Preliminary YB1315 High Efficiency Charge Pump White LED Driver Description Features The YB1315 charge pump is designed to drive up to 5 white LEDs with regulated constant current in backlight display application. The device can provide up to 25mA per LED for a total 5 channels. The output current can also be combined into one single channel with 125mA output current for flash-light applications. The input voltage ranges from 2.7V to 5.5V and is ideal for applications powered by a single Li-Ion or 3 to 4 NiCd, NiMH or Alkaline batteries. Voltage Input Range From 2.7V to 5.5V YB1315 monitors the power-supply input voltage and LED forward voltage and current, and does an automatic selection to a switching mode that is optimized for the power conversion efficiency as well as battery operating time. The 1MHz fixed frequency switching allows for tiny external components, and the regulation scheme is optimized to ensure low EMI and low input ripple. Internal soft-start circuitry effectively reduces the in-rush current. YB1315 also provides short circuit protection, over-temperature protection and over-voltage protection. In shutdown mode, the shutdown current is less than 1μA. YB1315 is available in a TQFN-16 3x3 package. Drives From 3 to 5 LEDs at Up to 25mA Each Fractional Conversion Modes for High Conversion Efficiency, 1x and 1.5x 1MHz Internal Oscillator Thermal Protection Shutdown Output Short-circuit Current Limit and Over-Voltage Protection Under-Voltage Lockout with Hysteresis Automatic Soft-Start Reduces In-Rush Current 3mm x 3mm TQFN Package Applications White LED Backlighting Handheld PCs and PDAs Mobile Phone DSC and DV flash light application Typical Application Circuit VIN = 2.7V to 5.5V VIN VOUT C1+ D1 C1- D2 1uF 0. 47 µF C2+ 0. 47 µF C2- YB1315 D3 D4 D5 EN1 1µF EN2 ISET GND PGND Figure 1: Typical Application Circuit YB1315 Rev.0.1 www.yobon.com.tw 1 Preliminary YB1315 GND C1+ 10 9 8 14 7 15 6 16 3 5 4 VOUT PGND D1 D2 D3 2 ISET 1 D4 EN2 11 D5 EN1 12 13 VIN C1- C2- Pin Configuration C2+ High Efficiency Charge Pump White LED Driver TQFN-16 3x3 Figure 2: Pin Configuration Pin Description Table 1 Pin Name Description 1 ISET Connect a RSET resistor between this pin and GND. RSET=7.5K, set ILED to 20mA. (Recommended) 2 D5 Current sink output #5. If not used, connected to VIN or floating. 3 D4 Current sink output #4. If not used, connected to VIN or floating. 4 D3 Current sink output #3. If not used, connected to VIN or floating. 5 D2 Current sink output #2. If not used, connected to VIN or floating. 6 D1 Current sink output #1. If not used, connected to VIN or floating. 7 PGND 8 VOUT Charge pump output. 9 C2+ Flying capacitor 2 positive terminal. Connect a 0.47μF capacitor between C2+ and C2-. 10 C1+ Flying capacitor 1 positive terminal. Connect a 0.47μF capacitor between C1+ and C1-. 11 C1- Flying capacitor 1 negative terminal. 12 C2- Flying capacitor 2 negative terminal. 13 VIN Input voltage. 14 GND Analog GND. 15 EN1 Enable input1. 16 EN2 Enable input2. EN1 and EN2 can be used for digital dimming with 4 steps from 0mA to the maximum current set with ISET. Power GND. Ordering Information Table 2 Order Number Package Type Supplied As Package Marking YB1315A316 TQFN-16 3x3 2500 Units Tape & Reel Please contact sales representative YB1315 Rev.0.1 www.yobon.com.tw 2 Preliminary YB1315 High Efficiency Charge Pump White LED Driver Absolute Maximum Ratings Recommended Operating Conditions Supply Voltage.......................................5.5V Output Short-Circuit Duration...... Continuous Junction Temperature Range...............150℃ Storage Temperature Range.. -65℃ to 150℃ Lead Temperature................................250℃ Input Supply Voltage............... 2.7V to 5.5V Operating Temperature..........-40℃ to 85℃ Electrical Characteristics Table 3 (VIN=3.6V, EN1=EN2=VIN, TA=25°C, unless otherwise noted.) Description Symbol Test Conditions SUPPLY VOLTAGE AND CURRENT Input Voltage Range VIN IOUT = 0~70mA Operating Quiescent Current IQ VIN =4.2V, x1-mode, EN1=EN2=1, ISET =20μA Shutdown Current ISD EN1=EN2=GND MIN TYP 2.7 MAX Units 5.5 V 250 μA 2 IOUT = 0mA, x1.5-mode 0.1 mA 1 μA CHARGE PUMP STAGE Over Voltage Limit VOUT Startup Time LED1 unconnected, VIN =4.2V 5.3 V COUT =1μF, IDX ≥0.9IDX 750 μs 500 Softstart Duration Switching Frequency f Efficiency η 0.7 VIN =3.75V, ILED=20mA each VDX =3.2V 1 μs 1.3 MHz 83 % Shutdown Temperature 160 ℃ Shutdown Temperature Hysteresis 20 ℃ 25 mA CURRENT SINKS Recommended Maximum Current Per Current Sink IDX 3.2V≤VIN≤5.5V Current into Each Current Sink when ISET is Shorted to GND IDX 3.0V≤VIN≤5.5V ISET short to GND 60 mA Current Matching Between Any Two Outputs VDX =3.2V, TA =25℃ ±3 % Line Regulation 3.2V≤VIN≤5.5V, VDX =3.2V EN1=EN2=1, ISET =80μA ±3 % 200 EN2=0, EN1=1 Reference Voltage for Current Set Recommended ISET Pin Current Range IDX to ISET Current Ratio Voltage at Dx to GND YB1315 Rev.0.1 VISET EN2=1, EN1=1 580 EN2=1, EN1=1, ISET =80μA 220 ISET k 600 620 250 280 4 VSOURCE www.yobon.com.tw mV 400 EN2=1, EN1=0 100 0.4 μA V 3 Preliminary YB1315 High Efficiency Charge Pump White LED Driver ENABLE 1, ENABLE 2 EN1, EN2 High Level Input Voltage VIH EN1, EN2 Low Level Input Voltage VIL Supply voltage falling 1.3 50 EN1, EN2 Trip Point Hysteresis EN2 Input Leakage Current EN1 Input Current Under Voltage Lockout Threshold V 0.3 0.1 1 μA II 0.1 1 μA V(UVLO) 2.1 Input voltage falling V 50 mV 50 Frequency Range at PWM Recommended ON-Time for PWM Signal YB1315 Rev.0.1 mV IIKG Under Voltage Lockout Hysteresis Shutdown Delay Time V 2.5 Delay time when EN1=EN2 go to GND after which the YB1315 shuts down completely. www.yobon.com.tw 0.5 1 KHz μs 1.5 ms 4 Preliminary YB1315 High Efficiency Charge Pump White LED Driver Typical Performance Characteristics VIN =3.6V, CIN =4.7μF, C1=C2=0.47μF, COUT = 1μF, unless otherwise noted. Dimming Response Efficiency vs. Supply Voltage (ILED=20mA) LED Efficiency VIN=3.6V, ILED=20mA 5 LEDs connected, f= 1k Hz 90 80 ILED1 DC Coupled 20mA/Div Efficiency (%) 70 60 50 40 30 EN2/EN1 DC Coupled 2V/Div 20 10 0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Time=500μs/div VI (V) 1X Mode, Software Dimming Respons VEN2/VEN1 DC Coupled 5V/Div VIN=3.6V, ILED=20mA 5 LEDs connected, f= 32k Hz ILED1 DC Coupled 20mA/Div VOUT DC Coupled 2V/Div EN2/EN1 DC Coupled 2V/Div IIN DC Coupled 200mA/Div Time=100μs/div Time=500μs/div Input and Output Voltage Ripple LED1 Current VS Duty Cycle VIN AC Coupled 50mV/Div 18 16 VOUT AC Coupled 50mV/Div L E D1 C ur r e nt ( m A) 14 VIN=3.4V, 1.5X ILED1=20mA 5LEDs connected 12 10 8 6 4 2 0 0 Time=1μs/div YB1315 Rev.0.1 10 20 30 40 50 60 70 80 90 Duty C yc le ( % ) www.yobon.com.tw 5 Preliminary YB1315 High Efficiency Charge Pump White LED Driver Function Block C1+ 10 C1- 11 C2+ 9 C2- 12 VIN 13 PGND VOUT 7 8 Current Sinks 1x/1.5x Charge Pump 2 D5 3 D4 4 D3 5 D2 6 D1 1 ISET Reference UVLO Control EN1 15 OVP EN2 16 14 GND Figure 3: Function Block Functional Description The YB1315 uses a multi-mode fractional charge pump to generate a supply voltage and a precise sink circuitry to ensure a constant driving current for each LED. The charge pump operates in either 1x mode, or 1.5x mode, depending on the input voltage and output current loading. The overall power consumption is best optimized by automatically switching among the 2 different operation mode. YB1315 Rev.0.1 The charge pump is possible to generate a total output current of 125mA or more, 25mA for each LED. But it is recommended to operate the device under total 120mA. www.yobon.com.tw 6 Preliminary YB1315 High Efficiency Charge Pump White LED Driver Application Information Soft-Start Circuitry The YB1315 includes soft-start circuitry to limit inrush current at turn-on. Once the input voltage is applied, 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. In the case of 1.5x mode, soft-start operated until the lowest of LED1-LED5 reaches regulation. ENABLE (EN1, EN2) The enable pins EN1 and EN2 are used to enable or shutdown the device. The YB1315 is enabled if one of the enable pins is pulled higher than the enable trip point of 1.2V. The device starts up by going through the soft start routine as described above. Pulling both pins to GND, after a delay, forces the device into to shutdown mode. In shutdown, the charge pump, current sources, voltage reference, oscillator, and all other functions are turned off and the supply current is reduced to 0.1μA. Methods for Dimming Control YB1315 offers flexible ways for dimming control. 1. EN1 and EN2 can be used for dimming. The logic levels at EN1 and EN2 set the minimum voltage at the current mirrors and the voltage at the ISET pin to GND. YB1315 Rev.0.1 This sets the current at the LEDs to be either the full current or a fraction of the full current. See Table 4 for further details. The maximum current through the LEDs is set by a resistor connected between ISET and GND described later. Table 4. Enable Levels Enable Level MODE EN2 EN1 LED Current 0 0 Shutdown 0 0 1 VISET=200mV 1/3 1 0 VISET=400mV 2/3 1 1 VISET=600mV Full 2. EN1 and EN2 can also be used for PWM dimming. The LED brightness level is directly dependent on the duty cycle of the PWM signal and the configuration. The PWM signal can either be applied to EN1 or EN2, or both tied together, and the PWM signal can be applied to both pins. Depending on the configuration, the current during PWM dimming is switched between 0mA and its maximum (EN1 and EN2 connected to the PWM signal) or between 0mA and 1/3 of the full LED current if EN2= 0 and EN1 is toggled. When EN1 = 0 and EN2 is toggled, the output current can be changed between 0mA and 2/3 of the full range. LED Current Setting The current of white LED connected to YB1315 can be set by RSET. Every current flow through the white LED is 250 times www.yobon.com.tw 7 Preliminary YB1315 High Efficiency Charge Pump White LED Driver greater than the current through that of RSET. The white LED can be estimated by following equation: ⎛V ⎞ I LED = 250 × ⎜ ISET ⎟ ⎝ RSET ⎠ To set the LED current, the device uses a RSET resistor connected the pin ISET to ground to generate a reference current VISET/RSET , where VISET is the voltage from ISET pin to ground. This reference current is amplified by K (250 typical) to generate the LED current. Following table shows the relation between RSET and LED current. Rset (KΩ) Iled (mA) 6 25 7.5 20 10 15 15 10 150 1 Thermal Protection The regulator has thermal shutdown circuitry that protects it from damage caused by high temperature conditions. The thermal protection circuitry shut down the device when the junction temperature reached approximately 160℃, allowing the device to cool. When the junction temperature cools to approximately 140℃, the device is automatically re-enabled. Continuously running the regulator into thermal shutdown can degrade reliability. Under-voltage Lockout The under-voltage lockout circuit shuts down the device when the voltage at VIN drops below a typical threshold of 2.2V. This prevents damage to the devices. YB1315 Rev.0.1 Power Efficiency The battery current and efficiency of the YB1315 are mostly dependent on the charge pump mode of operation. To get the best performance from the YB1315 it is better to use LEDs with consistently lower VF voltage. Lower VF will keep the charge pump in 1x mode longer and will uses less battery current, extending the run time of the battery. The power conversion efficiency of the YB1315 can be calculated by adding up the products of each LED current and voltage and dividing it by the product of the input voltage and current. With a fully charged battery where the input voltage is typically above the LED forward voltage, the charge pump operates in the 1x mode and efficiency is high. As the battery discharges, there is a point where the current sources no longer have enough voltage overhead to maintain a constant current regulation. At that point, the charge pump switches into the 1.5x mode. The conversion efficiency is lowest at the crossover. When in 1x mode the voltage conversion efficiency is defined as output power divided by input power: η= POUT VOUT × I OUT = × 100% PIN VIN × I IN I IN = I OUT + I Q η= POUT VOUT × I OUT = × 100% PIN VIN × ( I OUT + I Q ) When in 1.5x mode the voltage conversion efficiency is as output power divided by input power: www.yobon.com.tw 8 Preliminary YB1315 High Efficiency Charge Pump White LED Driver η= POUT VOUT × I OUT = ×100% PIN VIN × I IN I IN = I OUT + I Q η= POUT VOUT × I OUT = ×100% PIN VIN × ( I OUT × Mode + I Q ) Mode = 1.5 And then LEDs efficiency is defined as LED forward voltage produces output current divided by input power: η= POUT VF × I OUT = ×100% PIN VIN × ( I OUT × Mode + I Q ) Capacitor Selection Ceramic capacitors such as X5R or X7R are recommended to be used with the YB1315. For the two flying capacitors C1 and C2, it is important to use low ESR capacitors to avoid unnecessary efficiency losses. Low ESR capacitors on VOUT reduce the ripple voltage on the supply of the current sources. Table 5 lists capacitor types that have been tested with the YB1315. Table 5. Recommended Capacitors and WLED Part Value Voltage Manufacturer Size Website C1608X5R1A105KT000E C1608X7R1A105KT0S0N C2012X7R1C225KT000N 1μF 1μF 2.2μF 10V 10V 16V TDK 0603 0805 0805 www.component.tdk.com ECJ1VB1A105K ECJ2FB1A105K ECJ2FB1A225K 1μF 1μF 2.2μF 10V 10V 16V Panasonic 0603 0805 0805 www.panasonic.com LTW-193TS5 － － Lite-On － www.liteon.com.tw YB1315 Rev.0.1 www.yobon.com.tw 9 Preliminary YB1315 High Efficiency Charge Pump White LED Driver Package Information (TQFN-16 3x3) NOTICE: y The information described herein is subject to change without notice. y Yobon does not assume any responsibility for use of any circuitry or applications described herein, nor does it convey any patent license. YB1315 Rev.0.1 www.yobon.com.tw 10