芯美电子 EUP3674 Preliminary 3 Channel, 1X/1.5X Charge Pump White LED Driver DESCRIPTION FEATURES The EUP3674 is a high efficiency charge pump white LED driver. It supports 3 white LEDs with regulated constant current for uniform intensity. The EUP3674 maintains the highest efficiency by utilizing a 1.5X fractional charge pump and low dropout current regulators. User can easily configure each LED current up to 30mA by an external resistor. 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 6% by 16 steps. Once the desired brightness is set, the EUP3674 maintains constant LED current as long as EN is kept high. If EN is kept low for more than 2mS, the EUP3674 enters shutdown. The EUP3674 is available in a 12-pin 3mm x 3mm TDFN package. z z z z z z z z z z Up to 30mA Output Current for Each Channel Regulated IOUT with ± 0.4% LED Current Matching 1X/1.5X Modes for Ultra-High Efficiency 3V to 5.5V Input Voltage 1MHz Fixed Frequency Single-Wire Serial Pulse Interface to Set LED Current Soft Start Function Overvoltage Protection Thermal Shutdown Protection RoHS Compliant and 100% Lead(Pb)-Free APPLICATIONS z z Mobile phone Small LCD Backlighting Typical Application Circuit Figure 1. DS3674 Ver0.2 Oct. 2007 1 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 Preliminary EUP3674 Pin Configurations Package Type Pin Configurations TDFN-12 Pin Description PIN PIN 1 RSET 2 EN 3 C1P 4 C1N 5 VOUT 6 C2P 7 C2N 8 VIN 9 GND 10 LED1 11 LED2 12 LED3 DS3674 Ver0.2 Oct. 2007 DESCRIPTION Current-Set Input. Connect a resistor (RSET) from RSET to GND to set the maximum LED current. ILED(MAX) = 400 × 1.2V / RSET. RSET is internally biased to 1.2V. RSET 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 (25µs min) to set ILED to the maximum current (see the RSET function). Pulse EN low for 0.5µs to 500µs to dim the LEDs (Figure 3). Transfer-Capacitor Positive Connection. Connect a 1µF capacitor from C1P to C1N. Transfer-Capacitor Negative Connection. Connect a 1µF capacitor from C1P to C1N. Output. Connect a 1µF ceramic capacitor from OUT to GND, and connect OUT to the anodes of all the LEDs. There is no pull-down resistor from OUT to ground internal during shutdown. Transfer-Capacitor Positive Connection. Connect a 1µF capacitor from C2P to C2N. Transfer-Capacitor Negative Connection. Connect a 1µF capacitor from C2P to C2N. Supply Voltage Input. Connect a 1µF ceramic capacitor from IN to GND. The input voltage range is 3V to 5.5V. IN is high impedance during shutdown. Ground. Connect GND to system ground and as close as possible to the input-bypass capacitor ground. LEDx Cathode Connection. Current flowing into LEDx is based on RSET description above. Connect LEDx to VOUT for unused LEDs. LEDx is high impedance during shutdown. 2 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 Preliminary EUP3674 Ordering Information Order Number Package Type Marking Operating Temperature range EUP3674JIR1 TDFN-12 xxxxx P3674 -40 °C to 85°C EUP3674 □ □ □ □ Lead Free Code 1: Lead Free 0: Lead Packing R: Tape & Reel Operating temperature range I: Industry Standard Package Type J: TDFN Block Diagram Figure 2. DS3674 Ver0.2 Oct. 2007 3 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUP3674 Preliminary Absolute Maximum Ratings IN,OUT,EN to GND ------------------------------------------------------------ -0.3V to 6V SET,LED1,LED2,LED3,CN to GND------------------------------- -0.3V to (VIN+0.3V) VOUT to GND --------------------------------------------------------------- -0.3V to the greater of (VOUT+1V) or (VIN+1V) Junction Temperature -------------------------------------------------------------------- 150°C Lead Temperature ------------------------------------------------------------------------ 260°C Storage Temperature -------------------------------------------------------- -65°C to 150°C Operating Ratings Supply Voltage (VIN) ------------------------------------------------------------- 3V to 5.5V Operating Temperature ---------------------------------------------------------- -40°C to 85°C Thermal Resistance θJA (TDFN-12) ----------------------------------------------- 55°C/W Electrical Characteristics Unless otherwise specified, VIN=3.6V , VGND=0V , EN=VIN, RSET=20kΩ, TA= -40°C to 85°C, unless otherwise noted. Typical values are at TA=25°C. Parameter Conditions IN Operating Voltage Output Over voltage No-Load Supply Current Shutdown Leakage Current Min 3 5.8 1.5x mode 1.75 1x mode 0.4 EN=GND, TA=25℃ 0. 1 TA=25℃ LED-to-LED Current Matching Maximum LED Sink Current EN=GND, TA=25℃ Maximum OUT Current VIN ≥ 3.12V, VOUT=3.9V 1x mode ,( VIN-VOUT)/IOUT 1.5x mode, (1.5 × VIN-VOUT)/IOUT Switching Frequency EN High Voltage EN Low Voltage EN Input Current EN Low Shutdown Delay EN tLO (Figure 3.) EN tHI (Figure 3.) Intial EN tHI (Figure 3.) Thermal-Shutdown Threshold VIN = 3V to 5.5V VIN = 3V to 5.5V EN=GND or 5.5V, TA=25℃ Only required for first EN_pulse Thermal-shutdown Hysteresis DS3674 Ver0.2 Oct. 2007 V mA 1 µA 100 1.22 400 us V A/A ±4 % ± 0.4 % mA 0.1 1 90 µA mA 1.5 6.5 1 Ω 160 MHz V V µA ms µs µs µs ℃ 20 ℃ 1.6 1.4 0.5 0.5 25 Unit V 30 LED Leakage in Shutdown Open-Loop OUT Resistance Max. 5.5 Protection Threshold VOUT rising Soft-Start Time RSET Bias Voltage RSET to LED Current Ratio (ILED/ISET) 100% Setting LED Current Accuracy EUP3674 Typ 0.1 2 0.4 1 3 4 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUP3674 Preliminary Typical Operating Characteristics Input Current vs Input Voltage LED Efficiency vs Input Voltage 300 100% ILED=24mA 90% 250 ILED=15mA 80% ILED=9.5mA Input Current Efficiency 70% 60% 50% 40% ILED=24mA 30% ILED=15mA 20% ILED=9.5mA 10% ILED=4.15mA 200 ILED=4.15mA 150 100 50 0 0% 2.7 3.0 3.3 3.6 3.9 2.7 4.2 3.0 3.3 3.6 3.9 4.2 Power Supply (V) Input Voltage (V) L LED Current Matching vs Input Supply Voltage Input Rapple vs Supply Voltage 2.0% 40 1.6% LED Current Matching (%) Input Rapple (mVp-p) ILED=24mA ILED=15mA 30 ILED=9.5mA ILED=4.15mA 20 10 1.2% 0.8% 0.4% 0.0% -0.4% -0.8% -1.2% -1.6% -2.0% 0 3 2.7 3.2 3.7 Supply Voltage(V) 4.2 3.5 4 Input Supply Voltage (V) LED Current vs Set Resistor LED Current vs Set Resistor L E D C u rre n t (m A ) 100 10 1 1 DS3674 Ver0.2 10 Rset (KΩ) Oct. 2007 100 1000 5 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUP3674 Preliminary Typical Operating Characteristics (Continued) Operating Waveforms (1.5X) Operating Waveforms (1X) VOUT VOUT VIN VIN IIN IIN Dimming Response Start-Up and Shutdown VEN VEN IIN IIN VOUT DS3674 Ver0.2 Oct. 2007 6 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 Preliminary EUP3674 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. Detailed Description The EUP3674 charge pump drives up to three white LEDs with regulated constant current with uniform intensity. By utilizing adaptive 1.5x charge-pump modes and very-low-dropout current regulators, it achieves 90mA 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. Shutdown Mode When EN is held low for 2ms or longer, the EUP3674 is shut down and almost drop no current from power supply. Over-voltage Protection If any LED fails as an open circuit, the output voltage is limited to about 5.8V by gating on/off the charge pump. If any LEDx is floating or grounded, the EUP3674 operates in the same over-voltage protection mode. To avoid over-voltage protection mode when using fewer than three LEDs, connect any unused LEDx to VOUT (Figure 1). 1x to 1.5x Switchover When VIN is higher than the VF (LED Forward Conduct Voltage) of LED by 0.3V, EUP3674 operates in 1x mode and VOUT is pulled up to VIN. The internal current regulators regulate the LED current. As VIN drops, VLEDx also falls and cannot support the current user setting, the EUP3674 starts switching in 1.5x mode. When the input voltage rises above VF by 500mV, the EUP3674 switches back to 1x mode. Thermal Shutdown The EUP3674 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. Soft-Start Applications Information The EUP3674 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. If the output is shorted to ground, the output current is limited by the EUP3674 switching technique. Driving Fewer than Three LEDs When driving fewer than three LEDs, connect any unused LEDx directly to VOUT (Figure 1). When connected in this manner, the corresponding LED driver is disabled and consume no current from VOUT. 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. Setting the Output Current The LED current at full brightness is set by a resistor, RSET, as follows: R SET = 1.22V × 400 I LEDX Component Selection Use only ceramic capacitors with an X5R, X7R, or better dielectric. EN Dimming Control When the LEDs are enabled by driving EN high, the EUP3674 goes through soft-start, bringing the LED curent up to 100% LED current(ILED(MAX)) setting by RSET. Dimming is then done by pulsing EN low (500ns to 500us pulse width). Each pulse reduces the LED current by about 6.25%, so after one pulse the LED curent is 93.75% ILED(MAX). The fifteenth pulse reduces the current to 6.25%, so the LED current reduces from 100% ILED(MAX) to 6.25% ILED(MAX). The sixteenth pulse sets the LED current back to ILED(MAX). Figure 3 shows a timing diagram for EN, Figure 4 shows the LED Curent (Normalized) vs. EN Pulse Edges. DS3674 Ver0.2 Oct. 2007 PC Board Layout and Routing The EUP3674 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 EUP3674 as possible. 7 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 Preliminary EUP3674 Figure 3. EN Timing Diagram Figure 4. LED Current Control Profile DS3674 Ver0.2 Oct. 2007 8 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUP3674 Preliminary Packaging Information TDFN-12 SYMBOLS A A1 b E D D1 E1 e L DS3674 Ver0.2 Oct. 2007 MILLIMETERS MIN. MAX. 0.70 0.80 0.00 0.05 0.18 0.30 2.90 3.10 2.90 3.10 2.40 1.70 0.45 0.30 0.50 INCHES MIN. 0.028 0.000 0.007 0.114 0.114 MAX. 0.031 0.002 0.012 0.122 0.122 0.094 0.067 0.018 0.012 0.020 9 联系电话：１５９９９６４４５７９ ８３１５１７１５