19-3117; Rev 0; 12/03 KIT ATION EVALU E L B AVAILA 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN 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). 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 0.1µA 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 Applications Ordering Information LCD Backlighting Camera Strobes/Flashes and Movie Lights Cell Phones/Smart Phones PART TEMP RANGE PINPACKAGE TOP MARK MAX1574ETB -40°C to +85°C 10 TDFN 3mm x 3mm ABB PDAs, Digital Cameras, and Camcorders Pin Configuration Typical Operating Circuit LED3 UP TO 180mA LED2 CN IN LED1 CP 2.7V TO 5.5V GND TOP VIEW OUT 0.22µF 10 9 8 7 6 OUT 1µF 1µF MAX1574 GND MAX1574 LED1 2 3 4 5 SET 1 CN LED3 IN SET LED2 CP EN EN ON/OFF AND DIMMING TDFN 3mm × 3mm ________________________________________________________________ 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 MAX1574 General 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 (1MHz) switching allows for tiny external components, and the regulation scheme is optimized to ensure low EMI and low input ripple. MAX1574 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN 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 = +70°C) 10-Pin TDFN (derate 18.2mW/°C above +70°C) .......1454mW 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 = 0V, EN = IN, RSET = 13.7kΩ, 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 VIN falling 2.25 Undervoltage-Lockout Hysteresis Output Overvoltage-Protection Threshold No-Load Supply Current Shutdown Supply Current 2.45 MAX UNITS 5.5 V 2.60 V 40 mV VOUT rising 5 V 2x mode 2 10% setting, 1x mode 0.35 EN = GND, TA = +25°C 0.01 EN = GND, TA = +85°C 0.1 Soft-Start Time mA 1 2 SET Bias Voltage SET Leakage in Shutdown TYP 2.7 ms 0.6 EN = GND, TA = +25°C 0.01 EN = GND, TA = +85°C 0.1 SET Current Range 4 µA V 1 153 µA µA SET-to-LED_ Current Ratio (ILED/ISET) 100% setting 393 A/A LED Current Accuracy TA = +25°C ±0.7 % LED-to-LED Current Matching (Note 2) -4 ±0.5 Maximum LED_ Sink Current RSET = 4.12kΩ 52 60 LED_ Dropout Voltage RSET = 4.12kΩ (Note 3) 1x to 2x Mode Transition Threshold VLED_ falling 120 Input-Voltage-Mode Transition Hysteresis LED Leakage in Shutdown Maximum OUT Current +4 80 120 130 140 150 EN = GND, TA = +25°C 0.01 EN = GND, TA = +85°C 0.1 VIN ≥ 3.12V, VOUT = 3.9V mV mV mV 2 180 µA mA 1.5 2.5 2x mode, (2 x VIN - VOUT) / IOUT 9 15 1 MHz OUT Pulldown Resistance in Shutdown EN = GND 5 kΩ EN High Voltage VIN = 2.7V to 5.5V EN Low Voltage VIN = 2.7V to 5.5V Open-Loop OUT Resistance 1x mode, (VIN - VOUT) / IOUT % mA Switching Frequency 2 1.6 _______________________________________________________________________________________ Ω V 0.4 V 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN (VIN = 3.6V, VGND = 0V, EN = IN, RSET = 13.7kΩ, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CONDITIONS EN Input Current TYP MAX EN = GND or 5.5V, TA = +25°C MIN 0.01 1 EN = GND or 5.5V, TA = +85°C 0.1 EN Low Shutdown Delay 1.0 EN tLO (Figure 1) 0.5 EN tHI (Figure 1) 2 UNITS µA 3.3 ms 500 µs 0.5 Initial EN tHI (Figure 1) Only required for first EN_ pulse µs 50 µs Thermal-Shutdown Threshold +160 °C Thermal-Shutdown Hysteresis 20 °C Note 1: Limits are 100% production tested at TA = +25°C. 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 = +25°C, unless otherwise noted.) INPUT CURRENT (mA) 70 60 50 40 30 ILED = 8mA ILED = 40mA ILED = 20mA ILED = 2mA 20 200 150 2.7 3.0 3.3 3.6 INPUT VOLTAGE (V) 3.9 20 ILED = 8mA 60mA/LED 15 2mA/LED 20mA/LED 10 8mA/LED 5 ILED = 2mA VIN FALLING 0 ILED = 20mA 100 50 10 VIN FALLING ILED = 40mA MAX1574 toc03 80 250 INPUT RIPPLE vs. SUPPLY VOLTAGE 25 INPUT RIPPLE (mVP-P) MAX1574 toc01 90 EFFICIENCY (%) INPUT CURRENT vs. INPUT VOLTAGE 300 MAX1574 toc02 EFFICIENCY vs. INPUT VOLTAGE 100 0 4.2 0 2.7 3.0 3.3 3.6 INPUT VOLTAGE (V) 3.9 4.2 2.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 3 MAX1574 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (Circuit of Figure 2, VIN = 3.6V, EN = IN, driving three white LEDs, TA = +25°C, unless otherwise noted.) LED CURRENT MATCHING vs. INPUT SUPPLY VOLTAGE LED CURRENT vs. TEMPERATURE 8.15 MAX1574 toc06 0.6 100 MAX1574 toc05 0.8 LED CURRENT vs. RSET 8.20 MAX1574 toc04 1.0 0.4 0.2 0 -0.2 -0.4 LED CURRENT (mA) 8.10 LED CURRENT (mA) LED CURRENT MATCHING (%) MAX1574 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN 8.05 8.00 7.95 10 7.90 -0.6 7.85 -0.8 ILED = 8mA -1.0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 7.80 -40 5.5 100% BRIGHTNESS SETTING 1 -15 10 35 60 85 1 10 TEMPERATURE (°C) INPUT SUPPLY VOLTAGE (V) 100 RSET (kΩ) OPERATING WAVEFORMS (1x) OPERATING WAVEFORMS (2x) MAX1574 toc07 MAX1574 toc08 VOUT 50mV/div AC-COUPLED VOUT 50mV/div AC-COUPLED VIN 20mV/div AC-COUPLED VIN 20mV/div AC-COUPLED IIN 50mA/div 50mA/div IIN 0mA 0mA 400ns/div 400ns/div STARTUP AND SHUTDOWN MAX1574 toc09 VEN 5V/div 100mA/div IIN 0mA VOUT 2V/div 0V 1ms/div 4 _______________________________________________________________________________________ 1000 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN DIMMING RESPONSE LINE TRANSIENT 3.8V TO 3.3V TO 3.8V MAX1574 toc10 VEN MAX1574 toc11 VIN 1V/div VOUT 1V/div IOUT 60mA, 20mA/div 2V/div IOUT 50mA/div VOUT 2V/div 10ms/div 100µs/div Pin Description PIN NAME FUNCTION 1 IN Supply Voltage Input. Connect a 0.47µF to 1µF ceramic capacitor from IN to GND. The input voltage range is 2.7V to 5.5V. IN is high impedance during shutdown. 2 EN 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 (50µs min) to set ILED to the maximum current (see the SETfunction). Pulse EN low for 0.5µs to 500µs to dim the LEDs (Figure 1). 3 CP Transfer-Capacitor Positive Connection. Connect a 0.22µF capacitor from CP to CN. 4 CN Transfer-Capacitor Negative Connection. Connect a 0.22µF capacitor from CP to CN. 5 SET Current-Set Input. Connect a resistor (RSET) from SET to GND to set the maximum LED current. ILED(MAX) = 393 × 0.6V / RSET. SET is internally biased to 0.6V. SET is high impedance during shutdown. 6 LED3 7 LED2 8 LED1 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. 9 GND Ground. Connect GND to system ground and as close as possible to the input-bypass capacitor ground. 10 OUT Output. Connect a 0.47µF to 1µF ceramic capacitor from OUT to GND, and connect OUT to the anodes of all the LEDs. OUT is pulled to ground through an internal 5kΩ resistor in shutdown. — EP Exposed Paddle. Connect the exposed paddle directly to GND underneath the IC. _______________________________________________________________________________________ 5 MAX1574 Typical Operating Characteristics (continued) (Circuit of Figure 2, VIN = 3.6V, EN = IN, driving three white LEDs, TA = +25°C, unless otherwise noted.) MAX1574 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN 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. 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. 0 INITIAL tHI ≥ 50µs 1 2 3 4 5 Setting the Output Current The LED current at full brightness is set by a resistor, RSET, as follows: RSET = 0.6V × 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 500µs 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. 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 5kΩ 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 +160°C. The part turns on after the IC cools by approximately 20°C. 6 7 8 9 10 11 EN tSOFT-START 100% ILED_ SHDN 90% 80% 70% tLO 500ns TO 500µs 60% 50% tHI 100% 90% ≥ 500ns 40% 30% 20% 10% 5% Figure 1. EN Timing Diagram 6 _______________________________________________________________________________________ tSHDN 2ms (typ) SHDN 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN MAX1574 Table 1. Recommended Components COMPONENT DESIGNATION VALUE CIN, COUT 1µF 0.22µF C1 0.47µF D1, D2, D3 — RSET As Required MANUFACTURER PART NUMBER DESCRIPTION Taiyo Yuden JMK107BJ105KA TDK C1005X5R0J105M 1µF ±10%, 6.3V X5R ceramic capacitors (0603) 1µF ±20%, 6.3V X5R ceramic capacitors (0402) Taiyo Yuden JMK105BJ224KV 0.22µF ±10%, 6.3V X5R ceramic capacitor (0402) TDK C1005X5R0J224K 0.22µF ±10%, 6.3V X5R ceramic capacitor (0402) Taiyo Yuden JMK105BJ474KV 0.47µF ±10%, 6.3V X5R ceramic capacitor (0402) TDK C1005X5R0J474K 0.47µF ±10%, 6.3V X5R ceramic capacitor (0402) Nichia NSCW215T Citizen CL-470S Kamaya Panasonic 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. 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 0.47µF. 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. — White LEDs White LED flash module 1% resistor 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 2.2µF cuts input ripple in half with only a small increase in footprint. The 1x mode always has very low input ripple. 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 MAX1574 180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN C1 0.22µF OR 0.47µF CP 2.7V TO 5.5V IN CN OUT 1x/2x REGULATING CHARGE PUMP CIN 1µF COUT 1µF ERROR AMP1 OVD CONTROL AND REFERENCE 0.18V 0.6V EN DIMMING CONTROL AND ENABLE ON OFF 1.25V SELMIN CONTROLLED-CURRENT MIRROR ERROR AMP2 LED1 D1 LED2 D2 LED3 D3 SET RSET MAX1574 GND Figure 2. Functional Diagram and Typical Application Circuit Chip Information 0.22µF CP 2.7V TO 5.5V TRANSISTOR COUNT: 6063 PROCESS: BiCMOS CN IN OUT 1µF 1µF MAX1574 GND LED1 ON/OFF AND DIMMING EN SET LED2 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 6, 8, &10L, DFN THIN.EPS L A D D2 A2 PIN 1 ID 1 N 1 C0.35 b E PIN 1 INDEX AREA [(N/2)-1] x e REF. E2 DETAIL A e k A1 CL CL L L e e A DALLAS SEMICONDUCTOR PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, 6, 8 & 10L, TDFN, EXPOSED PAD, 3x3x0.80 mm NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY APPROVAL DOCUMENT CONTROL NO. 21-0137 REV. D 1 2 COMMON DIMENSIONS SYMBOL A MIN. MAX. 0.70 0.80 D 2.90 3.10 E 2.90 3.10 A1 0.00 0.05 L k 0.20 0.40 0.25 MIN. A2 0.20 REF. PACKAGE VARIATIONS PKG. CODE N D2 E2 e JEDEC SPEC b T633-1 6 1.50±0.10 2.30±0.10 0.95 BSC MO229 / WEEA 0.40±0.05 1.90 REF T833-1 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF T1033-1 10 1.50±0.10 2.30±0.10 0.50 BSC MO229 / WEED-3 0.25±0.05 2.00 REF [(N/2)-1] x e DALLAS SEMICONDUCTOR PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, 6, 8 & 10L, TDFN, EXPOSED PAD, 3x3x0.80 mm APPROVAL DOCUMENT CONTROL NO. 21-0137 REV. 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 © 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX1574 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.)