PAM2701

PAM2701 4-Channel Regulated Charge Pump White LED Driver F eatures n n n n n n n n n n n Description The PAM2701 is a 4-channel charge pump white LED driver, capable of driving up to 4 LEDs in parallel. The device operates in either 1x mode or 1.5x fractional mode, and it can switch from 1x mode to 1.5x mode automatically when the input voltage decreased. Its internal 4 current sink regulators ensure both the LED current matching and the brightness uniformity. The LED current can be programmed by an external resistor, R SET, connected between the RSET pin and ground. LED current of up to 30mA are supported by the input supply voltage over a range of 2.7V to 5.5V, making the device optimized for Li-Ion battery applications. The PAM2701 has a fixed switching frequency of 1MHz, allowing the use of very small value ceramic capacitors. The enable input pin allows the device to be set in shutdown mode, and the current consumption is reduced to less than 1μA. LED dimming can be done by several methods including using a DC voltage to set the RSET pin current, adding a switched resistor in parallel with R SET, or applying a PWM signal to CTRx pin or EN pin. Peak Efficiency: 90% Individual Current Regulation 3-bit Digital Output Control Two modes of operation:1x and 1.5x Current Matching with a Max Tolerance of 3% Output Current up to 30mA per LED Total LED Current up to 4*30mA=120mA Fixed Frequency of 1MHz Open LED Protection Space Saving Package QFN 3mmx3mm and QFN 4mmx4mm Pb-Free Package Applications n n n n n n n n Cellular Phones LED Backlighting LCD Modules Handheld Devices Digital Cameras PDAs PMPs MP3 Players Typical Application 1μF 1μF 8 7 EN C IN 1μF Control 0 Control 1 Control 2 R SET 24kΩ C1 + VIN 9 11 10 C2 - C1 - C2 + 6 Co 1μF VOUT 1 EN PAM2701 V IN 2 3 4 5 CTR0 CTR1 CTR2 RSET GND LED1 LED2 LED3 LED4 16 15 14 13 20mA 12 Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 1 PAM2701 4-Channel Regulated Charge Pump White LED Driver B lock Diagram C1 1μF 1μF C1 + C2 C2 + VIN C IN 1μF 1x Mode ( LDO ) 1 . 5x Charge Pump VOUT CO 1μF 1MHz Oscillator Mode Control LED1 LED2 EN 1 . 2V Ref RSET R SET 24KΩ LED3 LED4 20mA Current Setting CTR0 CTR1 CTR2 LED Output 4 Current Sink Regulators Select Table 1:LED Enable Logic Control Lines CTR2 0 0 0 0 1 1 1 1 CTR1 0 0 1 1 0 0 1 1 CTR0 0 1 0 1 0 1 0 1 LED4 ON ON LED Outputs LED3 ON ON ON LED2 ON ON ON ON LED1 ON ON ON ON - Note:1=logic high(or V IN) 0=logic low(or GND) - =LED output off Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 2 PAM2701 4-Channel Regulated Charge Pump White LED Driver Pin Configuration & Marking Information QFN 3mmx3mm/4mmx4mm 16 15 1 2 3 4 5 Pin Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 14 13 12 P2701 XAT YW 11 10 9 X: Internal Code A: Assembly Code T: Testing Code Y: Year W: Week 6 7 8 Function Enable Input, Active High Digital Control Input 0 Digital Control Input 1 Digital Control Input 2 Set Resistance Charge pump output connected to the LED anodes Supply Voltage Bucket Capacitor 1 Terminal Bucket Capacitor 1 Terminal Bucket Capacitor 2 Terminal Bucket Capacitor 2 Terminal Ground Reference LED4 Cathode Terminal LED3 Cathode Terminal LED2 Cathode Terminal LED1 Cathode Terminal Name EN CTR0 CTR1 CTR2 RSET VOUT VIN C1+ C1C2C2+ GND LED4 LED3 LED2 LED1 Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 3 PAM2701 4-Channel Regulated Charge Pump White LED Driver Absolute Maximum Ratings These are stress ratings only and functional operation is not implied . Exposure to absolute maximum ratings for prolonged time periods may affect device reliability . All voltages are with respect to ground . VIN , VOUT , LEDx Pin Voltage.........- 0.3V to 6.6V EN , CTRx Pin Voltage.......................- 0.3V to V IN RSET Pin Voltage............................. .-0.3V to V IN Ambient Temperature Range........- 40 °C to 85 °C Storage Temperature Range.........-65°C to 150°C Lead Temperature......................................300 °C ESD Ratings Human Body Model ( HBM).........................2000V Recommended Operating Conditions V IN...................................................2.7V to 5.5V Max. Supply Voltage (for Max. duration of 30 minutes)................................................6.4V Input/Output/Bucket Capacitors....1±20%μF(TYP.) Ambient Temperature.....................-40 °C to 85 °C I LED per LED...................................0mA to 30mA Thermal Information Parameter Thermal Resistance (Junction to Ambient) Power Dissipation， PD @TA =25℃ Symbol θJA PD Package QFN 3*3mm QFN 4*4mm QFN 3*3mm QFN 4*4mm Maximum 34 25 2.9 4.0 Unit °C/W W Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 4 PAM2701 4-Channel Regulated Charge Pump White LED Driver E lectrical Characteristic Parameter Input Voltage Range Shutdown Current Quiescent Current RSET Regulated Voltage Programmed LED Current LED Current Accuracy LED Channel Matching Output Resistance (Open Loop) Charge Pump Frequency V IN at Mode Transition from 1x to 1.5x 1x to 1.5x Mode Transition Dropout Delay Input Leakage Current High Detect Threshold Low Detect Threshold T DROP IEN-CTR V EN-CTRH V EN-CTRL On Inputs EN,CTR0,1&2 On Inputs EN,CTR0,1&2 On Inputs EN,CTR0,1&2 1.5 0.4 T A= 25 °C , V IN= 3.5V, C IN=C O=1μF, unless otherwise noted . Symbol V IN ISD IQ VRSET RSET =90kΩ ILED ILED-A CC ILED-DEV RO fOSC V IN-Tran ILED =15mA ILED =20mA (ILED-ILEDAVG)/ILEDAVG 1x Mode, IO=100mA 1.5x Mode, IO=100mA RSET =29.3kΩ RSET =14.7kΩ VEN =0V Shutdown Mode 1x Mode, No Load 1.5x Mode, No Load 1.19 Conditions Min 2.7 0.05 0.6 2.5 1.23 5.0 15.0 30.0 ±5 ±3 1.7 4.3 1.0 3.45 3.60 10 1 Typ Max 5.5 1 1.2 5 1.25 Unit V μA mA mA V mA mA mA % % Ω Ω MHz V V μs μA V V Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 5 PAM2701 4-Channel Regulated Charge Pump White LED Driver Typical Characteristics V IN = 3.6V, EN = V IN, R SET = 24kΩ, C IN=C O=1μF,T A = 25°C, unless otherwise noted. 2. Efficiency vs Output Current (4 LEDs) 1. Efficiency vs Input Voltage (4 LEDs) 100 90 100 90 Efficiency (%) 80 70 60 50 40 2.4 3 3.6 4.2 4.8 5.4 Input Voltage (V) 15mA per LED 20mA per LED Efficiency (%) 80 70 60 50 40 10 40 70 100 130 160 Output Current (mA) V IN=3.2V V IN=4.2V 24 22 20 18 16 14 12 10 3. LED Current vs Input Voltage (4 LEDs) 4. Supply Current vs Input Voltage (4 LEDs) 140 120 Supply Current (mA) LED Current (mA) 20mA per LED 100 80 60 40 20 0 20mA per LED 15mA per LED 15mA per LED 2.8 3.1 3.4 3.7 4 4.3 2.4 3 3.6 4.2 4.8 5.4 Input Voltage (V) Input Voltage (V) 3.00 5. Ground Current vs Input Voltage Oscillator Frequency (MHz) 1.1 6. Oscillator Frequency vs Input Voltage Ground Current (mA) 2.50 2.00 1.5X Mode 1.50 1.00 0.50 0.00 2.8 3.1 3.4 3.7 4 4.3 Input Voltage (V) 1X Mode 1.05 1 0.95 0.9 2.8 3.2 3.6 Input Voltage (V) 4 4.4 Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 6 PAM2701 4-Channel Regulated Charge Pump White LED Driver Typical Characteristics 7 6 7. Output Voltage vs Input Voltage 1.5X Mode 4.5 4 8. Output Resistance vs Input Voltage 5 4 3 2 1 0 2.8 3.1 3.4 3.7 4 4.3 Input Voltage (V) 1X Mode Output Resitance (Ω) Output Voltage (V) 3.5 3 2.5 2 1.5 1 2.8 3.1 3.4 3.7 4 4.3 Input Voltage (V) 1.5X Mode，IO=100mA 1X Mode，IO=100mA 9. LED Current Setting Using the External Resistor R SET LED Current vs R SET Resistance 35 30 25 20 15 10 5 0 0 100 200 300 400 500 600 R SET RSET Resistance (KΩ) 10.LED Current Setting Using a DC Voltage to RSET Pin LED Current vs Analog Control Voltage 35 30 LED Current (mA) LED Current (mA) 25 20 15 10 5 0 0 0.3 0.6 0.9 1.2 Analog Control Voltage (V) 11.LED Current Setting Using a PWM Signal to EN Pin 35 30 LED Current vs Duty Cycle @ f=100Hz 35 30 LED Current vs Duty Cycle @ f=1KHz LED Current (mA) LED Current (mA) 25 20 15 10 5 0 0 V IN=3.2V 25 20 15 10 5 0 V IN=3.2V V IN=4.2V V IN=4.2V 20 40 60 80 100 0 20 40 60 80 100 PWM Duty Cycle (%) PWM Duty Cycle (%) Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 7 PAM2701 4-Channel Regulated Charge Pump White LED Driver Typical Characteristics 12.LED Current Setting Using a PWM Signal to CTR0 Pin LED Current vs Duty Cycle @ f=100HZ LED Current vs Duty Cycle @ f=1KHZ V IN=3.2V 35 30 LED Current (mA) 35 30 LED Current (mA) V IN=3.2V 25 20 15 10 5 0 0 20 40 60 80 100 PWM Duty Cycle (%) V IN=4.2V 25 20 15 10 5 0 0 20 40 60 80 100 PWM Duty Cycle (%) V IN=4.2V 13.Output Ripple 1X Mode 1.5X Mode Vin AC Coupling Iin AC Coupling Vo AC Coupling Vin AC Coupling Iin AC Coupling Vo AC Coupling Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 8 PAM2701 4-Channel Regulated Charge Pump White LED Driver Application Information Detailed Description As shown in the block diagram on page 2, the main components within the PAM2701 include a fractional charge pump, mode selection circuit, output selection logic, LED current setting detection circuit, and 4 current sense circuits. The fractional charge pump multiplies the input voltage a multiple of 1X and 1.5X times the input voltage. The charge pump switches at a fixed 1MHz when the mode is 1.5X. The charge pump does not switch during 1X mode, saving power and improving efficiency. The mode selection circuit automatically selects the mode as 1X or 1.5X based on circuit conditions such as LED voltage, input voltage and load current. 1X is the more efficient mode than 1.5X mode. Table 1 on page 2 shows the output selection logic control over the LED outputs for on and off functions with 8 different output states. The current set and detection circuit uses an external resistor and a 1.20V reference to program the LED current. 4 current regulating circuits sink matched currents from the LEDs. LEDs with matched forward voltage will produce the best possible matched currents. For best matching performance it is recommended that the Vf between LEDs be under 250mV. The unused LED channels can be turned off by CTR0, CTR1 and CTR2, and connecting the respective LED pins to VOUT pin, in which case, the corresponding LED driver sink current is only about 20 μ A. The most basic means of setting the LED current is connecting a resistor from R SET to GND, as shown in the application circuit on Page 1. The resistor R SET establishes the reference current needed for a constant LED current. Values of R SET for a fixed LED current are given in Table 2, “Typical R SET Resistance vs. LED Current”. Table 2: R SET Resistance Selection ILED(mA) 30 20 15 10 9 8 7 6 5 4 3 2 1 RSET(kΩ) 14.7 21.8 29.3 44.1 49.4 55.7 64.2 75.0 90.0 114.2 156.5 238.0 540.0 Standard Value (kΩ) 14.7 22.0 29.4 44.2 49.9 56.0 63.4 75.0 88.7 115.0 158.0 237.0 536.0 Value % Difference 0..0% 0.9% 0.3% 0.2% 1.0% 0.5% 0.3% 0.0% -0.3% 0.7% 0.9% -0.4% -0.7% Method 2: LED Current Setting with a DC Voltage to RSET Pin Method 2 is for setting the LED current to control brightness. An example circuit is shown in Figure 1, employing a 14.7k resistor and an analog input DC voltage, V SET, which varies from 1.2V to 0V to control LED current from 1mA to 30mA. Table 3 shows the resulting output. If necessary, the analog V SET voltage can be sourced from a voltage higher than 1.20V, but the source must be divided down so that the V SET mode will not exceed 1.20V. For lower current and higher resolution applications , a larger resistor may be used instead. PWM applications are also possible with this circuit by application of RC filtering (Consult with PAM for detail application support). Methods for Setting LED Current There are 4 methods for setting and adjusting the LED current outlined here. The methods are: 1) R SET only 2) Analog Reference V SET 3) PWM Input at CTR0 4) PWM Input at EN Method 1: LED Current Setting with an External Resistor R SET Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 9 PAM2701 4-Channel Regulated Charge Pump White LED Driver Application Information Table 3: Analog Voltage for LED Current Control VSET(V) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 ILED(mA) 30.0 27.7 25.3 22.9 20.5 18.1 15.7 VIN Figure 2: PWM Signal at CTR0 pin for LED Current Control Co 1.0 μ F VSET(V) 0.7 0.8 0.9 1.0 1.1 1.2 ILED(mA) 13.3 10.9 8.4 6.0 3.6 1.1 100Hz to 1kHz D1 D2 D3 D4 LED1 LED2 LED3 LED4 EN PWM GND C2+ CTR0 PAM2701 CTR1 C2C1C1+ C1 1.0 μ F Cin 1.0 μ F C2 1.0 μ F CTR2 RSET VOUT VIN R SET 14.7kΩ Figure 1: Analog Voltage for LED Current Control Method 4: LED Current Setting with a PWM Signal to EN Pin Co 1.0μF LED1 EN CTR0 D1 D2 D3 D4 LED2 LED3 LED4 GND C2+ PAM2701 CTR1 C2- C2 1.0μF CTR2 RSET VOUT VIN C1+ RSET 14.7 kΩ VSET VIN Cin 1.0μF 1.0μF Method 3: LED Current Setting with a PWM Signal to CTRx Pin In circuit in Figure 2 four LEDs are turned on and off by a PWM signal on the CTR0. A resistor R SET is used to set the on state current and the average LED current is then proportional to the percentage of on-time when the CTR0 pin is logic low. Average LED current is approximately equal to: I AVG = (t ON*I LED_ON)/ (t ON + t OFF) It is recommended that PWM frequency is between 100Hz and 1kHz. Due to start up delay and ramp up time, frequency >1kHz will result in error in the average value of I LED. Frequency 1kHz will result in error in the average value of I LED. Frequency