FEATURES Ideal For White LED Driver Low Profile, Inductorless Regulator X. and X Modes for Highest Efficiency +.7V to +.V Input Voltage Range Fast Turn-On Time, 7µS ma Quiescent Current <.µa Shutdown Current Built-in 600kHz Oscillator Programmable Output Current or Voltage PWM Dimming Control with Enable Pin Shutdown to Disconnect Output from Input Soft Start to Eliminate In-Rush Current Industry Standard 0-pin MSOP Package and Small 0-pin DFN Package High Efficiency Charge Pump Regulator for White LEDs APPLICATIONS Next Generation Mobile Phones PDAs.V to.0v Conversion Digital Still Cameras Digital Camcorders Palmtop Computers Color LCD Modules DESCRIPTION The is a current regulated charge pump ideal for converting a Li-Ion battery input for driving white LED used in backlighting color displays. The charge pump automatically switches between X. and X modes based on the input voltage, providing improved efficiency over traditional methods using charge pump doubler followed by LDO. This input voltage threshold can be externally programmed for optimized efficiency at specific output voltages and currents. The operates with an internal 600kHz clock, enabling the use of small external components. Output current or voltage can be accurately regulated by modulating the switcher between the charge pump and output capacitor. In shutdown mode, the IC disconnects the output from the input and draws less than.µa current. The is offered in a 0-pin MSOP package, and a small 0-Pin DFN Package. TYPICAL APPLICATION SCHEMATIC CP 0 Pin DFN 0 CP 9 CN 7 CN 6 EN/PWM Now Available in Lead Free Packaging Lithium-Ion.7 -.V C.µF C.µF R CP CP CN CN EN/PWM 0 9 7 6 C6 0.µF C.µF C.µF White LED R C 0.µF R6 0 0 0 0 ENABLE/PWM DIMMING R M
,, and EN/PWM... -0.V to 6V -... 0.7V Output Current (I OUT )... 00mA Power Dissipation per Package - 0-pin MSOP (derate.mw/ C above +70 C)... 70mW Junction Temperature... + C Storage Temperature... -6 C to +0 C ESD Rating.... kv HBM ABSOLUTE MAXIMUM RATINGS These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. PARAMETER MIN TYP MAX UNITS CONDITIONS Input Voltage.7. V Quiescent Current. ma =.V, =.6V, I OUT = 00µA Shutdown Current. µa EN/PWM = 0V, =.V Oscillator Frequency 0. 0.60 0.7 MHz =.6V V Reference Voltage 0.7 0.06 0.7 V Charge Pump Output Ω = 0V, =.6V, Resistance I OUT = 0mA, = High Threshold Voltage... V Falling @ C Hysteresis for Mode Transition 0 mv PP =.6V @ C Voltage Pin Current 0.0 0. µa =. EN/PWM Logic Low 0. V EN/PWM Logic High.6 V EN/PWM Pin Current 0.0 0. µa V EN/PWM =.V Pin Current 0. µa V = V ELECTRICAL CHARACTERISTICS Unless otherwise specified: =+.7V to +.0V, C=C=C=C=.µF (ceramic, ESR=0.0Ω), C=0.µF (ceramic) and T AMB =-0 C to + C unless otherwise noted. Turn-On Time 7 00 µs =.6V, within 90% regulation
PIN NUMBER PIN NAME DESCRIPTION Regulated charge pump output. CP Positive terminal to the charge pump flying capacitor C. Input pin for the.7v to.v supply voltage. PIN DESCRIPTION Charge pump mode program pin. When is greater than.v, X. charge pump is used. Otherwise, charge pump switches to X mode. A voltage divider shown in typical application circuit programs the threshold for charge pump mode switching. This is the feedback pin for output current or voltage regulation. The voltage of this pin is compared with an internal 06mV reference. 6 EN/PWM Enable and PWM dimming control input. Pull this pin low to disconnect from and shutdown the. 7 CN Negative terminal to the charge pump flying capacitor, C. Ground reference. 9 CN Negative terminal to the charge pump flying capacitor, C. 0 CP Positive terminal to the charge pump flying capacitor C. FUNCTIONAL DIAGRAM EN/PW.V MODE COMP Voltage Referenc 600 khz Clock Manager Mode Control Start-up and Charge Pump Switches CP CN CP CN 06m COMP
PERFORMANCE CHARACTERISTICS Refer to the typical application circuit, T AMB = C, I O = 60mA unless otherwise specified. EN/PWM V/DIV 90 0 70 V/DIV Efficiency (%) 60 0 0 0 0 0 0.7..6.9. Input Voltage(V) Figure. Output voltage turn-on time Figure. Power efficiency vs. input voltage 0mV/DIV 0. 0. 0. 0. 0mV/DIV V (V) 0. 0.9 0. 0.7 0.6.7..6.9. (V) Figure. X mode voltage ripple when =.7V Figure. Feedback pin voltage vs. input voltage 0mV/DIV 0.9 0. 0.7 0mV/DIV I SUPPLY (ma) 0.6 0. 0. 0. 0. 0. 0.7..6.9. (V) Figure. X. mode voltage ripple when =.V Figure 6. Quiescent current vs. input voltage
PERFORMANCE CHARACTERISTICS: Continued Refer to the typical application circuit, T AMB = C, I O = 60mA unless otherwise specified. 6 00 Hz 00 Hz Brightness (kcd/m) Brigtness, kcd/m 0.7..6.9. Input Voltage (V) 0 0 0 0 60 0 00 Duty Cycle,% LED's @ 0mA LED's @ ma Figure 7. Brightness vs. input voltage Figure. Brightness vs duty cycle OPERATION General Overview The is a current regulated charge pump ideal for converting a Li-Ion battery input for driving white LEDs used in backlighting color displays in cellular phones, PDAs, digital cameras and MP players. The s proprietary AutoBoost feature enables the IC to automatically transition from X. boost mode to X boost mode based on battery input voltage for optimal efficiency and performance. The is able to efficiently drive up to six 0mA white LEDs in parallel and maintain a constant brightness over a very wide operating voltage range (.7V to.v). The operates with an internal 600kHz clock, enabling the use of small external components. Other features of include PWM dimming control as well as complete input/out disconnect in shutdown. In shut down mode the IC draws less than.µa current. The output regulation is achieved by sensing the voltage at the feedback pin and modulating the switcher between the charge pump and output capacitor. Theory of Operation The regulated charge pump block diagram consists of four main blocks (Voltage Reference, Mode Control, Clock Manager, Startup and Charge-Pump Switches) and two comparators ( Comparator and Comparator). ) Voltage Reference. This block provides the 06mV and.v reference voltages needed for the two comparators. ) Mode Control. An external voltage divider connected to the pin will define an input voltage to the mode comparator which sets the logic state of the mode selection outputs to the X or X. modes. is compared to a.v bandgap voltage. For example, if one makes a K/00K divider, the mode will change at. x. V =.V. A comparatorbased cycle by cycle regulation ensures that no mode change occurs during cycles. ) Clock Manager. An internal 600 khz clock is generated in this block. Depending on the mode control, the appropriate clock phasing is generated here and sent to the start-up and charge-pump switches block. ) Start-up and Charge Pump Switches. During start-up, until the reference is established, this block keeps the charge pump inactive. During this period the output stays floating, by consequence the charge pump drivers are now referenced to. Charging of the output will occur (e.g. when is ramped up to.v, ramps only up to about V), but not to the value of, protecting the White LED from experi-
encing high input voltages. Another important operation of this block is the PWM/EN dimming control, which is implemented in the delay of each pump driver, so that the enable high pulse width is proportional to the delay of the individual pump switches. ) Comparator and Output Control. A 06mV reference voltage is compared to feed- OPERATION: Continued back output voltage to control the Vout needed for the application. Output current is set by a bias resistor from pin to pin chosen by the relationship: I OUT = V R where V = 06mV. APPLICATION INFORMATION Configuring the as Voltage or Current Source The white LED load configuration used by customers can be discrete white LEDs or a white LED module. Inside the white LED module, there may or may not be resistors in series with the white LEDs. According to the different application requirements, the can be configured as either a voltage source or a current source to provide solutions for these different applications, as shown in figure 9~. Figure 9 shows using the to drive discrete white LEDs as a current source. The current in one white LED current is set by the ratio of the feedback pin voltage (06mV) and the bias resistor R B. To set the operating current, R B can be selected by: R B = V I LED The current of the remaining white LEDs is set according to the similarity of the white LEDs. - wire white LED module with internal series resistors as shown in figure 0 can also be driven in this way. Anode -wire W-LED module Fig 0. -wire white LED module In figure, was used to drive a -wire white LED module without internal series resistors as a current source. The bias resistor R B is selected to regulate the total current of the white LED module instead of the current of single LED as in figure 9. Anode -wire W-LED module.uf Rb Rb V Cathode Rb Figure 9. Driving discrete white LEDs as current source Figure. Driving -wire white LED module as current source 6
In this application, the bias resistor can be selected by: R B = V I LED (TOTAL) where I LED(TOTAL) is the total operating current of all the white LEDs. To use as a voltage source for fixed voltage applications, a voltage divider is need to program the ouput voltage, as shown in figure. The output voltage is set by the ratio of the two APPLICATION INFORMATION: Continued Programming the Operating Mode can automatically change from X. mode to X mode for highest efficiency. To use this feature, divider resistors should be chosen according to the specific application, as shown in figure. The guideline for divider resistor selections is as follows. For high input voltage, the will work in X. mode. When the input voltage drops to Vth threshold voltage, it will switch to X mode automatically. The Vth threshold voltage for mode change can be calculated by: Anode V TH = (V F + 0.06 + m I LED R OUT )/. V.uF R Where V F and m are the forward voltage and number of the white LEDs, Rout is the output resistance of the. R6 -wire W-LED module The equation for the voltage divider R and R with =.V is: Cathode V TH =.V (+R /R ) Figure. Driving -wire white LED module as voltage source resistors and the feedback control voltage as shown by: = ( + R ) V R 6 which can be expressed as R: R = (V TH /. -) R For the typical application, Using V F =.6V, m=, I LED =ma, R OUT =6Ω, the V TH will be.v. Select R =00kΩ, then R =kω. Capacitor Selection V IN R R C Figure. Programming the Vmode Resistors Ceramic capacitors are recommended for their inherently low ESR, which will help produce low peak to peak output ripple, and reduce high frequency spikes. The fly capacitor controls the strength of the charge pump. Selection of the fly capacitor is a trade-off between the output voltage ripple and the output current capability. Decreasing the fly capacitor will reduce the output voltage ripple because less charge will be delivered to the output capacitor. However, smaller fly capaci- 7
tor leads to larger output resistance, thus decreasing the output current capability and the circuit efficiency. Place all the capacitors as close to the as possible for layout. Increasing the value of the input and output capacitors could further reduce the input and output ripple. Refer to Table for some suggested low ESR capacitors. Table: SUGGESTED LOW ESR CAPACITORS MANUFACTURERS/ PART NUMBER CAPACITANCE/ CAPACITOR/ ESR TELEPHONE# VOLTAGE SIZE/TYPE AT 00kHz TDK/7-0-600 C0XRAK.µF/0V 00/XR 0.00Ω TDK/7-0-600 C0XR0J7K.7µF/6.V 00/XR 0.00Ω MURATA/770-6-00 GRMR60JKE0D.µF/6.V 060/XR 0.00Ω MURATA/770-6-00 GRM9R60J7KE0D.7µF/6.V 00/XR 0.00Ω Brightness Control Using PWM APPLICATION INFORMATION Dimming control can be achieved by applying a PWM control signal to the EN/PWM pin. The brightness of the white LEDs is controlled by increasing and decreasing the duty cycle of the PWM signal. While the operating frequency range of the PWM control is from 60Hz to 700Hz, the recommended maximum brightness frequency range of the PWM signal is from 60Hz to 00Hz. A repetition rate of at least 60Hz is required to prevent flicker. where I I are the operating current of the white LEDs,V F,V F are the forward voltage of the white LEDs. Since the brightness of the white LED is proportional to the operating current, for better brightness matching, a higher output voltage could be used. This could be done by using larger resistor, as shown in figure. Rb is used to bias the operating current of the white LED, Rb is use to increase the output voltage. Better brightness matching was achived at the cost of the power wasted on the bias resistor. Brightness Matching For white LEDs, the forward voltage drop is a function of the operating current. However, for a given current, the forward voltage drops do not always match due to normal manufacturing tolerance, thus causing uneven brightness of the white LEDs. In figure, assume high-precision bias resistors were used, the operating current ratio of two different branches can be easily derived as shown by: I V = OUT - V F I - V F V I I I n Rb Rb D VF Rb Rb D VF Figure. Increasing brightness matching Power Efficiency The efficiency of driving the white LEDs can be calculated by: η = V F I F V = F I F V F V i I i V i (n I F + I Q ) V i n Rb Dn VFn
APPLICATION INFORMATION Where V i, I i are input voltage and current V F, I F are the forward voltage and operating current of White LEDs I Q is quiescent current, which is considered small compared with I F. n is the boost ratio (X. or X) High Voltage White LED Driver The can also be configured as a high voltage boost converter to drive more than 0 white LEDs. Figure shows the schematic of this application as well as actual data showing efficiency of > %. By using an external inductor, MOSFET and diode, high output voltage can be generated to drive white LEDs ( branches, each branch has 6 white LEDs in series). The current through the white LEDs is determined by: I LED = V R L LQHCNR7M DS SCHOTTKY MBR00 ILED = V/R = 0mA 00.7uH D D D7 D 9 Vin:.7-.V C 0uF XR Ceramic EN/PWM 0 CP 9 CP CN 7 CN 6 EN/PWM R M Q SI0 SOT V.uF V C XR Ceramic D D D D6 D9 D0 D D Efficiency (%) 90 0 7 R R Figure. Using as a High Voltage White LED Driver 70.7.0..6.9. (V) PINOUTS CP 0 Pin DFN 0 9 7 6 CP CN CN EN/PWM CP 0 Pin MSOP 0 CP 9 CN 7 CN 6 EN 9
PACKAGE: 0 PIN MSOP D e Ø R E/ R E E Seating Plane Ø L L Gauge Plane Ø L e Pin # indentifier must be indicated within this shaded area (D/ * E/) B B 0 Pin MSOP JEDEC MO-7 (BA) Variation SYMBOL MIN NOM MAX A - -. A 0-0. A 0.7 0. 0.9 b 0.7-0.7 c 0.0-0. D E E e e L 0..00 BSC.90 BSC.00 BSC 0.0 BSC.00 BSC 0.6 0. L L N - 0.9 REF 0. BSC 0 - R 0.07 - - R 0.07 - - ø 0º - º ø 0º - º WITH PLATING c A b b A A Note: Dimensions in (mm) BASE METAL Section B-B 0
PACKAGE: 0 PIN DFN D D/ A E/ E Top View A A Side View x 0 Pin DFN JEDEC MO-9 (VEED-) VARIATION SYMBOL MIN NOM MAX A 0. 0.9 A 0 0.0 0.0 A 0. 0.6 0. A b 0. 0.0 REF 0. 0. D D..00 BSC.7 e E E. 0. PITCH.00 BSC -.7 K 0. - - L 0. 0. 0. Note: Dimensions in (mm) L K e D b E Bottom View
ORDERING INFORMATION Part Number Top Mark Operating Temperature Range Package Type EU...EU...-0 C to + C... 0 Pin MSOP EU/TR... EU...-0 C to + C... 0 Pin MSOP ER... EURYWW...-0 C to + C... 0 Pin DFN ER/TR... ERYWW...-0 C to + C... 0 Pin DFN Available in lead free packaging. To order add "-L" suffix to part number. Example: ER/TR = standard; ER-L/TR = lead free /TR = Tape and Reel Pack quantity is,00 for MSOP and,000 for DFN. CLICK HERE TO ORDER SAMPLES Corporation ANALOG EXCELLENCE Sipex Corporation Headquarters and Sales Office South Hillview Drive Milpitas, CA 90 TEL: (0) 9-700 FAX: (0) 9-7600 Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others.