19-2847; Rev 2; 8/05 White LED 1x/1.5x Charge Pump in UCSP and Thin QFN The MAX1573 fractional charge pump drives up to four white LEDs with regulated constant current for uniform intensity. By utilizing proprietary adaptive 1x/1.5x modes and ultra-low-dropout current regulators, it maintains the highest possible efficiency over the full 1-cell Li+ battery input voltage range. The 1MHz fixedfrequency switching allows for tiny external components and the regulation scheme is optimized to ensure low EMI and low input ripple. An external resistor sets the full-scale LED current, while two digital inputs control on/off and select amongst three levels of brightness. A pulse-width modulation (PWM) signal can also be used to modulate LED brightness, requiring no additional components. The MAX1573 is available in the tiny chip-scale UCSP™ (4 x 4 grid) and 16-pin thin QFN packages. Features ♦ Proprietary Adaptive 1x/1.5x Modes ♦ High Efficiency (PLEDs/PBATT), Up to 92% ♦ 0.2% LED Current Matching ♦ 28mA/LED Drive Capability ♦ Low Input Ripple and EMI ♦ Eliminates Ballast Resistors ♦ Logic or PWM Dimming Control ♦ Low 0.1µA Shutdown Current ♦ 2.7V to 5.5V Input Voltage Range ♦ Soft-Start Limits Inrush Current ♦ Output Overvoltage Protection ♦ Thermal Shutdown Protection ♦ No External Schottky Diode Required Applications ♦ Tiny UCSP (2.1mm x 2.1mm x 0.6mm) and Thin QFN (4mm x 4mm) Packages Ordering Information Cell Phones, Smart Phones PDAs, Digital Cameras, Camcorders MP3 Players Other Handhelds with Color Displays PART MAX1573EBE-T MAX1573ETE MAX1573ETE+ TEMP RANGE -40°C to +85°C -40°C to +85°C -40°C to +85°C PIN-PACKAGE 14 UCSP (4 x 4) 16 Thin QFN 16 Thin QFN + Denotes lead-free package. VIN 2.7V TO 5.5V C1N C1P C2N C2P OUT IN VOUT UP TO 4 LEDS 1μF 1μF ON/OFF AND DIMMING CONTROL EN1 MAX1573 13 IN 14 LED3 LED4 12 11 10 9 8 LED1 7 LED2 MAX1573 LED1 LED2 EN2 CIN GND TOP VIEW 1μF 1μF Pin Configurations N.C. Typical Operating Circuit C2N 15 6 SET C1P 16 5 EN2 2 3 4 N.C. RSET 1 EN1 GND C2P LED4 SET OUT LED3 THIN QFN 4mm × 4mm A "+" SIGN WILL REPLACE THE FIRST PIN INDICATOR ON LEAD-FREE PACKAGES. Pin Configurations continued at end of data sheet. UCSP is a trademark of Maxim Integrated Products, Inc. ________________________________________________________________ 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 MAX1573 General Description MAX1573 White LED 1x/1.5x Charge Pump in UCSP and Thin QFN ABSOLUTE MAXIMUM RATINGS IN, OUT, EN1, EN2 to GND ...................................-0.3V to +6.0V SET, LED1, LED2, LED3, LED4 to GND ......-0.3V to (VIN + 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) OUT Short Circuit to GND ..........................................Continuous Continuous Power Dissipation (TA = +70°C) 14-Bump UCSP (derate 7.36mW/°C above +70°C) ....589mW 16-Pin Thin QFN (derate 16.9mW/°C above +70°C) .1349mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°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 = VEN1 = VEN2 = 3.6V, CIN = C1 = C2 = COUT = 1µF, TA = -40°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER CONDITIONS IN Operating Voltage MIN Undervoltage Lockout Threshold VIN rising or falling, 35mV hysteresis Supply Current Switching, no load, ISET = 130µA Shutdown Supply Current EN1 = EN2 = OUT = GND, TA = +25°C 2.25 Soft-Start Completion Time MAX UNITS 5.5 V 2.45 2.60 V 2 4 mA 0.1 10 µA 2.1 SET Bias Voltage SET Leakage in Shutdown TYP 2.7 0.570 EN1 = EN2 = GND, TA = +25°C SET Current Range ms 0.6 0.630 V 0.01 1 µA 130 µA 40 EN1 = EN2 = IN 190 219 245 EN1 = IN, EN2 = GND 58 66 74 EN1 = GND, EN2 = IN 19.5 22 25.0 SET to LED_ Current Ratio (ILED/ISET) ISET = 60µA LED_ Current Accuracy EN1 = EN2 = IN, RSET = 4.64kΩ, TA = 0°C to +85°C ±0.6 % LED_ Current Matching ISET = 130µA, TA = 0°C to +85°C (Note 2) ±0.2 % Maximum LED_ Sink Current ISET = 130µA, EN1 = EN2 = IN LED_ Dropout Voltage ISET = 87µA (Note 3) LED_ Minimum Regulation Voltage (1.5x Mode) EN1 = EN2 = IN, ISET = 87µA LED Leakage in Shutdown EN1 = EN2 = GND, VLED = 5.5V, TA = +25°C Maximum OUT Current VIN ≥ 3.4V, VOUT ≥ 3.9V, EN1 = EN2 = IN Open-Loop OUT Resistance 25.9 100 mA 40 80 mV 150 200 mV 0.01 1 120 1.5 1.5x mode (1.5 x VIN - VOUT) / IOUT 10 1 VIN = 2.7V to 5.5V µA mA 1x mode (1 x VIN - VOUT) / IOUT Switching Frequency EN1, EN2 Logic High Voltage 28 A/A Ω MHz 1.6 V EN1, EN2 Logic Low Voltage VIN = 2.7V to 5.5V EN1, EN2 Input Current VEN_ = GND or 5.5V, TA = +25°C 0.01 Thermal-Shutdown Threshold 20°C hysteresis 160 0.4 V 1 µA °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 the LED_ current drops 10% from the value at VLED = 200mV. 2 _______________________________________________________________________________________ White LED 1x/1.5x Charge Pump in UCSP and Thin QFN EFFICIENCY (PLEDs/PBATT) vs. Li+ BATTERY DISCHARGE EFFICIENCY (PLEDs/PBATT) vs. SUPPLY VOLTAGE 1/10 70 80 70 60 60 50 50 3.8 3.7 3.6 3.2 Li+ BATTERY VOLTAGE, TIME-WEIGHTED (V) 6 5 4 3 3/10 2 3.6 3.8 4.0 4.2 LED4 19 LED2 17 LED3 15 LED1 14 13 4.2 17.0 16.9 16.8 16.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) LED CURRENT vs. RSET TYPICAL OPERATING WAVEFORMS IN 1x MODE 25 5.5 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 TEMPERATURE (°C) TYPICAL OPERATING WAVEFORMS IN 1.5x MODE MAX1573 toc08 MAX1573 toc07 30 MAX1573 toc03 17.1 16.6 4.0 4.2 17.2 10 3.8 4.0 17.3 0 3.6 3.8 17.4 16.7 3.4 3.6 17.5 11 3.2 3.4 LED CURRENT vs. TEMPERATURE 18 16 3.2 SUPPLY VOLTAGE (V) 1 3.0 1/10 3.0 12 1/10 LED CURRENT (mA) 3/10 LED CURRENT vs. SUPPLY VOLTAGE LED CURRENT (mA) INPUT RIPPLE (mVRMS) 7 3.4 20 MAX1573 toc04 FULL 8 40 SUPPLY VOLTAGE (V) INPUT RIPPLE vs. SUPPLY VOLTAGE 9 60 0 3.0 3.5 3.4 3.0 FULL 20 LED CURRENT (mA) 4.2 3.9 80 MAX1573 toc06 EFFICIENCY (%) 3/10 100 BATTERY CURRENT (mA) 90 FULL 80 FULL 3/10 120 MAX1573 toc02 1/10 MAX1573 toc05 90 EFFICIENCY (%) 100 MAX1573 toc01 100 SUPPLY CURRENT vs. SUPPLY VOLTAGE 3.6V Li+ BATTERY INPUT MAX1573 toc09 3.4V Li+ BATTERY INPUT VIN 20mV/ div VIN 20mV/ div IIN 10mA/ div IIN 10mA/ div 20 FULL 15 3/10 10 1/10 5 20mV/ VOUT div VOUT 20mV/ div 0 5 6 7 8 9 10 11 12 13 14 15 500ns/div 500ns/div RSET (kΩ) _______________________________________________________________________________________ 3 MAX1573 Typical Operating Characteristics (VIN = 3.6V, EN1 = EN2 = IN, CIN = C1 = C2 = COUT = 1µF, RSET = 7.50kΩ, TA = +25°C, unless otherwise noted.) MAX1573 White LED 1x/1.5x Charge Pump in UCSP and Thin QFN Typical Operating Characteristics (continued) (VIN = 3.6V, EN1 = EN2 = IN, CIN = C1 = C2 = COUT = 1µF, RSET = 7.50kΩ, TA = +25°C, unless otherwise noted.) STARTUP AND SHUTDOWN RESPONSE DIMMING RESPONSE MAX1573 toc10 MAX1573 toc11 5V/ div VEN_ 2V/ div VENI1 50mA/ div IIN VOUT LED_ = 4 ✕ 17mA EN1 = EN2 2V/ div IOUT 50mA/ div EN2 = IN 500μs/div 5μs/div Pin Description PIN NAME FUNCTION TQFN UCSP 1 B2 C2P Transfer Capacitor 2 Positive Connection. See the Component Selection section for capacitor value. 2 A2 OUT Output. Bypass to GND with a 1µF ceramic capacitor. Connect to the anodes of all the LEDs. OUT is high impedance during shutdown. 3 A3 EN1 Enable, Dimming Control Input 1. EN1 and EN2 control shutdown and the LED current. See Table 1. 4 — N.C. No Connection 5 A4 EN2 Enable, Dimming Control Input 2. EN1 and EN2 control shutdown and the LED current. See Table 1. 6 B4 SET Bias-Current Set Input. Connect a resistor from SET to GND to set the LED bias current (ISET). ISET = 600mV/RSET. 7 C4 LED2 LED2 Cathode Connection and Charge-Pump Feedback. The charge pump regulates to the lowest voltage on any of the LED_ inputs. Connect LED2 to the cathode of one output LED. Connect LED2 to IN if this LED is not populated. 8 D4 LED1 LED1 Cathode Connection and Charge-Pump Feedback. The charge pump regulates to the lowest voltage on any of the LED_ inputs. Connect LED1 to the cathode of one output LED. Connect LED1 to IN if this LED is not populated. 9 C3 LED4 LED4 Cathode Connection and Charge-Pump Feedback. The charge pump regulates to the lowest voltage on any of the LED_ inputs. Connect LED4 to the cathode of one output LED. Connect LED4 to IN if this LED is not populated. 10 D3 LED3 LED3 Cathode Connection and Charge-Pump Feedback. The charge pump regulates to the lowest voltage on any of the LED_ inputs. Connect LED3 to the cathode of one output LED. Connect LED3 to IN if this LED is not populated. 11 D2 GND Ground 12 — N.C. No Connection 4 _______________________________________________________________________________________ White LED 1x/1.5x Charge Pump in UCSP and Thin QFN PIN NAME FUNCTION TQFN UCSP 13 D1 C1N Transfer Capacitor 1 Negative Connection. See the Component Selection section for capacitor value. 14 C1 IN Supply Voltage Input. IN supplies power for the IC. Bypass IN to GND with a 1µF ceramic capacitor. 15 B1 C2N Transfer Capacitor 2 Negative Connection. See the Component Selection section for capacitor value. 16 A1 C1P Transfer Capacitor 1 Positive Connection. See the Component Selection section for capacitor value. Block Diagram C1P C1N IN C2P C2N OUT 1x/1.5x REGULATED CHARGE PUMP The MAX1573 utilizes a proprietary 1x/1.5x fractional charge-pump topology to drive up to four white LEDs with regulated constant current for uniform intensity. The MAX1573 operates with a 1MHz fixed frequency. An external resistor (RSET) programs the full-scale LED current, while two digital inputs control on/off and provide brightness control. Output Regulation EN1 0.15V 1.25V BRIGHTNESS CONTROL 0.6V EN2 MINIMUM SELECT P P LDO CURRENT REGULATOR LED1 LDO CURRENT REGULATOR LED2 LDO CURRENT REGULATOR LED3 LDO CURRENT REGULATOR LED4 N SET The MAX1573 operates in 1x mode until just above dropout. Then the MAX1573 switches to 1.5x chargepump mode to regulate the lowest of LED1–LED4 to 150mV and maintain constant LED brightness even at very low battery voltages. Using this topology, there is no LED brightness change during the 1x/1.5x switchover, which guarantees no flicker on the display. The switchover scheme has low hysteresis, minimizing operation in the less-efficient 1.5x mode. The 1x mode produces almost no ripple, while the 1.5x mode regulates the output voltage by controlling the rate at which the transfer capacitors are charged. In this way, the switching frequency remains constant for reduced input ripple and stable noise spectrum. Soft-Start MAX1573 GND Detailed Description The MAX1573 is a complete charge-pump buck-boost converter requiring only four small ceramic capacitors. The MAX1573 includes soft-start circuitry to limit inrush current at turn-on. When starting up with an output voltage that is not near the input voltage, the output capacitor is charged directly from the input with a DACramped current source (with no charge-pump action) until the output voltage is near 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. In the case of 1.5x mode, soft-start operates until the lowest of LED1–LED4 reaches regulation. If an overload condition occurs, soft-start repeats every 2.1ms. If the output is shorted to ground, the output current is limited by the MAX1573 fractional-switching technique. _______________________________________________________________________________________ 5 MAX1573 Pin Description (continued) MAX1573 White LED 1x/1.5x Charge Pump in UCSP and Thin QFN True Shutdown™ Mode When EN1 and EN2 are grounded, the MAX1573 is in shutdown, and the charge pump examines whether the input voltage is greater than or less than the output voltage and shorts the transfer capacitor nodes to either IN or OUT as necessary. The output is high impedance in either case. Applications Information Dimming Using EN1 and EN2 Use EN1 and EN2 inputs as a digital 2-bit number to control on/off, 1/10, 3/10, and full current (see Table 1). RSET programs the full current level (see the Setting the Output Current section). Thermal Shutdown Dimming Using PWM into EN1 The MAX1573 includes a thermal-limit circuit that shuts down the IC at about +160°C. Turn-on occurs after the IC cools by approximately 20°C. Use EN2 for shutdown and drive EN1 with a PWM signal. Current can be varied from 1/10 to full. The waveforms in the Typical Operating Characteristics show the response time of dimming. EN2 keeps the part on, eliminating any soft-start delay that would impede PWM control, allowing a PWM frequency up to 50kHz (Figure 1). Setting the Output Current SET controls the LED bias current. Current flowing into LED1, LED2, LED3, and LED4 is a multiple of the current flowing out of SET. Set the output current as follows: ⎛ 0.6V ⎞ ILED _ = K x ⎜ ⎟ ⎝ RSET ⎠ where K = 22, 66, or 219 (depending upon EN1 and EN2, see Table 1), and RSET is the resistor connected between SET and GND (see the Typical Operating Circuit). Table 1. EN1/EN2 States EN1/EN2 STATES BRIGHTNESS LED CURRENT EN1 = low, EN2 = low Shutdown ILED = 0 EN1 = low, EN2 = high 1/10 Brightness ILED = 22 x ISET EN1 = high, EN2 = low 3/10 Brightness ILED = 66 x ISET EN1 = high, EN2 = high Full Brightness ILED = 219 x ISET Dimming Using a Filtered PWM Signal Use a high-frequency PWM signal to drive an R-C-R filter on the SET pin (Figure 2). A 0% PWM duty cycle corresponds to 18.7mA/LED, while a 100% PWM duty cycle corresponds to 0mA/LED. At PWM frequencies above 5kHz, C3 may be reduced. Input Ripple For LED drivers, input ripple is more important than output ripple. Input ripple depends on the source supply’s impedance. Adding a lowpass filter to the input further reduces input ripple. Figure 3 shows a C-R-C filter used to reduce input ripple to less than 2mVP-P when driving a 75mA load. Alternately, increasing CIN to 2.2µF or 4.7µF yields input ripple of 17mVP-P or 9mVP-P, respectively, with only a small increase in footprint. The 1x mode always has very low input ripple. True Shutdown is a trademark of Maxim Integrated Products, Inc. 1μF 1μF 1μF 1μF C1P C1N C2P C2N C1P C1N C2P C2N OUT IN VIN 1μF 1μF 1μF MAX1573 EN2 LED1 EN1 LED2 SET LED3 LED4 RSET GND Figure 1. Dimming Using PWM Signal into EN1 6 PWM INPUT 0 TO 2.5V R1 14.3kΩ C3 1μF R2 14.3kΩ 0 TO 18.7mA/LED 1μF MAX1573 PWM INPUT OUT IN VIN EN1 LED1 EN2 LED2 SET LED3 LED4 RSET 9.09kΩ GND Figure 2. Dimming Using Filtered PWM Signal _______________________________________________________________________________________ White LED 1x/1.5x Charge Pump in UCSP and Thin QFN Component Selection Use ceramic capacitors with an X5R dielectric or better temperature coefficient. The transfer capacitors may be reduced in value if the input voltage does not fall below 3.4V, if only two or three LEDs are used, or if four LEDs are used at 10mA or less. Some typical external component values are shown in Table 2. Under normal operating conditions, power dissipation is low. Maximum power dissipation occurs at an input voltage of 4.2V and all four LEDs (with VF = 4V) are driven with 30mA per LED. The power is calculated as: PD = [(1.5 x VIN) - VF] x 120mA = 276mW At higher input voltages, the MAX1573 switches to 1x mode and power dissipation decreases. Pin Configurations (continued) VIN 1Ω 1μF 1μF C1P C1N C2P C2N TOP VIEW OUT IN 1 2 3 4 C1P OUT EN1 EN2 C2N C2P A 1μF 2.2μF 2.2μF MAX1573 EN1 EN2 LED1 IN LED2 SET SET B LED4 LED2 LED3 LED1 C LED3 LED4 C1N RSET GND D GND UCSP 4 ✕ 4 Figure 3. C-R-C Filter Reduces Input Ripple Table 2. Typical Component Values COMPONENT Input/Output Capacitors Transfer Capacitors VALUE (µF) MANUFACTURER PART DESCRIPTION 1 Taiyo Yuden JMK107BJ105KA 1µF ±10%, 6.3V X5R ceramic capacitor (0603) 1 Taiyo Yuden JMK107BJ105KA 1µF ±10%, 6.3V X5R ceramic capacitor (0603) 0.47 Taiyo Yuden LMK107BJ474KA 0.47µF ±10%, 10V X5R ceramic capacitor (0603) 0.22 Taiyo Yuden LMK107BJ224KA 0.22µF ±10%, 10V X7R ceramic capacitor (0603) LED — Nichia NSCW215T RSET As required Panasonic — White LEDs ±1% resistor (0603) Chip Information TRANSISTOR COUNT: 3655 PROCESS: BiCMOS _______________________________________________________________________________________ 7 MAX1573 PC Board Layout and Routing The MAX1573 is a high-frequency switched-capacitor voltage regulator. For best circuit performance, use a solid ground plane and place CIN and COUT as close to the MAX1573 as possible. Also, place their ground pads close together and as close as possible to GND. See the MAX1573 EV kit for an example. 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. 24L QFN THIN.EPS MAX1573 White LED 1x/1.5x Charge Pump in UCSP and Thin QFN PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm 21-0139 E 1 2 PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm 21-0139 8 E 2 2 _______________________________________________________________________________________ White LED 1x/1.5x Charge Pump in UCSP and Thin QFN 16L,UCSP.EPS PACKAGE OUTLINE, 4x4 UCSP 21-0101 H 1 1 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 _____________________ 9 © 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc. MAX1573 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.
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