PAM2701 4-Channel Regulated Charge Pump White LED Driver Features n n n n n n n n n n n Description 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 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. Applications n n n n n n n n 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. Cellular Phones LED Backlighting LCD Modules Handheld Devices Digital Cameras PDAs PMPs MP3 Players 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. Typical Application 1μF 8 7 V IN EN C IN 1μF Control 0 Control 1 Control 2 C1 + 1μF 9 10 11 C1 - C2 + VIN C2 - 6 VOUT 1 EN PAM2701 2 3 4 5 CTR0 LED1 CTR1 LED2 CTR2 LED3 RSET R SET 24kΩ LED4 16 15 14 Co 1μF 20mA 13 GND 12 Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 1 PAM2701 4-Channel Regulated Charge Pump White LED Driver Block Diagram C1 - VIN 1μF 1μF C1 + C2 C2 + 1x Mode ( LDO ) 1 . 5x Charge Pump C IN 1μF VOUT CO 1μF Mode Control 1MHz Oscillator LED1 EN LED2 LED3 1 . 2V Ref LED4 RSET R SET 24KΩ Current Setting CTR0 CTR1 20mA LED Output 4 Current Sink Regulators Select CTR2 Table 1:LED Enable Logic Control Lines LED Outputs CTR2 CTR1 CTR0 LED4 LED3 LED2 LED1 0 0 0 - - - ON 0 0 1 - - ON - 0 1 0 - ON - - 0 1 1 ON - - - 1 0 0 - - ON ON 1 0 1 - ON ON ON 1 1 0 ON ON ON ON 1 1 1 - - - - 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 14 13 1 X: Internal Code A: Assembly Code T: Testing Code Y: Year W: Week 12 2 11 P2701 XAT YW 3 10 4 9 5 6 7 8 Pin Number Name Function 1 EN 2 CTR0 Digital Control Input 0 3 CTR1 Digital Control Input 1 4 CTR2 Digital Control Input 2 5 RSET Set Resistance 6 VOUT Charge pump output connected to the LED anodes 7 VIN Supply Voltage 8 C1+ Bucket Capacitor 1 Terminal 9 C1- Bucket Capacitor 1 Terminal 10 C2- Bucket Capacitor 2 Terminal 11 C2+ Bucket Capacitor 2 Terminal 12 GND Ground Reference 13 LED4 LED4 Cathode Terminal 14 LED3 LED3 Cathode Terminal 15 LED2 LED2 Cathode Terminal 16 LED1 LED1 Cathode Terminal Enable Input, Active High 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 Input/Output/Bucket Capacitors....1±20%μF(TYP.) Ambient Temperature.....................-40 °C to 85 °C I LED per LED...................................0mA to 30mA V IN...................................................2.7V to 5.5V Max. Supply Voltage (for Max. duration of 30 minutes)................................................6.4V Thermal Information Parameter Thermal Resistance (Junction to Ambient) Power Dissipation，PD @TA =25℃ Symbol θJA PD Package Maximum QFN 3*3mm 34 QFN 4*4mm 25 QFN 3*3mm 2.9 QFN 4*4mm 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 Electrical Characteristic T A= 25 °C , V IN= 3.5V, C IN=C O=1μF, unless otherwise noted. Parameter Symbol Input Voltage Range V IN Shutdown Current ISD Quiescent Current IQ RSET Regulated Voltage VRSET Programmed LED Current ILED LED Current Accuracy ILED-A CC LED Channel Matching ILED-DEV Output Resistance (Open Loop) RO Charge Pump Frequency fOSC V IN at Mode Transition from 1x V IN-Tran to 1.5x 1x to 1.5x Mode Transition Dropout Delay Conditions Min Typ 2.7 Max Unit 5.5 V VEN =0V Shutdown Mode 0.05 1 μA 1x Mode, No Load 0.6 1.2 mA 1.5x Mode, No Load 2.5 5 mA 1.19 1.23 1.25 V RSET =90kΩ 5.0 mA RSET =29.3kΩ 15.0 mA RSET =14.7kΩ 30.0 mA ±5 % (ILED-ILEDAVG)/ILEDAVG ±3 % 1x Mode, IO=100mA 1.7 Ω 1.5x Mode, IO=100mA 4.3 Ω 1.0 MHz ILED =15mA 3.45 V ILED =20mA 3.60 V 10 μs T DROP Input Leakage Current IEN-CTR On Inputs EN,CTR0,1&2 High Detect Threshold V EN-CTRH On Inputs EN,CTR0,1&2 Low Detect Threshold V EN-CTRL On Inputs EN,CTR0,1&2 1 1.5 μA V 0.4 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 100 100 90 90 Efficiency (%) Efficiency (%) 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) 80 70 60 20mA per LED 50 80 V IN=4.2V 70 60 V IN=3.2V 50 15mA per LED 40 40 2.4 3 3.6 4.2 4.8 5.4 10 40 70 Input Voltage (V) 24 140 120 20 Supply Current (mA) LED Current (mA) 160 4. Supply Current vs Input Voltage (4 LEDs) 3. LED Current vs Input Voltage (4 LEDs) 20mA per LED 18 16 14 15mA per LED 12 20mA per LED 100 80 60 40 15mA per LED 20 10 0 2.8 3.1 3.4 3.7 4 4.3 2.4 3 3.6 Input Voltage (V) 5. Ground Current vs Input Voltage 1.1 2.50 2.00 1.5X Mode 1.50 1X Mode 1.00 4.2 4.8 5.4 Input Voltage (V) Oscillator Frequency (MHz) Ground Current (mA) 130 Output Current (mA) 22 3.00 100 0.50 0.00 6. Oscillator Frequency vs Input Voltage 1.05 1 0.95 0.9 2.8 3.1 3.4 3.7 4 4.3 2.8 Input Voltage (V) 3.2 3.6 4 4.4 Input Voltage (V) 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. Output Voltage vs Input Voltage 7 4 1.5X Mode Output Resitance (Ω) Output Voltage (V) 6 5 4 3 2 8. Output Resistance vs Input Voltage 4.5 1X Mode 1 3.5 1.5X Mode，IO=100mA 3 2.5 1X Mode，IO=100mA 2 1.5 0 1 2.8 3.1 3.4 3.7 4 4.3 2.8 3.1 3.4 Input Voltage (V) 4 4.3 Input Voltage (V) 9. LED Current Setting Using the External Resistor R SET 10.LED Current Setting Using a DC Voltage to RSET Pin LED Current vs R SET Resistance LED Current vs Analog Control Voltage 35 35 30 30 LED Current (mA) LED Current (mA) 3.7 25 20 15 10 25 20 15 10 5 5 0 0 0 100 200 300 400 500 0 600 0.3 0.6 0.9 1.2 Analog Control Voltage (V) R SET Resistance (KΩ) RSET 11.LED Current Setting Using a PWM Signal to EN Pin LED Current vs Duty Cycle @ f=100Hz 35 30 30 25 LED Current (mA) LED Current (mA) LED Current vs Duty Cycle @ f=1KHz 35 V IN=3.2V 20 15 10 V IN=4.2V V IN=3.2V 25 20 15 10 V IN=4.2V 5 5 0 0 0 20 40 60 80 0 100 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 35 12.LED Current Setting Using a PWM Signal to CTR0 Pin LED Current vs Duty Cycle @ f=100HZ V IN=3.2V 30 30 V IN=3.2V LED Current (mA) LED Current (mA) LED Current vs Duty Cycle @ f=1KHZ 35 25 20 15 V IN=4.2V 10 25 20 15 5 5 0 0 0 20 40 60 80 V IN=4.2V 10 0 100 20 40 60 80 100 PWM Duty Cycle (%) PWM Duty Cycle (%) 13.Output Ripple 1.5X Mode 1X Mode Vin AC Coupling Vin AC Coupling Iin AC Coupling Iin AC Coupling Vo 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 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. 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 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”. 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. Table 2: R SET Resistance Selection Standard Value % Value (kΩ) Difference 14.7 14.7 0..0% 20 21.8 22.0 0.9% 15 29.3 29.4 0.3% 10 44.1 44.2 0.2% 9 49.4 49.9 1.0% 8 55.7 56.0 0.5% 7 64.2 63.4 0.3% The current set and detection circuit uses an external resistor and a 1.20V reference to program the LED current. 6 75.0 75.0 0.0% 5 90.0 88.7 -0.3% 4 114.2 115.0 0.7% 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. 3 156.5 158.0 0.9% 2 238.0 237.0 -0.4% 1 540.0 536.0 -0.7% 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. ILED(mA) RSET(kΩ) 30 Method 2: LED Current Setting with a DC Voltage to RSET Pin 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. 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 Figure 2: PWM Signal at CTR0 pin for LED Current Control Table 3: Analog Voltage for LED Current Control VSET(V) ILED(mA) VSET(V) ILED(mA) 0.0 30.0 0.7 13.3 0.1 27.7 0.8 10.9 0.2 25.3 0.9 8.4 Co 1.0 μ F D1 D2 D3 D4 LED1 LED2 LED3 LED4 100Hz to 1kHz CTR0 PWM 22.9 1.0 6.0 CTR1 0.4 20.5 1.1 3.6 CTR2 18.1 0.6 15.7 1.2 C2+ PAM2701 0.3 0.5 GND EN C1- RSET VOUT VIN 1.1 C2 1.0 μ F C2- C1+ R SET C1 1.0 μ F Cin 1.0 μ F 14.7kΩ VIN Figure 1: Analog Voltage for LED Current Control Method 4: LED Current Setting with a PWM Signal to EN Pin D1 Co 1.0μF LED1 D2 LED2 D3 LED3 D4 The four LEDs are turned on and off by applying a PWM signal to the EN pin in circuit in Figure 3. The circuit is the same as one in method 3, using a resistor R SET to set the on state current and the average LED current proportional to the percentage of on-time when the EN pin is logic low. Average LED current is approximately equal to: I AVG = (t ON*I LED_ON)/ (t ON + t OFF) Similarly, 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 <100Hz can cause the LEDs to blink visibly LED4 GND EN C2+ CTR0 PAM2701 C2- CTR1 C2 1.0μF CTR2 RSET VOUT VIN C1+ RSET 14.7kΩ VSET 1.0μF Cin 1.0μF VIN Method 3: LED Current Setting with a PWM Signal to CTRx Pin Figure 3: PWM Signal at EN pin for LED Current Control 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 <100Hz can cause the LEDs to blink visibly. Co 1.0 μ F 100Hz to 1kHz D1 LED1 D2 D3 LED2 LED3 LED4 GND EN PWM D4 CTR0 C2+ PAM2701 C1- CTR2 RSET VOUT VIN C2 1.0 μ F C2- CTR1 C1+ C1 R SET 14.7kΩ 1.0 μ F Cin 1.0 μ F VIN Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 10 PAM2701 4-Channel Regulated Charge Pump White LED Driver Application Information PCB Layout Figure 4: PCB layout When the driver is in the 1.5X charge pump mode, the 1MHz switching frequency operation requires to minimize the trace length and impedance to ground on all 4 capacitors. A ground plane should cover the area on the bottom side of the PCB opposite to the IC and the bypass capacitors. Capacitors C IN and Co should be short connected to ground with multiple vias as shown on Figure4. Square copper area matches the QFN 16 exposed pad (GND) which is connected by a trace to the pin 12 pad (GND). A large via (metalized hole) centered in the square pad provides a low impedance connection to the ground plane on the opposite side of the PCB and allows the heat dissipation of the LED driver to achieve excellent thermal performance. Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 11 PAM2701 4-Channel Regulated Charge Pump White LED Driver Ordering Information PAM2701 X X X Shipping Package Pin Number Package Type Package Type Pin Number Shipping Package J: QFN 3mmx3mm E: 16 R: Tape & Reel K: QFN 4mmx4mm Part Number Package Type MOQ PAM2701JER Thin QFN-16 3mm×3mm 3,000 Units/Tape & Reel PAM2701KER Thin QFN-16 4mm×4mm 3,000 Units/Tape & Reel Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 12 PAM2701 4-Channel Regulated Charge Pump White LED Driver Outline Dimension 3x3 mm TQFN 16 DIMENSIONS (Millieters) MIN TYP MAX A 0.70 0.75 0.80 A1 0.00 0.02 0.05 A2 0.20 b 0.18 0.25 0.30 D 2.90 3.00 3.10 D1 1.55 1.70 1.80 E 2.90 3.00 3.10 E1 1.55 1.70 1.80 e L 0.50BSC 0.30 0.40 N 16 aaa 0.08 bbb 0.10 0.50 Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 13 PAM2701 4-Channel Regulated Charge Pump White LED Driver Outline Dimension 4x4mm QFN 16 DIMENSIONS (Millieters) MIN TYP MAX A 0.80 0.90 1.00 A1 0.00 0.02 0.05 A2 0.20 b 0.25 0.30 0.35 D 3.90 4.00 4.10 D1 2.00 2.15 2.25 E 3.90 4.00 4.10 E1 2.00 2.15 2.25 e L 0.65BSC 0.45 0.55 N 16 aaa 0.08 bbb 0.10 0.65 Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 14