MAX1575ETE/V+

19-3097; Rev 2; 8/05 KIT ATION EVALU E L B A AVAIL White LED 1x/1.5x Charge Pump for Main and Sub-Displays The MAX1575 charge pump drives up to four white LEDs in the main display and up to two white LEDs in the sub-display with regulated constant current for uniform intensity. By utilizing adaptive 1x/1.5x chargepump modes and very-low-dropout current regulators, it achieves high efficiency over the full 1-cell lithiumbattery input voltage range. A 1MHz fixed-frequency switching allows for tiny external components, and the regulation scheme is optimized to ensure low EMI and low input ripple. The MAX1575 uses an external resistor to set the fullscale 100% LED current. Two enable inputs, ENM and ENS, are used for simple on/off controls for the main and sub-displays, respectively. By repeatedly pulsing either enable input, the LEDs can be dimmed in multiple steps down to 5%. Once the desired brightness is set, the MAX1575 maintains that brightness setting as long as the enable input is kept high. If an enable input is kept low for more than 2ms, the LED current for the respective display is set to zero. If both enable inputs are kept low for more than 2ms, the MAX1575 enters shutdown. The MAX1575 is available in a 16-pin 4mm x 4mm thin QFN package (0.8mm max height). Applications Cell Phones with Main and Sub-Displays Features ♦ Powers Main and Sub-Display LEDs ♦ 85% Average Efficiency (PLED / PBATT) Over Li+ Battery Discharge ♦ 2% LED Current Matching ♦ Up to 30mA/LED Drive Capability ♦ Adaptive 1x/1.5x Mode Switchover ♦ Low Input Ripple and EMI ♦ Individual 5% to 100% Dimming Through Single-Wire Serial Pulse Interface ♦ Low 0.1µA Shutdown Current ♦ 2.7V to 5.5V Supply Voltage Range ♦ Soft-Start Limits Inrush Current ♦ Output-Overvoltage Protection ♦ Thermal-Shutdown Protection ♦ 16-Pin Thin QFN 4mm x 4mm Package Ordering Information PART TEMP RANGE PIN-PACKAGE MAX1575ETE -40°C to +85°C 16 Thin QFN 4mm x 4mm MAX1575ETE+ -40°C to +85°C 16 Thin QFN 4mm x 4mm + Denotes lead-free package. Typical Operating Circuit PDAs/Smart Phones with Up to Six White LEDs 1μF Pin Configuration C1P GND LED1 LED2 LED3 TOP VIEW 12 11 10 9 2.7V TO 5.5V LED4 IN 14 7 LED5 6 LED6 5 ENM 1 2 3 4 OUT SET ENS + C2P C1P 16 THIN QFN 4mm x 4mm 1μF MAX1575 8 MAX1575 OUT IN 1μF C1N 13 C2N 15 C1N GND MAIN LED1 LED2 ENABLE MAIN ON/OFF AND DIMMING ENM ENABLE SUB ON/OFF AND DIMMING ENS LED3 LED4 LED5 SUB SET LED6 RSET C2P C2N 1μF ________________________________________________________________ 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 MAX1575 General Description MAX1575 White LED 1x/1.5x Charge Pump for Main and Sub-Displays ABSOLUTE MAXIMUM RATINGS IN, OUT, ENM, ENS to GND..................................-0.3V to +6.0V SET, LED_, C1N, C2N to GND.....................-0.3V to (VIN + 0.3V) C1P, C2P to GND.............................................................-0.3V to the greater of (VOUT + 1V) or (VIN + 1V) OUT Short Circuit to GND ..........................................Continuous Continuous Power Dissipation (TA = +70°C) 16-Pin Thin QFN 4mm x 4mm (derate 16.9 mW/°C above +70°C) ............................1349mW 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 = 0V, ENM = ENS = IN, RSET = 6.81kΩ, CIN = C1 = C2 = COUT = 1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CONDITIONS IN Operating Voltage Undervoltage-Lockout Threshold MIN No-Load Supply Current Shutdown Supply Current 2.25 SET-to-LED_ Current Ratio (ILED_ / ISET) LED Current Accuracy LED-to-LED Current Matching (Note 2) Maximum LED_ Sink Current V 5 V 1MHz switching in 1.5x mode 2 No switching in 1x mode,10% setting 0.5 ENM = ENS = OUT = GND 0.1 ENM = ENS = GND mA 2 ms 0.6 V 0.01 1 10 130 TA = -40°C to +85°C 30 130 100% setting 234 TA = +25°C to +85°C -8 TA = -40°C to +85°C -9.5 µA 2 TA = 0°C to +85°C ±2 µA A/A +8 +9.5 ±1.5 µA -5 TA = -40°C to +85°C -6.5 RSET = 4.53kΩ 27.4 30.0 60 100 mV 90 100 110 mV 0.01 1 µA 1 2.5 4.2 10 (Note 3) VLED falling LED Leakage in Shutdown ENM = ENS = GND, VLED_ = 5.5V Maximum OUT Current VIN ≥ 3.4V, VOUT = 3.9V, 100% setting 1.5x mode (1.5 x VIN - VOUT) / IOUT Switching Frequency ENM = ENS = GND ENM, ENS High Voltage VIN = 2.7V to 5.5V ENM, ENS Low Voltage VIN = 2.7V to 5.5V ENM, ENS Input Current VEN_ = 0V or 5.5V Shutdown Delay From falling edge of ENM and ENS +6.5 mA Ω 1 MHz 5 kΩ 1.6 1.0 % mA 120 1x mode (VIN - VOUT) / IOUT OUT Pulldown Resistance +5 % TA = +25°C to +85°C LED_ 1x-to-1.5x Transition Threshold 2 V 2.60 VOUT rising LED_ Dropout Voltage Open-Loop OUT Resistance 5.5 2.45 mV SET Bias Voltage SET Current Range UNITS 35 Soft-Start Time SET Leakage in Shutdown MAX 2.7 VIN falling Undervoltage-Lockout Hysteresis OUT Overvoltage-Protection Threshold TYP V 0.4 V 0.01 1 µA 2 3.3 ms _______________________________________________________________________________________ White LED 1x/1.5x Charge Pump for Main and Sub-Displays (VIN = 3.6V, VGND = 0V, ENM = ENS = IN, RSET = 6.81kΩ, CIN = C1 = C2 = COUT = 1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS 500 µs tLO (ENM, ENS) (Figure 1) 0.5 tHI (ENM, ENS) (Figure 1) 0.5 µs 50 µs Initial tHI (ENM, ENS) (Figure 1) Only required for first EN_ pulse Thermal-Shutdown Threshold +160 °C Thermal-Shutdown Hysteresis 20 °C Note 1: Specifications to -40°C are guaranteed by design and not production tested. Note 2: LED current matching is defined as: (ILED - IAVG) / IAVG Note 3: Dropout voltage is defined as the LED_-to-GND voltage at which current into the LED drops 10% from the LED current at VLED_ = 0.2V. Typical Operating Characteristics (VIN = 3.6V, ENM = ENS = IN, circuit of Figure 2, TA = +25°C, unless otherwise noted.) INPUT CURRENT vs. SUPPLY VOLTAGE DRIVING SIX WHITE LEDs 20mA/LED 60 50 2mA/LED 8mA/LED 40 140 120 100 SUPPLY VOLTAGE FALLING 8mA/LED 80 200 180 60 40 30 20 3.0 3.3 3.6 3.9 100 80 60 8mA/LED 2mA/LED 20 0 2.7 4.2 20mA/LED 120 3.0 3.3 3.6 4.2 3.9 2.7 3.0 3.3 3.6 3.9 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) INPUT CURRENT vs. SUPPLY VOLTAGE DRIVING TWO WHITE LEDs INPUT RIPPLE vs. SUPPLY VOLTAGE DRIVING SIX WHITE LEDs LED CURRENT MATCHING vs. SUPPLY VOLTAGE 120 100 8mA/LED 80 2mA/LED 60 50 20mA/LED 40 30 8mA/LED 20 40 0 3.0 3.3 3.6 SUPPLY VOLTAGE (V) 3.9 4.2 MAX1575 toc06 20 19 17 0 2.7 4.2 18 2mA/LED 10 20 21 LED CURRENT (mA) 20mA/LED 140 60 INPUT RIPPLE (mVP-P) SUPPLY VOLTAGE FALLING 160 22 MAX1575 toc05 180 70 MAX1575 toc04 200 INPUT CURRENT (mA) 2mA/LED 0 2.7 140 40 20 SUPPLY VOLTAGE FALLING SUPPLY VOLTAGE FALLING 160 INPUT CURRENT (mA) 70 20mA/LED 160 INPUT CURRENT (mA) 80 180 MAX1575 toc02 90 EFFICIENCY (%) 200 MAX1575 toc01 100 INPUT CURRENT vs. SUPPLY VOLTAGE DRIVING FOUR WHITE LEDs MAX1575 toc03 EFFICIENCY vs. SUPPLY VOLTAGE DRIVING SIX WHITE LEDs 2.7 3.1 3.5 3.9 4.3 4.7 SUPPLY VOLTAGE (V) 5.1 5.5 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 3 MAX1575 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (VIN = 3.6V, ENM = ENS = IN, circuit of Figure 2, TA = +25°C, unless otherwise noted.) OUTPUT CURRENT vs. SUPPLY VOLTAGE DRIVING SIX LEDs AT 20mA EACH LED CURRENT (mA) 121 120 119 MAX1575 toc09 MAX1575 toc08 122 OPERATING WAVEFORMS (1x) LED CURRENT vs. RSET 100 MAX1575 toc07 123 OUTPUT CURRENT (mA) MAX1575 White LED 1x/1.5x Charge Pump for Main and Sub-Displays VOUT 200mV/div AC-COUPLED VIN 50mV/div AC-COUPLED IIN 50mA/div 10 118 100% BRIGHTNESS SETTING 0mA 1 117 2.7 3.1 3.5 3.9 4.3 4.7 5.1 1 5.5 10 RSET (kΩ) SUPPLY VOLTAGE (V) MAX1575 toc12 MAX1575 toc11 MAX1575 toc10 VIN MAIN STARTUP WITH SUB-DISPLAY ON STARTUP WAVEFORMS OPERATING WAVEFORMS (1.5x) VOUT 400ns/div 100 VENM 200mV/div AC-COUPLED AND VENS 5V/div 50mV/div AC-COUPLED 100mA/div IIN 5V/div VENM IIN 100mA/div 0 0 50mA/div IIN 2V/div VOUT VOUT 500mV/div 0 0 1ms/div 1ms/div 400ns/div DIMMING RESPONSE LINE TRANSIENT 3.8V TO 3.3V TO 3.8V MAX1575 toc13 MAX1575 toc14 2V/div VENM AND VENS 50mA/div VIN 1V/div 1V/div AC-COUPLED VOUT IOUT 0 50mA/div IOUT 2V/div VOUT 0mA 10ms/div 4 40μs/div _______________________________________________________________________________________ White LED 1x/1.5x Charge Pump for Main and Sub-Displays PIN NAME 1 C2P Transfer-Capacitor 2 Positive Connection. Connect a 1µF ceramic capacitor from C2P to C2N. 2 OUT Output. Connect a 1µF ceramic capacitor from OUT to GND. Connect OUT to the anodes of all the LEDs. OUT is internally pulled down with 5kΩ during shutdown. 3 SET Current-Set Input. Connect a resistor (RSET) from SET to GND to set the maximum LED current. ILED(MAX) = 234 × 0.6V / RSET. SET is internally biased to 0.6V. SET is high impedance during shutdown. ENS Enable and Dimming Control for LED5 and LED6 (Sub-Display). The first time ENS goes high (50µs min), LED5 and LED6 turn on at 100% brightness. Pulsing ENS low dims the LEDs in multiple steps. If ENS is held low for more than 2ms (typ), LED5 and LED6 turn off. When ENM and ENS are both held low for more than 2ms (typ), the IC goes into shutdown mode. See Figure 1. 5 ENM Enable and Dimming Control for LED1–LED4 (Main Display). The first time ENM goes high (50µs min), LED1–LED4 turn on at 100% brightness. Pulsing ENM low dims the LEDs in multiple steps. If ENM is held low for more than 2ms (typ), LED1–LED4 turn off. When ENM and ENS are both held low for more than 2ms (typ), the IC goes into shutdown mode. See Figure 1. 6 LED6 7 LED5 8 LED4 9 LED3 10 LED2 11 LED1 12 GND 13 C1N 4 14 IN 15 C2N 16 C1P — EP FUNCTION Sub-Display LEDs Cathode Connection. Current flowing into LED_ is described in the ENS and SET descriptions above. The charge pump regulates the lowest-enabled LED_ voltage to 180mV. Connect LED_ to IN if the LED is not populated. LED_ is high impedance during shutdown. Main-Display LEDs Cathode Connection. Current flowing into LED_ is described in the ENM and SET descriptions above. The charge pump regulates the lowest-enabled LED_ voltage to 180mV. Connect LED_ to IN if the LED is not populated. LED_ is high impedance during shutdown. Ground. Connect GND as close as possible to system ground and to the ground of the input bypass capacitor. Transfer-Capacitor 1 Negative Connection. Connect a 1µF ceramic capacitor from C1P to C1N. Supply Voltage Input. Connect a 1µF ceramic capacitor from IN to GND. The input voltage range is 2.7V to 5.5V. IN is high impedance during shutdown. Transfer-Capacitor 2 Negative Connection. Connect a 1µF ceramic capacitor from C2P to C2N. Transfer-Capacitor 1 Positive Connection. Connect a 1µF ceramic capacitor from C1P to C1N. Exposed Paddle. Connect the exposed paddle to GND. Detailed Description The MAX1575 charge pump drives up to four white LEDs in the main display and up to two white LEDs in the sub-display with regulated constant current for uniform intensity. By utilizing adaptive 1x/1.5x chargepump 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. 1x to 1.5x Switchover When VIN is higher than VOUT, the MAX1575 operates in 1x mode and VOUT is pulled up to VIN. The internal current regulators regulate the LED current. As VIN drops, VLED_ eventually falls below the switchover threshold of 100mV and the MAX1575 starts switching in 1.5x mode. When the input voltage rises above VOUT by about 50mV, the MAX1575 switches back to 1x mode. Soft-Start The MAX1575 includes soft-start circuitry to limit inrush current at turn-on. When starting up, 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 determines if 1x or 1.5x mode is required. In the case of 1x mode, the soft-start is terminated and normal operation begins. During the soft-start time, the output current is set to 5% of the maximum set by RSET. In the case of 1.5x mode, soft-start operates until the lowest of LED1–LED6 reaches regulation. If an overload condition occurs, soft-start repeats every 2ms. If the output is shorted to ground (or