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| 19-3117; Rev 0; 12/03 KIT ATION EVALU LE B AVAILA 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN General Description Features Up to 180mA (60mA/LED) Drive Capability 83% Average Efficiency (PLED / PBATT) Over Li+ Battery Discharge 0.5% (typ) LED Current Matching Adaptive 1x/2x Mode Switchover Low Input Ripple and EMI 5% to 100% Dimming Through Single-Wire Serial Pulse Interface Low 0.1A Shutdown Current 2.7V to 5.5V Supply Voltage Range Soft-Start Limits Inrush Current Output Overvoltage Protection Thermal-Shutdown Protection 10-Pin 3mm x 3mm TDFN Package MAX1574 The MAX1574 charge pump drives up to three white LEDs with regulated constant current for uniform intensity. By utilizing adaptive 1x/2x charge-pump modes and very-low-dropout current regulators, it achieves 180mA output drive capability and high efficiency over the 1-cell lithium-battery input voltage range. Fixed-frequency (1MHz) switching allows for tiny external components, and the regulation scheme is optimized to ensure low EMI and low input ripple. The MAX1574 uses an external resistor to set the fullscale 100% LED current. An enable input (EN) is used for simple on/off control or can be pulsed repeatedly to set lower LED current in multiple steps down to 5%. Once the desired brightness is set, the MAX1574 maintains constant LED current as long as EN is kept high. If EN is kept low for more than 2ms, the MAX1574 enters shutdown. The MAX1574 is available in a 10-pin 3mm x 3mm TDFN package (0.8mm max height). Applications LCD Backlighting Camera Strobes/Flashes and Movie Lights Cell Phones/Smart Phones PDAs, Digital Cameras, and Camcorders PART MAX1574ETB Ordering Information TEMP RANGE -40C to +85C PINPACKAGE 10 TDFN 3mm x 3mm TOP MARK ABB Typical Operating Circuit 0.22F GND OUT Pin Configuration LED1 LED2 7 4 CN TOP VIEW 2.7V TO 5.5V IN 1F CP CN OUT 1F UP TO 180mA 10 9 8 MAX1574 GND LED1 ON/OFF AND DIMMING EN MAX1574 LED2 1 IN 2 EN 3 CP 5 SET SET LED3 TDFN 3mm x 3mm ________________________________________________________________ Maxim Integrated Products LED3 6 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN MAX1574 ABSOLUTE MAXIMUM RATINGS IN, OUT, EN to GND..............................................-0.3V to +6.0V SET, LED1, LED2, LED3, CN to GND .........-0.3V to (VIN + 0.3V) CP to GND ......................................................................-0.3V to the greater of (VOUT + 1V) or (VIN + 1V) OUT Short Circuit to GND ..........................................Continuous Continuous Power Dissipation (TA = +70C) 10-Pin TDFN (derate 18.2mW/C above +70C) .......1454mW 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 = 0V, EN = IN, RSET = 13.7k, 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 Output Overvoltage-Protection Threshold No-Load Supply Current Shutdown Supply Current Soft-Start Time SET Bias Voltage SET Leakage in Shutdown SET Current Range SET-to-LED_ Current Ratio (ILED/ISET) LED Current Accuracy LED-to-LED Current Matching Maximum LED_ Sink Current LED_ Dropout Voltage 1x to 2x Mode Transition Threshold Input-Voltage-Mode Transition Hysteresis LED Leakage in Shutdown Maximum OUT Current Open-Loop OUT Resistance Switching Frequency OUT Pulldown Resistance in Shutdown EN High Voltage EN Low Voltage EN = GND VIN = 2.7V to 5.5V VIN = 2.7V to 5.5V 1.6 0.4 EN = GND, TA = +25C EN = GND, TA = +85C VIN 3.12V, VOUT = 3.9V 1x mode, (VIN - VOUT) / IOUT 2x mode, (2 x VIN - VOUT) / IOUT 180 1.5 9 1 5 2.5 15 100% setting TA = +25C (Note 2) RSET = 4.12k RSET = 4.12k (Note 3) VLED_ falling 120 -4 52 EN = GND, TA = +25C EN = GND, TA = +85C 4 393 0.7 0.5 60 80 130 150 0.01 0.1 2 120 140 +4 VOUT rising 2x mode 10% setting, 1x mode EN = GND, TA = +25C EN = GND, TA = +85C VIN falling CONDITIONS MIN 2.7 2.25 2.45 40 5 2 0.35 0.01 0.1 2 0.6 0.01 0.1 153 1 1 TYP MAX 5.5 2.60 UNITS V V mV V mA A ms V A A A/A % % mA mV mV mV A mA MHz k V V 2 _______________________________________________________________________________________ 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN ELECTRICAL CHARACTERISTICS (continued) (VIN = 3.6V, VGND = 0V, EN = IN, RSET = 13.7k, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER EN Input Current EN Low Shutdown Delay EN tLO (Figure 1) EN tHI (Figure 1) Initial EN tHI (Figure 1) Thermal-Shutdown Threshold Thermal-Shutdown Hysteresis Only required for first EN_ pulse CONDITIONS EN = GND or 5.5V, TA = +25C EN = GND or 5.5V, TA = +85C 1.0 0.5 0.5 50 +160 20 MIN TYP 0.01 0.1 2 3.3 500 MAX 1 UNITS A ms s s s C C MAX1574 Note 1: Limits are 100% production tested at TA = +25C. Limits over the operating temperature range are guaranteed by design. 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 LED_ drops 10% from the value at VLED_ = 0.2V. Typical Operating Characteristics (Circuit of Figure 2, VIN = 3.6V, EN = IN, driving three white LEDs, TA = +25C, unless otherwise noted.) EFFICIENCY vs. INPUT VOLTAGE MAX1574 toc01 INPUT CURRENT vs. INPUT VOLTAGE MAX1574 toc02 INPUT RIPPLE vs. SUPPLY VOLTAGE MAX1574 toc03 100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 2.7 3.0 3.3 3.6 INPUT VOLTAGE (V) VIN FALLING 3.9 ILED = 8mA ILED = 40mA ILED = 20mA ILED = 2mA 300 250 INPUT CURRENT (mA) 200 150 100 50 0 ILED = 8mA ILED = 2mA ILED = 40mA VIN FALLING 25 20 INPUT RIPPLE (mVP-P) 60mA/LED 15 2mA/LED 10 20mA/LED 8mA/LED ILED = 20mA 5 0 2.7 3.0 3.3 3.6 3.9 4.2 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V) SUPPLY VOLTAGE (V) 4.2 _______________________________________________________________________________________ 3 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN MAX1574 Typical Operating Characteristics (continued) (Circuit of Figure 2, VIN = 3.6V, EN = IN, driving three white LEDs, TA = +25C, unless otherwise noted.) LED CURRENT MATCHING vs. INPUT SUPPLY VOLTAGE 0.8 LED CURRENT MATCHING (%) 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 2.7 3.1 3.5 3.9 4.3 4.7 7.85 ILED = 8mA 5.1 5.5 7.80 -40 -15 10 35 60 85 TEMPERATURE (C) 1 1 100% BRIGHTNESS SETTING 10 RSET (k) 100 1000 MAX1574 toc04 LED CURRENT vs. TEMPERATURE MAX1574 toc05 LED CURRENT vs. RSET MAX1574 toc06 MAX1574 toc08 1.0 8.20 8.15 8.10 LED CURRENT (mA) 8.05 8.00 7.95 7.90 100 LED CURRENT (mA) 50mV/div AC-COUPLED 20mV/div AC-COUPLED 10 INPUT SUPPLY VOLTAGE (V) OPERATING WAVEFORMS (1x) MAX1574 toc07 OPERATING WAVEFORMS (2x) VOUT VOUT 50mV/div AC-COUPLED 20mV/div AC-COUPLED 50mA/div VIN VIN IIN IIN 50mA/div 0mA 400ns/div 400ns/div 0mA STARTUP AND SHUTDOWN MAX1574 toc09 VEN 5V/div IIN 100mA/div 0mA VOUT 2V/div 0V 1ms/div 4 _______________________________________________________________________________________ 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN Typical Operating Characteristics (continued) (Circuit of Figure 2, VIN = 3.6V, EN = IN, driving three white LEDs, TA = +25C, unless otherwise noted.) MAX1574 DIMMING RESPONSE MAX1574 toc10 LINE TRANSIENT 3.8V TO 3.3V TO 3.8V MAX1574 toc11 VIN VEN 2V/div 1V/div VOUT IOUT 50mA/div 1V/div VOUT 2V/div IOUT 60mA, 20mA/div 10ms/div 100s/div Pin Description PIN 1 NAME IN FUNCTION Supply Voltage Input. Connect a 0.47F to 1F ceramic capacitor from IN to GND. The input voltage range is 2.7V to 5.5V. IN is high impedance during shutdown. Enable and Dimming Control. Pulsing EN low dims the LEDs in multiple steps. Drive low for longer than 2ms (typ) to shut down the IC. From shutdown, drive EN high (50s min) to set ILED to the maximum current (see the SETfunction). Pulse EN low for 0.5s to 500s to dim the LEDs (Figure 1). Transfer-Capacitor Positive Connection. Connect a 0.22F capacitor from CP to CN. Transfer-Capacitor Negative Connection. Connect a 0.22F capacitor from CP to CN. Current-Set Input. Connect a resistor (RSET) from SET to GND to set the maximum LED current. ILED(MAX) = 393 x 0.6V / RSET. SET is internally biased to 0.6V. SET is high impedance during shutdown. LED_ Cathode Connection. Current flowing into LED_ is based on SET description above. In 2x mode, the charge pump regulates the lowest LED_ voltage to 0.18V. Connect LED_ to IN for unpopulated LEDs. LED_ is high impedance during shutdown. Ground. Connect GND to system ground and as close as possible to the input-bypass capacitor ground. Output. Connect a 0.47F to 1F ceramic capacitor from OUT to GND, and connect OUT to the anodes of all the LEDs. OUT is pulled to ground through an internal 5k resistor in shutdown. Exposed Paddle. Connect the exposed paddle directly to GND underneath the IC. 2 3 4 5 6 7 8 9 10 -- EN CP CN SET LED3 LED2 LED1 GND OUT EP _______________________________________________________________________________________ 5 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN MAX1574 Detailed Description The MAX1574 charge pump drives up to three white LEDs with regulated constant current for uniform intensity. By utilizing adaptive 1x/2x charge-pump modes and very-low-dropout current regulators, it achieves 180mA output drive capability and high efficiency over the 1-cell lithium-battery input voltage range. Fixed-frequency switching of 1MHz allows for tiny external components, and the regulation scheme is optimized to ensure low EMI and low input ripple. Setting the Output Current The LED current at full brightness is set by a resistor, RSET, as follows: RSET = 0.6V x 393 ILED _ EN Dimming Control When the LEDs are enabled by driving EN high, the MAX1574 goes through soft-start, bringing the LED current up to ILED_. Dimming is then done by pulsing EN low (500ns to 500s pulse width). Each pulse reduces the LED current by 10%, so after one pulse the LED current is 0.9 x ILED. The tenth pulse reduces the current by 5%, so the ILED_ current reduces from 0.1 x ILED_ to 0.05 x ILED. The eleventh pulse sets the LED current back to ILED_. Figure 1 shows a timing diagram for EN. If dimming control is not required, EN works as a simple on/off control. Drive EN high to enable the LEDs, or drive EN low for shutdown. 1x to 2x Switchover When VIN is higher than VOUT, the MAX1574 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 130mV, and the MAX1574 starts switching in 2x mode. When the input voltage rises above VOUT by approximately 50mV, the MAX1574 switches back to 1x mode. Soft-Start The MAX1574 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 2x 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 2x mode, soft-start operates until the lowest of LED1 to LED3 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 MAX1574 switching technique. Shutdown Mode When EN is held low for 2ms or longer, the MAX1574 is shut down and put in a low-current mode. OUT is internally pulled to GND with 5k during shutdown. Overvoltage Protection If any LED fails as an open circuit, the output voltage is limited to about 5V by gating on/off the charge pump. If any LED_ is floating or grounded, the MAX1574 operates in the same overvoltage-protection mode. To avoid overvoltage-protection mode when using fewer than three LEDs, connect any unused LED_ to IN (Figure 3). Thermal Shutdown The MAX1574 includes a thermal-limit circuit that shuts down the IC at approximately +160C. The part turns on after the IC cools by approximately 20C. 0 EN INITIAL tHI 50s 1 2 3 4 5 6 7 8 9 10 11 tSOFT-START 100% ILED_ SHDN 90% 80% 70% tLO 500ns TO 500s 60% 50% tHI 500ns 40% 30% 20% 10% 100% 90% 5% tSHDN 2ms (typ) SHDN Figure 1. EN Timing Diagram 6 _______________________________________________________________________________________ 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN MAX1574 Table 1. Recommended Components COMPONENT DESIGNATION CIN, COUT VALUE 1F 0.22F C1 0.47F D1, D2, D3 RSET -- As Required MANUFACTURER Taiyo Yuden TDK Taiyo Yuden TDK Taiyo Yuden TDK Nichia Citizen Kamaya Panasonic PART NUMBER JMK107BJ105KA C1005X5R0J105M JMK105BJ224KV C1005X5R0J224K JMK105BJ474KV C1005X5R0J474K NSCW215T CL-470S -- DESCRIPTION 1F 10%, 6.3V X5R ceramic capacitors (0603) 1F 20%, 6.3V X5R ceramic capacitors (0402) 0.22F 10%, 6.3V X5R ceramic capacitor (0402) 0.22F 10%, 6.3V X5R ceramic capacitor (0402) 0.47F 10%, 6.3V X5R ceramic capacitor (0402) 0.47F 10%, 6.3V X5R ceramic capacitor (0402) White LEDs White LED flash module 1% resistor Applications Information Driving Fewer than Three LEDs When driving fewer than three LEDs, connect any unused LED_ directly to IN (Figure 3). When connected in this manner, the corresponding LED driver is disabled. 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. Alternatively, increasing CIN to 2.2F cuts input ripple in half with only a small increase in footprint. The 1x mode always has very low input ripple. Driving Camera Strobes/Flashes The MAX1574's 180mA output capability makes it suitable for driving white LED camera strobes/flashes. For example, the typical operating circuit drives a 3-LED flash module with up to 60mA/LED. To ensure 180mA total drive capability at low input voltages, increase C1 to 0.47F. To drive fewer or more LEDs with regulated total current up to 180mA or to reduce the number of connecting wires, short LED1, LED2, and LED3 together. When connected this way, some LED modules have good LED-to-LED forward-voltage matching, while others may require individual ballast resistors. It is a good idea to keep the ballast resistance as low as practical for reasonable matching because high-ballast resistance reduces the output drive capability due to the higher VOUT requirement. Component Selection Use only ceramic capacitors with an X5R, X7R, or better dielectric. See Table 1 for a list of recommended parts. PC Board Layout and Routing The MAX1574 is a high-frequency switched-capacitor voltage regulator. For best circuit performance, use a solid ground plane and place CIN, COUT, and C1 as close to the MAX1574 as possible. Refer to the MAX1574 evaluation kit for an example. _______________________________________________________________________________________ 7 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN MAX1574 C1 0.22F OR 0.47F CP 2.7V TO 5.5V CIN 1F ERROR AMP1 IN CN OUT COUT 1F OVD 1x/2x REGULATING CHARGE PUMP DIMMING CONTROL AND ENABLE ON OFF EN CONTROL AND REFERENCE 0.18V 0.6V CONTROLLED-CURRENT MIRROR 1.25V SELMIN LED1 LED2 LED3 D1 D2 D3 ERROR AMP2 SET RSET MAX1574 GND Figure 2. Functional Diagram and Typical Application Circuit Chip Information 0.22F TRANSISTOR COUNT: 6063 PROCESS: BiCMOS OUT 1F 2.7V TO 5.5V IN 1F CP CN MAX1574 GND LED1 ON/OFF AND DIMMING EN LED2 SET LED3 Figure 3. Using the MAX1574 to Drive Fewer Than Three LEDs 8 _______________________________________________________________________________________ 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN 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.) 6, 8, &10L, DFN THIN.EPS MAX1574 L D A A2 PIN 1 ID D2 1 N 1 b PIN 1 INDEX AREA C0.35 [(N/2)-1] x e REF. e E DETAIL A E2 A1 k C L C L L e A e L SEMICONDUCTOR PROPRIETARY INFORMATION TITLE: DALLAS PACKAGE OUTLINE, 6, 8 & 10L, TDFN, EXPOSED PAD, 3x3x0.80 mm NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY APPROVAL DOCUMENT CONTROL NO. REV. 21-0137 D 1 2 COMMON DIMENSIONS SYMBOL A D E A1 L k A2 MIN. 0.70 2.90 2.90 0.00 0.20 MAX. 0.80 3.10 3.10 0.05 0.40 0.25 MIN. 0.20 REF. PACKAGE VARIATIONS PKG. CODE T633-1 T833-1 T1033-1 N 6 8 10 D2 1.500.10 1.500.10 1.500.10 E2 2.300.10 2.300.10 2.300.10 e 0.95 BSC 0.65 BSC 0.50 BSC JEDEC SPEC MO229 / WEEA MO229 / WEEC MO229 / WEED-3 b 0.400.05 0.300.05 0.250.05 [(N/2)-1] x e 1.90 REF 1.95 REF 2.00 REF SEMICONDUCTOR PROPRIETARY INFORMATION TITLE: DALLAS PACKAGE OUTLINE, 6, 8 & 10L, TDFN, EXPOSED PAD, 3x3x0.80 mm APPROVAL DOCUMENT CONTROL NO. REV. 21-0137 D 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. |
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