TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 WHITE LED CHARGE PUMP CURRENT SOURCE WITH PWM BRIGHTNESS CONTROL FEATURES • • • • • • • • • • • Regulated Output Current With 0.3% Matching Over Temperature Drives up to 5 LEDs at 25 mA Each LED Brightness Control Through PWM Control Signal High Efficiency by Fractional Conversion With 1x and 1.5x Modes 1 MHz Switching Frequency 2.7 V to 6.5 V Operating Input Voltage Range Internal Softstart Limits Inrush Current Low Input Ripple and Low EMI Overcurrent and Overtemperature Protected Undervoltage Lockout With Hysteresis Ultra-Small 3mm x 3mm QFN Package APPLICATIONS • • White LED Backlight for Color Displays in Cellular Phones, Smart Phones, PDAs, Handheld PCs, Digital Cameras, and Camcorders Key Backlight DESCRIPTION The TPS60230 charge pump is optimized for white LED supplies in backlit color display applications. The device provides a constant current, set by an external resistor, for each LED. The supply voltage ranges from 2.7 V to 6.5 V and is ideally suited for all applications powered by a single LI-Ion battery cell or three to four NiCd, NiMH, or Alkaline battery cells. The TPS60230 provides up to 25 mA per LED, for a total of 125 mA, for input voltages ranging from 3.1 V to 6.5 V. High efficiency is achieved by utilizing a 1x/1.5x fractional conversion technique in combination with very low dropout current sources. Additionally, the current controlled charge pump ensures low input current ripple and EMI. Only two external 1 µF and two 0.47 µF capacitors are required to build a complete small and low cost power supply solution. The TP60230 switches at 1 MHz operating frequency and is available in a small 16-pin QFN (RGT) package to keep board space to a minimum. VIN = 2.7 V to 6.5 V VIN VOUT C1+ D1 C1− D2 0.47 F 1 F D3 0.47 F C2+ C2− 1 F D4 D5 EN1 EN2 GND ISET PGND Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2004, Texas Instruments Incorporated TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. ORDERING INFORMATION PACKAGED DEVICE (1) (2) PACKAGE MARKING TPS60230RGTR QFN BIZ (1) (2) T indicates shipment in tape and reel on a mini reel with 250 units per reel. R indicates shipment in tape and reel with 3000 units per reel. ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range (unless otherwise noted) (1) UNIT VI Supply voltage –0.3 V to 7 V Voltage at EN1, EN2, VOUT, ISET –0.3 V to VI Output current at VOUT 200 mA TJ Maximum junction temperature 150°C TA Operating free-air temperature –40°C to 85°C Tst Storage temperature –65°C to 150°C Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds (1) 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 under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. DISSIPATION RATINGS (1) (1) PACKAGE TA≤ 25°C POWER RATING DERATING FACTOR ABOVE TA = 25°C TA = 70°C POWER RATING TA = 85°C POWER RATING 16-Pin QFN (RGT) 1.9 W 20 mW/°C 1W 760 mW The thermal resistance junction to ambient of the QFN package is 52 °C/W. RECOMMENDED OPERATING CONDITIONS MIN TYP 6.5 UNIT Supply voltage at VIN 2.7 Maximum output current at VOUT 125 mA 1 µF Ci Input capacitor Co Output capacitor 0.47 1 Flying capacitor, C1, C2 0.22 0.47 Operating junction temperature 2 MAX -40 V µF µF 125 °C TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 ELECTRICAL CHARACTERISTICS VI = 3.6 V, EN1 = EN2 = VI, TA = -40°C to 85°C (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT SUPPLY VOLTAGE AND CURRENT VI Input voltage range IO = 0 mA to 75 mA 2.7 6.5 V VI = 4.2 V, x1-mode, EN1 = EN2 = 1, ISET = 20 µA 200 µA IO = 0 mA, x1.5-mode 2.1 mA EN2 = EN1 = GND 0.1 Overvoltage limit LED1 unconnected, VI = 4.2 V 5.5 V Startup time CO = 1 µF, IDX≥ 0.9 IDX, set 375 µs IQ Operating quiescent current ISD Shutdown current 1 µA CHARGE PUMP STAGE VOUT Softstart duration 160 f Switching frequency 0.75 η Efficiency VI = 3.7 V, ILED = 15 mA each, VDX = 3.1 V Shutdown temperature Temperature rising µs 1.25 MHz 83% °C 160 Shutdown temperature hysteresis Input current limit 1 EN2 = EN1 = 1, ISET = 100 µA 20 °C 350 mA CURRENT SINKS IDx Recommended maximum current per current sink 3.2 V ≤ VI≤ 6.5 V 25 mA IDx Current into each current sink when Iset is shorted to GND 3.0 V ≤ VI≤ 6.5 V, ISET shorted to GND 50 mA Current matching between any two outputs VDx = 3.1 V, TA = 25°C Line regulation 3.2 V ≤ VI≤ 6.5 V, VDx = 3.1 V, EN1 = EN2 = 1, ISET = 80 µA VISET Reference voltage for current set Iset Recommended ISET pin current range k IDx to Iset current ratio 200 EN2 = 1, EN1 = 0 400 Voltage at Dx to GND 580 600 4 EN2 = EN1 = 1, ISET = 80 µA 2% ±3% EN2 = 0, EN1 = 1 EN2 = 1, EN1 = 1 Vsource –2% 0.4% 230 mV 620 130 260 EN2 = 0, EN1 = 1 200 EN2 = 1, EN1 = 0 300 EN2 = 1, EN1 = 1 400 µA 280 mV ENABLE 1, ENABLE 2 VIH EN1, EN2 high level input voltage VIL EN1, EN2 low level input voltage 1.3 V 0.3 EN1, EN2 trip point hysteresis 50 V mV IIKG EN2 input leakage current EN1, EN2 = GND or EN2 = VI, VI = 6.5 V 0.01 1 µA II EN1 input current EN1 = VI, VI = 4.2 V 11 15 µA V(UVLO) Undervoltage lockout threshold Input voltage falling 2.1 V 50 mV Undervoltage lockout hysteresis Frequency range at PWM 0 Recommended ON-time for PWM signal Shutdown delay time 50 2.5 Delay time when EN1 = EN2 go to GND after which the TPS60230 shuts down completely 0.5 0.85 kHz µs 1.5 ms 3 TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 PIN ASSIGNMENT 12 13 11 C2+ C1+ C1− C2− QFN PACKAGE (TOP VIEW) 9 10 VOUT VIN 8 14 PGND GND 7 15 D1 EN1 6 16 D2 EN2 5 D3 4 D4 3 D5 2 ISET 1 Terminal Functions TERMINAL NAME NO. I/O DESCRIPTION C1+ 10 – Connect to the flying capacitor C1 C1– 11 – Connect to the flying capacitor C1 C2+ 9 – Connect to the flying capacitor C2 C2– 12 – Connect to the flying capacitor C2 D1-D5 6-2 I Current sink input. Connect the cathode of the white LEDs to these inputs. EN1 15 I Enable input. A logic high enables the converter, logic low forces the device into shutdown mode reducing the supply current to less than 1 µA if EN2 is tied to GND. EN2 16 I An applied PWM signal reduces the LED current as a function of the duty cycle of the PWM signal. EN1 and EN2 can be tied together for PWM dimming between 0 mA and the maximum set with ISET. EN1 and EN2 can also be used for digital dimming with 4 steps from 0 mA to the maximum current set with ISET. See the application section for more details. GND 14 – Analog ground ISET 1 I Connect a resistor between this pin and GND to set the maximum current through the LEDs. PGND 7 – Power ground, connect with analog ground (GND) VIN 13 I Supply voltage input VOUT 8 0 Connect the output capacitor and the anode of the LEDs to this pin. Power PAD – – Connect with PGND and GND 4 TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 FUNCTIONAL BLOCK DIAGRAM 1 F VOUT C1+ D5 0.47 F D4 Current Sinks C1− C2+ 0.47 F VIN Charge Pump D3 D2 D1 C2− 1 F Reference Control ISET EN1 EN2 RSET PGND GND 5 TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 TYPICAL CHARACTERISTICS Table of Graphs FIGURE vs Input voltage (ILED = 25 mA, 15 mA, 10 mA per LED), EN2 = 0, EN1 = 1, Show hysteresis (rising and falling VI), VLED = 3.1 V η Efficiency IQ No load quiescent current fs 1 vs Input voltage (ILED = 25 mA, 15 mA, 10 mA per LED), EN2 = 1, EN1 = 0, Show hysteresis (rising and falling VI), VLED = 3.1 V 2 vs Input voltage (ILED = 25 mA, 15 mA, 10 mA per LED), EN2 = EN1 = 1, Show hysteresis (rising and falling VI), VLED = 3.1 V 3 vs Input voltage (TA = –40°C, 25°C, 85°C) (measured with ID1 = 5 mA) 4 Maximum output current from charge pump stage vs Input voltage 5 Switching frequency vs Free-Air Temperature (TA = -40°C to 85°C, VI = 3.6 V) 6 LED current, ILED vs Duty cycle on PWM (ILED max set to 20 mA) For f = 32 kHz and f = 1 kHz, DC = 1% to 100%, VI = 3.6 V 7 Line transient response VI and ID1 vs time on scope, Show LED current at D1 with VI = 4.2 V to 3.6 V to 4.2 V with EN2 = EN1 = 11, 5x20 mA 8 Show PWM signal and current at D1 vs time on scope f = 32 kHz, VI = 3.6 V, duty cycle = 50%, EN1 = EN2 = PWM 9 Show PWM signal and current at D1 vs time on scope f = 1 kHz, VI = 3.6 V, duty cycle = 50%, EN1 = EN2 = PWM 10 VI = 3.6 V, 5x20 mA, EN1 = EN2 = 00 changed to EN2 = EN1 = 11 11 Dimming response Startup timing EFFICIENCY vs INPUT VOLTAGE EFFICIENCY vs INPUT VOLTAGE 100 90 80 ILED = 15 mA 80 70 ILED = 15 mA 70 Efficiency − % Efficiency − % ILED = 25 mA ILED = 25 mA 90 60 ILED = 10 mA 50 40 60 ILED = 10 mA 50 40 30 30 20 20 10 10 0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 VI − Input Voltage − V Figure 1. 6 5.9 6.3 6.5 0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 VI − Input Voltage − V Figure 2. 5.9 6.3 6.5 TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 EFFICIENCY vs INPUT VOLTAGE QUIESCENT CURRENT vs INPUT VOLTAGE 3 90 ILED = 25 mA 2.8 80 2.6 IQ− Quiescent Current − mA ILED = 15 mA Efficiency − % 70 60 50 ILED = 10 mA 40 30 TA = 25C 2 1.8 TA = −40C 1.6 1.4 TA = 85C 1.2 1 0.8 20 0.6 10 0.4 0.2 0 2.7 0 3.1 3.5 3.9 4.3 4.7 5.1 5.5 VI − Input Voltage − V 5.9 2.7 6.3 6.5 3.5 3.9 4.3 4.7 5.1 5.5 VI − Input Voltage − V Figure 4. MAXIMUM OUTPUT CURRENT vs INPUT VOLTAGE SWITCHING FREQUENCY vs FREE-AIR TEMPERATURE 5.9 6.3 6.5 1040 TA = 25C VI = 3.6 V VLED = 3.2 V 0.35 3.1 Figure 3. 0.40 1030 Switching Frequency − kHz I O(max) − Maximum Output Current − A 2.4 2.2 VLED = 3.4 V 0.30 VLED = 3 V 0.25 VLED = 3.6 V VLED = 3.8 V 0.20 0.15 0.10 1010 1000 990 0.05 0 2.7 1020 3.1 3.5 3.9 4.3 4.7 5.1 5.5 VI − Input Voltage − V Figure 5. 5.9 6.3 6.5 980 −40 −30 −20 −10 0 10 20 30 40 50 60 70 80 TA − Free-Air Temperature − C Figure 6. 7 TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 D1 LED CURRENT vs DUTY CYCLE LINE TRANSIENT 25 500 mV/div 20 f = 1 kHz EN1 = 1, EN2 = 1, VI = 3.6 V to 4.2 V, ILED = 20 mA, 5 LEDs Connected, ILED(D1) Measured With 1 Resistor, TA = 25C VI 3.6 V 15 f = 32 kHz 10 1 mA/div ILED(D1) − D1 LED Current − mA VI = 3.6 V, ILED max = 20 mA 5 ILED(D1) AC 0 0 10 20 30 40 50 60 70 Duty Cycle − % 80 90 100 100 s/div Figure 7. Figure 8. DIMMING RESPONSE DIMMING RESPONSE PWM 0V 2 V/div 2 V/div PWM 0V PWM Into EN1 and EN2, VI = 3.6 V, ILED = 20 mA, 5 LEDs Connected, f = 1 kHz, TA = 25C ILED(D1) 0A 10 mA/div 10 mA/div PWM Into EN1 and EN2, VI = 3.6 V, ILED = 20 mA, 5 LEDs Connected, f = 32 kHz, TA = 25C ILED(D1) 0A 5 s/div Figure 9. 8 200 s/div Figure 10. TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 5 V/div STARTUP TIMING EN1 + EN2 0V 1 V/div VOUT VI = 3.6 V, ILED = 20 mA, 5 LEDs Connected, TA = 25C 0V 100 mA/div II 0A 20 µs/div Figure 11. DETAILED DESCRIPTION OPERATION The TPS60230 uses a fractional conversion charge pump to generate a supply voltage for the integrated current sinks. These current sinks are used to ensure a constant current for each LED. Depending on the input voltage and programmed LED current, the charge pump either operates in the 1x mode or in the 1.5x mode. By switching automatically between these two modes, the circuit optimizes power conversion efficiency as well as extends operating time by allowing the discharge of the battery completely. The charge pump can generate 125 mA of output current, so each of the 5 LED outputs can be powered with up to 25 mA of current. The maximum LED current is set by a resistor connected to the ISET pin. This resistor programs a reference current, which is current mirrored to set the LED current. Applying a PWM signal to the EN1 pin and/or the EN2 pin controls the LED brightness. See a detailed description in the section Analog Dimming Using ISET Pin. LED CURRENT ADJUSTMENT (ISET) A resistor programs a reference current, which is current mirrored to set the LED current. The voltage at the ISET pin depends on the status of EN1 and EN2. The current in each LED is typically 260 times the current through the resistor at ISET. V R ISET k ISET I LED VISET— Voltage from ISET pin (0.2 V, 0.4 V or 0.6 V) to GND, see Table 1 ILED— Current per LED from Dx pin to GND k — ISET to Dx current ratio The LED current varies linearly from 0 mA to ILED(max) mA by applying a PMW signal with 0% to 100% duty cycle. The LED brightness can however also be controlled by an analog control signal that is fed into the ISET pin. 9 TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 DETAILED DESCRIPTION (continued) SOFT START The TPS60230 has an internal soft start circuit to limit the inrush current during startup. This prevents possible voltage drops of the input voltage if a high impedance power source is connected to the input of the TPS60230. When the device starts up with an output voltage that is below the input voltage, the output capacitor is charged directly from the input with a current source. The output current increases linearly until the output reaches within 300 mV of the input voltage. When the programmed output current can be reached with the 1x mode, the TPS60230 terminates the soft start and begins normal operation. When the desired output current cannot be reached, the charge pump begins operation in 1.5x mode and pumps the output voltage up to the needed level to reach the programmed output current. ENABLE (EN1, EN2) The enable pins EN1 and EN2 are used to enable the device or set it into shutdown. The TPS60230 is enabled if one of the enable pins is pulled higher than the enable trip point of 1.3 V. The device starts up by going through the soft start routine as described in the section Soft Start. Pulling both pins to GND, after a delay, programs the device to shutdown. In shutdown, the charge pump, current sources, voltage reference, oscillator, and all other functions are turned off and the supply current is reduced to 0.1 µA. EN1 and EN2 can also 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. This sets the current at the LEDs to be either the full current or a fraction of the full current. See Table 1 for further details. The maximum current through the LEDs is set by a resistor connected between ISET and GND. EN1 and EN2 can also be used for PWM dimming. The PWM signal can either be applied to EN1 or EN2, or both inputs can be tied together and the PWM signal can be applied to both pins. Depending on the configuration, the current during PWM dimming is switched between 0 mA and its maximum (EN1 and EN2 connected to the PWM signal) or between 0 mA 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 0 mA and 2/3 of the full range. Table 1. Enable Levels ENABLE LEVEL MODE LED CURRENT 0 SHUTDOWN 0 0 1 VISET = 200 mV 1/3 1 0 VISET = 400 mV 2/3 1 1 VISET = 600 mV Full EN2 EN1 0 UNDERVOLTAGE LOCKOUT The undervoltage lockout circuit shuts down the device when the voltage at VIN drops below a typical threshold of 2.15 V. This prevents damage to the device. The UVLO circuit allows the device to start up again after the voltage on the VIN pin has increased by about 100 mV above the UVLO lockout threshold. SHORT CIRCUIT AND OVERTEMPERTURE PROTECTION The current at the VOUT pin is limited typically to 250 mA. When the junction temperature exceeds 155°C, the device shuts down to protect the device from damage. After the temperature decreases to about 135°C, the device starts up again if it is enabled. OVERVOLTAGE PROTECTION AT VOUT The device uses the voltage at D1 to regulate voltage at VOUT. In case D1 is not connected, an overvoltage protection circuit ensures that the output voltage at VOUT does not exceed its limits. The connection of the LEDs must be started using D1 first. For all other LEDs there is no restriction in the sequence. For example, if there are only 3 LEDs used, the first LED is connected to D1 and the other two LEDs can be connected to any other of the D2 to D5 pins. 10 TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 THEORY OF OPERATION/DESIGN PROCEDURE Capacitor Selection Ceramic capacitors such as X5R or X7R are recommended to be used with the TPS60230. 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 2 lists capacitor types that have been tested with the TPS60230. Table 2. Capacitors PART VALUE VOLTAGE MANUFACTURER SIZE WEBSITE C1608X5R1A105M C1608X5R1A474M C2012X7R1C105M 1 µF 0.47 µF 1µ F 10 V 10 V 16 V TDK 0603 0603 0805 www.componnent.tdk.com LMK107BJ105MA LMK107BJ474MA LMK212BJ105MG 1 µF 0.47 µF 1µ F 10 V 10 V 10 V Taiyo Yuden 0603 0603 0805 www.t-yuden.com Power Efficiency The power conversion efficiency of the TPS60230 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 very 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. As the battery discharges further, the efficiency again increases until at about 3.1 V where it reaches a second maximum. Below 3.1 V input voltage, the maximum current per LED is less than 25 mA. Power Dissipation The maximum power dissipation inside the TPS60230 can be calculated based on the following equation: PD max = [(1.5 × VI) – VO + 0.4 V] × IO The maximum power dissipation occurs when the input voltage is just low enough to operate in 1.5x mode, with a forward voltage of the white LED at maximum. This is typically for VI = 4.2 V and a forward voltage of 3.6 V. This needs to be lower than the maximum allowed power dissipation of the package, which can be calculated using the following equation: T T A P Jmax D max, package T ja For example, the worst case power dissipation occurs at the input voltage level where the charge pump switches from the 1x mode to the 1.5x mode. At this operating point, the supply voltage to the current sources is at its maximum and the current sources must drop the most voltage in order to maintain a regulated output current. The worst case power dissipation occurs when all 5 LED outputs are fully loaded with 25 mA of LED current. • With: VI = 4.2 V, Vf = 3.6 V, IO = 125 mA (1.5x mode) • PD max = 0.39 W 11 TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 APPLICATION INFORMATION TYPICAL APPLICATION OF A SMART PHONE DISPLAY WITH RESISTORS CONNECTED IN PARALLEL If more than 25 mA of output current is needed, then the input pins to the current sinks can be connected in parallel as shown in the following application figure. This method can also be used to connect a LC display with only two connections for the white LEDs. VIN = 2.7 V to 6.5 V VIN VOUT C1+ D1 C1− D2 0.47 F 1 F D3 C2+ 0.47 F D4 D5 C2− 1 F EN1 ISET EN2 GND PGND Typical Smartphone Display Figure 12. Typical Application With Resistors in Parallel ANALOG DIMMING USING ISET PIN The ISET pin can be used to connect an analog dc signal in the range of 0 mV to 600 mV (EN1 = EN2 = 1) for analog dimming of the white LEDs. For an input voltage of 0 V at ISET, the current is at its maximum, whereas at 600 mV, the LED current is zero. The maximum current is: • For EN2 = EN1 = 1: ILED = Vset/Rset × K = 0.6V/6kR × 270 = 27 mA per LED • For EN2 = 1, EN0 = 1: ILED = Vset/Rset × K = 0.4V/6kR × 270 = 18 mA per LED • For EN2 = 0, EN1 = 1: ILED = Vset/Rset × K = 0.2V/6kR × 270 = 9 mA per LED • With EN2, EN1 set to 10 or 01, a voltage of 400 mV or 200 mV is required to set the LED current to zero. VIN = 2.7 V to 6.5 V VIN VOUT C1+ D1 C1− D2 0.47 F 1 F D3 0.47 F C2+ D4 D5 C2− 1 F EN1 EN2 ISET GND 6 k V = 0 mV to 600 mV PGND Figure 13. Analog Dimming Connections Using ISET Pin 12 TPS60230 www.ti.com SLVS516A – MAY 2004 – REVISED JUNE 2004 APPLICATION INFORMATION (continued) TYPICAL APPLICATION USING 2 WHITE LEDs AND 6 GREEN LEDs FOR LCD BACKLIGHT AND KEYBOARD LIGHTING The TPS60230 can be used to power any kind of LED. It is also possible to mix white LEDs with color LEDs which have a lower forward voltage. The LED with the highest forward voltage (typically the white LED) has to be connected to D1, because the output voltage of the charge pump is regulated in such a way to keep the voltage drop from D1 to GND at 400mV (with EN1 = EN2 = 1). Therefore the output voltage of the charge pump is regulated to: VOUT = VD1 + VFLEDD1 VOUT— Output voltage at VOUT VD1— Voltage from D1 to GND (Vsource at D1 pin, see electrical characteristics) VFLEDD1— Forward voltage of the LED connected to D1 Resistor Rg is used to provide current sharing between the 6 green LEDs. The upper value is calculated using: V V FLEDD1 Fg Rg Ig VFg— Forward voltage of a green LED Ig— Current per green LED VIN = 2.9 V to 6.5 V VIN VOUT C1+ D1 C1− D2 0.47 F 1 F 2 White LEDs With 30 mA Each D3 0.47 F 1 F C2+ D4 D5 C2− 6 Green LEDs With 5 mA Each EN1 EN2 ISET GND PGND 5.4 k Sets Current to 30 mA Per Current Sink (With EN2 = EN1 = 1) Figure 14. LED Connections for LCD Backlight and Keyboard Lighting PROPOSED LAND PATTERN FOR PCB PRODUCTION Refer to the application note SLUA271 for the proposed land pattern of the QFN package. PHOTO FLASH APPLICATIONS The TPS60230 can be used to power one or more white LEDs for photo flash applications. These applications usually require a certain current for a short period of time. The photo flash is typically turned on for 100 ms to 500 ms and turned off for a longer period of time. For such applications, when the TPS60230 is not turned on continuously, the device can support an output current of 150 mA. 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