPONSE MAX8631X toc17 MAX8631X toc18 5V/div 0V VENM_ 5V/div 0V VENF 4 MAIN LEDS AT 20mA EACH, 400mA TOTAL FLASH 4 MAIN LEDS AT 20mA EACH 100mA/div IOUT 0A 500mA/div 0A IIN 500mA/div VOUT 0A VOUT 5V/div 0V 5V/div 0V 1ms/div 6 IOUT 1ms/div _______________________________________________________________________________________ 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN LDO DROPOUT VOLTAGE vs. OUTPUT CURRENT SINGLE-WIRE DIMMING RESPONSE MAX8631X toc19 500mA/div IOUT 0A 120 DROPOUT VOTLAGE (mV) 5V/div 0V VENM1, VENM2 MAX8631X toc20 140 100 80 60 40 VOUT 2V/div 20 0V 0 0 10ms/div 50 100 200 150 OUTPUT CURRENT (mA) LDO OUTPUT VOLTAGE ACCURACY vs. OUTPUT CURRENT XMAX8631X toc21 0.8 OUTPUT VOLTAGE ACCURACY (%) LOAD-TRANSIENT RESPONSE MAX8631X toc22 1.0 0.6 VLDO_ = 2.6V 50mV/div AC-COUPLED VLDO_ 0.4 0.2 100mA 0 -0.2 -0.4 ILDO_ -0.6 1mA -0.8 -1.0 0 50 100 150 200 10μs/div OUTPUT CURRENT (mA) LOAD-TRANSIENT RESPONSE NEAR DROPOUT MAX8631X toc23 VIN - VOUT = 77mV, VLDO_ = 2.6V 50mV/div AC-COUPLED VLDO_ 100mA ILDO_ 1mA 10μs/div _______________________________________________________________________________________ 7 MAX8631X/Y Typical Operating Characteristics (continued) (VIN = VEN_ = 3.6V, circuit of Figure 1, TA = +25°C, unless otherwise noted.) MAX8631X/Y 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN C3 1μF INPUT 2.7V TO 5.5V C1 10μF C1P PIN IN C1N C4 1μF C2P C2N LDO1 LOWDROPOUT LINEAR REGULATORS 1x/1.5x/2x REGULATING CHARGE PUMP GND C6 1μF LDO2 C7 1μF PGND ERROR AMP 1 OUTPUT UP TO 480mA OUT C5 10μF OVD 1.25V REFBP C8 0.01μF CONTROL AND REFERENCE 0.15V ENM1 ENM2 ENF SELMIN FLASH CONTROL M1 D1 M2 D2 M3 D3 M4 D4 F1 D5 F2 D6 F3 D7 F4 D8 MAIN CONTROL ENLDO 0.6V P1 P2 IN + + + + – – – – ERROR AMP 2 GND SETM RSETM 6.81kΩ IN + + + + – – – – ERROR AMP 3 MAX8631X MAX8631Y SETF RSETF 4.12kΩ GND Figure 1. Functional Diagram and Application Circuit 8 _______________________________________________________________________________________ 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN PIN NAME FUNCTION 1 PIN 2 IN Chip Supply Voltage Input. Bypass to GND with a 10µF 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. 3 GND Ground. Connect GND to system ground and the input bypass capacitor as close to the IC as possible. 4 LDO1 LDO1 Output. Bypass with a 1µF ceramic capacitor to GND. LDO1 is pulled to ground through an internal 400kΩ during shutdown. 5 LDO2 LDO2 Output. Bypass with a 1µF ceramic capacitor to GND. LDO2 is pulled to ground through an internal 400kΩ during shutdown. 6 REFBP Reference Filter. Bypass REFBP with a 0.01µF ceramic capacitor to GND. 7 SETF 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. 8 SETM 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. 9–12 F4–F1 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. 13–16 M4–M1 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. 17 P2 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. 18 ENLDO 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. 19 ENM2 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. The dimming technique is discussed in the Applications Information section. 20 ENM1 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. The dimming technique is discussed in the Applications Information section. 21 ENF 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. The dimming technique is discussed in the Applications Information section. 22 C1N Transfer Capacitor 1 Negative Connection. Connect a 1µF ceramic capacitor between C1P and C1N. C1N is internally shorted to IN during shutdown. Supply Voltage Input. Bypass to PGND with a 10µF ceramic capacitor. The input voltage range is 2.7V to 5.5V. PIN is high impedance during shutdown. _______________________________________________________________________________________ 9 MAX8631X/Y Pin Description 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN MAX8631X/Y Pin Description (continued) PIN NAME FUNCTION Transfer Capacitor 1 Positive Connection. Connect a 1µF ceramic capacitor between C1P to C1N. During shutdown, if OUT > IN, C1P is shorted to OUT. If OUT < IN, C1P is shorted to IN. 23 C1P 24 PGND Power Ground. Connect PGND to system ground. PGND is used for charge-pump switching currents. 25 OUT Charge-Pump Output. Bypass OUT to GND with a 10µF ceramic capacitor. Connect to the anodes of all the LEDs. OUT is internally pulled to ground through a 5kΩ resistor during shutdown. 26 C2P Transfer Capacitor 2 Positive Connection. Connect a 1µF ceramic capacitor between C2P to C2N. During shutdown, if OUT > IN, C2P is shorted to OUT. If OUT < IN, C2P is shorted to IN. 27 C2N Transfer Capacitor 2 Negative Connection. Connect a 1µF ceramic capacitor between C2P and C2N. C2N is internally shorted to IN during shutdown. 28 P1 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. — EP 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. 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. 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. 10 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. True Shutdown™ Mode When ENM1, ENM2, and ENF are simultaneously held low for 2.5ms 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 5kΩ 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 +43°C, 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. ______________________________________________________________________________________ 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN ENM1 AND ENM2 OR ENF INITIAL tHI ≥ 200μs 1 2 3 4 5 27 28 29 30 31 32 tSOFT-START tLO 32/32 IM_ OR IF_ 500ns TO 250μs 31/32 30/32 29/32 28/32 27/32 SHUTDOWN tSHDN tHI ≥500ns 5/32 32/32 31/32 4/32 3/32 2/32 1/32 (2.5ms) 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 +160°C. Turn-on occurs after the IC cools by approximately 20°C. 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 = 230, and RSETM is the resistor connected between SETM and GND (see the Typical Operating Circuit). Table 1. ENM1/ENM2 States ENM1/ENM2 STATES ENM1 = low, ENM2 = low ENM1 = high, ENM2 = high BRIGHTNESS M1–M4 CURRENT Shutdown 0 Full brightness 230 x ISETM 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. 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). See Figure 3. When ENM1 and ENM2 (or ENF) 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 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. 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. 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 22µF cuts input ripple in half with only a small increase in footprint. The 1x mode always has very low input ripple. ______________________________________________________________________________________ 11 MAX8631X/Y 0 MAX8631X/Y 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN 1μF INPUT 2.7V TO 5.5V 10μF C1P PIN 1μF C1N C2P C2N LDO1 1μF GND MAIN ON/OFF AND DIMMING FLASH ON/OFF AND DIMMING ON/OFF VOLTAGE SELECTION 1μF LDO2 IN MAX8631X MAX8631Y ENM2 OUTPUT UP TO 480mA OUT MAIN 10μF FLASH ENM1 M1 M2 ENF M3 M4 F1 F2 F3 F4 ENLDO P1 P2 SETM SETF REFBP PGND 0.01μF 6.81kΩ 4.12kΩ Figure 3. Dimming Using Single-Wire, Serial-Pulse Interface 1μF INPUT 2.7V TO 5.5V 10μF C1P PIN 1μF C1N C2P C2N LDO1 1μF LDO2 IN 1μF GND OUT MAX8631X MAX8631Y ENM2 OUTPUT UP TO 480mA 10μF MAIN FLASH ENM1 ON/OFF AND VOLTAGE SELECTION M1 M2 ENF M3 M4 F1 F2 F3 F4 ENLDO P1 P2 SETM SETF REFBP PGND 0.01μF 6.81kΩ 4.12kΩ 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 INPUT 2.7V TO 5.5V 10μF C1P PIN MAX8631X/Y 1μF 1μF C1N C2P C2N LDO1 1μF LDO2 IN 1μF GND OUT MAX8631X MAX8631Y ENM2 OUTPUT UP TO 240mA 10μF MAIN FLASH ENM1 ON/OFF AND VOLTAGE SELECTION M1 M2 ENF M3 M4 F1 F2 F3 F4 ENLDO P1 P2 SETM SETF REFBP PGND 0.01μF 6.81kΩ 4.12kΩ Figure 5. Schematic for When Fewer than 8 LEDs Is Acceptable 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 MAX8631X MAX8631Y P1 P2 IN IN IN OPEN 3.0 1.5 2.8 2.8 IN GND 2.8 1.5 2.9 1.5 OPEN IN 3.3 1.5 2.6 1.9 OPEN OPEN 2.6 1.8 2.6 2.6 OPEN GND 2.6 1.5 2.8 1.9 GND IN 3.0 1.8 2.9 1.8 Component Selection GND OPEN 2.8 1.8 2.9 1.9 Use only ceramic capacitors with an X5R, X7R, or better dielectric. See Table 3 for a list of recommended parts. Connect a 1µF ceramic capacitor between LDO1 and GND, and a second 1µF 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 0.1Ω 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. GND GND 2.5 1.8 2.9 2.9 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. LDO1 (V) LDO2 (V) LDO1 (V) LDO2 (V) 3.3 1.8 2.8 2.6 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. ______________________________________________________________________________________ 13 Table 3. Recommended Components for Figure 1 DESIGNATION VALUE MANUFACTURER PART NUMBER C1, C5 10µF TDK C2012X5R0J106M 10µF ±20%, 6.3V X5R ceramic capacitors (0805) DESCRIPTION C3, C4, C6, C7 1µF TDK C1005X5R0J105M 1µF ±20%, 6.3V X5R ceramic capacitors (0402) 0.01µF ±10%, 25V X7R ceramic capacitor (0402) C8 0.01µF TDK C1005X7R1E103K D1–D4 — Nichia NSCW215T White LEDs D5 (D5–D8) — Nichia NBCW011T White LEDs, 4 LEDs in one package RSETM, RSETF As Required Panasonic — Vishay 1% resistor Pin Configuration Chip Information PROCESS: BiCMOS T2844-1 21-0139 ENM1 ENM2 ENLDO P2 M1 M2 16 15 C1N 22 14 M3 C1P 23 13 M4 PGND 24 12 F1 OUT 25 11 F2 C2P 26 C2N 27 P1 28 MAX8631XETI MAX8631YETI 10 F3 + 1 2 3 4 5 6 7 SETF 28 TQFN-EP 17 REFBP DOCUMENT NO. 18 LDO2 PACKAGE CODE 19 LDO1 PACKAGE TYPE 20 GND For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. 21 IN Package Information ENF TOP VIEW PIN MAX8631X/Y 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN THIN QFN 4mm x 4mm, 0.4mm LEAD PITCH 14 ______________________________________________________________________________________ 9 F4 8 SETM 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN REVISION NUMBER REVISION DATE 3 6/08 DESCRIPTION Removed PWM dimming control feature and updated ENM_ and ENF low shutdown delay EC values PAGES CHANGED 1, 2, 9–12, 14 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15 © 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc. MAX8631X/Y Revision History