PAM2810 4-Channel Programmable LED Current Sink Features n n n n n n n n n n Description The PAM2810 provides 4 regulated current sinks, capable of sinking up to 40mA current to accommodate 4 white LEDs. It requires no charge pump, has no noise and EMI, and significantly improves the efficiency in Li bettery range. Cost Effective LED Driver Support up to 4 White LEDs Output Current up to 40mA per LED Low Dropout Voltage Ultra Low Quiescent Supply Current: 65 μ A (typ) No Noise and EMI Shutdown Current Less than 1 μ A Over Temperature Protection Small Packages : SOT23-8 and DFN 2mmx2mm Pb-free Package LED brightness can be controlled by PWM techniques. The constant current sink is set with an external sense resistor. Alternatively, a PWM signal applied to the EN pin can vary the anticipated brightness of the LED. The device is in shut down mode when the EN input is logic low. Applications n White LED for LCD Display Backlights n White LED Keypad Backlights n 1-Cell Li-Ion Battery-operated Equipment Including PDAs, Hand-held PCs, Cellular Phone The PAM2810 is available in SOT23-8 and DFN 2 mmX2mm Packages. Typical Application Circuit VIN C1 0.1μF 4 VIN 2 1 EN LED1 8 LED2 7 PAM2810 LED3 6 ISET LED4 5 GND R1 6.2k 3 Power Analog Microelectronics , Inc www.poweranalog.com 08/2008 Rev 1.1 1 PAM2810 4-Channel Programmable LED Current Sink Typical Application Circuit V BAT VIN VIN C1 0.1μF C1 0.1μF 4 VIN 4 VIN 2 LED1 EN PAM2810 1 LED2 LED3 ISET LED4 8 2 7 LED1 EN PAM2810 6 1 5 LED3 ISET LED4 7 6 5 NC GND GND R1 6.2kΩ LED2 8 R1 6.2k Ω 3 3 Block Diagram VIN VIN LED1 C IN 0.1 μ F LED2 1.22V Ref LED3 LED4 EN ISET Current Setting Current Sinks RSET GND Power Analog Microelectronics , Inc www.poweranalog.com 08/2008 Rev 1.1 2 PAM2810 4-Channel Programmable LED Current Sink Pin Configuration Top View SOT23-8 Top View DFN 2mmX2mm VIN 1 EN 3 ISET 4 Pin Number LED1 7 LED2 6 LED3 5 LED4 ISET 1 EN 2 GND 3 VIN 4 EJXYW 2 EJX YW GND 8 Name Description 4 VIN Input Voltage 2 3 GND Ground 3 2 EN 4 1 ISET LED Current Adjustment Pin 5 5 LED4 LED4 Cathode Terminal 6 6 LED3 LED3 Cathode Terminal 7 7 LED2 LED2 Cathode Terminal 8 8 LED1 LED1 Cathode Terminal DFN2x2 SOT23-8 1 8 LED1 7 LED2 6 LED3 5 LED4 EJ: Product Code X: Internal Code Y: Year W: Week Enable, Allow PWM Brightness Control, Active High Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.1 3 PAM2810 4-Channel Programmable LED Current Sink 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 . Input Voltage Range............................-0.3V to 6V Operation Junction Temperature.....-40°C to 125 °C PWM Pin voltage............... -0.3V to (VIN+0.3V)/6V Storage Temperature.....................-65 °C to 150 °C Maximum Junction Temperature..................150°C Soldering Temperature....................... 300°C,5sec Recommended Operating Conditions Input Voltage Range.......................... 2.7V to 5.5V Operation Temperature Range.........-40 °C to 85 °C Thermal Information Parameter Symbol Thermal Resistance Package Maximum SOT23-8 250 DFN 102 SOT23-8 130 DFN 20 Unit θJA (Junction to Ambient) ºC/W Thermal Resistance θJC (Junction to Case) Electrical Characteristic T A=25°C, V IN=3.6V, R SET=5.1k Ω, V LEDX=0.5V, unless otherwise noted. PARAMETER Input Voltage Output Current Current Matching Between Any Two Outputs Current Sink Dropout ISET PIN Voltage Output Current to Current Set Ratio Symbol CONDITIONS Vf+V LED V IN ILEDX MIN （Note） TYP MAX UNITS 3.6 5.5 V 40 mA ±5 % 0.25 V VDD=5V ILED-MATCH VDROPOUT Rset=3kΩ,ILEDX=40mA V SET 1.22 ILEDX/ISET 100 Quiescent Supply Current IQ Shutdown Supply Current ISHDN EN Input Logic High VHI EN Input Logic Low V LO EN Pin Current IEN V Rset=10MΩ,with no loads 65 80 μA EN=logic low 0.1 1 μA 1.4 V 0.4 V V(EN) = 1.5V 0.1 1 μA V(EN) = 0V 0.1 1 μA Note: Vf: LED forward voltage; V LED: voltage of LEDx pins. Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.1 4 PAM2810 4-Channel Programmable LED Current Sink Typical Performance Characteristics T A=25°C, V IN=3.6V, R SET=5.1k Ω, V LEDX=0.5V, unless otherwise noted. LED Curent VS Input Voltage 45 45 40 40 35 35 LED Curent(mA) LED Current (mA) LED Current VS LED Pin Voltage 30 25 20 15 10 30 25 20 15 10 5 R=12.7KΩ R=6.2KΩ R=4.3KΩ R=3.2KΩ 5 0 0.3 0.6 0.9 1.2 1.5 3 3.5 R=3.2KΩ 4 4.5 5 5.5 Input Voltage(V) LED Pin Voltage(V) VIset VS Input Voltage LED Current VS Rset 50 1.2125 45 40 LED Current(mA) 1.2135 1.2115 Viset(V) R=6.2KΩ R=4.3KΩ 0 0 1.2105 1.2095 35 30 25 20 15 10 5 1.2085 1.2075 0 3 3.5 4 4.5 5 5.5 0 5 10 Input Voltage(V) 20 LED Current vs PWM Duty Cycle 30 90 80 25 LED Current (mA) 100 70 60 50 40 30 20 20 15 10 5 Rset=6.2k 10 0 15 Rset(kΩ) Efficiency VS Input Voltage Efficiency(%) R=12.7KΩ 0 3 3.25 3.5 3.75 4 4.25 4.5 0 Input Voltage(V) 20 40 60 80 100 PWM Duty Cycle (%) Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.1 5 PAM2810 4-Channel Programmable LED Current Sink Application Information The PAM2810 is a 4-channel programmable white-LED driver. The matched current regulators each have a 100:1 ratio between the LEDx outputs and the ISET current. The PAM2810 is capable of supplying 40mA per channel with the proper selection of the external RSET resistor, with a total of 160mA output current available. LED brightness control of PAM2810 can be achieved with a PWM signal. Table 2. PWM Frequency and Duty cycle Frequency Cycle 100Hz 10ms > 0.5 100 1kHz 1ms > 5 100 Output Current Capability 2 kHz 500μs > 10 100 The PAM2810 is capable of providing up to 40mA per LED under an input voltage of 2.7V to 5.5V. An external resistor is used to set the output current, as approximated with the following equation: 4 kHz 250μs > 20 100 8 kHz 125μs > 40 100 R SET=100 *(1.22V / I LEDX ) 10 kHz 100μs > 50 100 In order that the output currents could be regulated properly, the LEDx pin voltage(V LEDX) must be larger than the dropout voltage of the current sink(V DROPOUT). To ensure the desired current is obtained, apply the following equation to determine the minimum input voltage: The maximum PWM frequency can be selected according to the table above. If the PWM frequency is much less than 100Hz, flickering may be seen in the LEDs. For the PAM2810, zero duty cycle will turn off the LEDs and a 50% duty cycle will result in an average ILED being half of the programmed LED current. For example, if RSET is set to program 20mA, a 50% duty cycle will result in an average ILED of 10mA. RSET should be chosen not to exceed the maximum current capability of the device. V IN - V DIODE = V LEDX ≥ V DROPOUT V DIODE is the diode forward voltage, and some typical value of V DROPOUT can be found from the following table. Table 1. I LED, R SET and V DROPOUT ILED RSET VDR OPOUT 10mA 12.7kΩ 40mV 20mA 6.2kΩ 80mV 30mA 4.3kΩ 120mV 40mA 3.2kΩ 150mV Duty-Cycle Request Shutdown When the EN pin is logic low, the PAM2810 will be in shutdown mode. While disabled, the PAM2810 typically draws 0.1 μ A current form the power supply. There is no internal pull-up or pull-down on the EN pin. Over Temperature Protection PWM Brightness Control T h e PA M 2 8 1 0 e q u i p s o v e r t e m p e r a t u r e protection. When the junction temperature (T J) exceeds +150°C, the current source turns off automatically. The device will turn on again after the IC’s T J cools down under +125°C. Operating at absolute maximum temperature is not recommended. Brightness control can be realized by applying a PWM signal to the EN pin. The constant current is set by the external resistor selected using the RSET equation. The LED brightness is proportional to the duty cycle (D) of the PWM signal. The PWM frequency (f) should be limited to accommodate the start-up time (50 μ s) of the device. D * (1/f) > 50 μ s Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.1 6 PAM2810 4-Channel Programmable LED Current Sink Parallel LEDx Outputs for Increased Current Drive Connecting outputs in parallel does not affect internal operation of the PAM2810 and has no impact on the electrical characteristics. Output pins LED1 to LED4 may be connected together in any combination to sink higher current through fewer LEDs. For example in Figure 1, outputs LED1 and LED2 are connected together to drive one LED while LED3 and LED4 are connected together to drive a second LED. If less than four LEDs connected, the left pin can be floating or connected to GND, as shown in Typical Application Circuit on page 2.Connecting to GND is recommended. The current calculating method is the same as the RSET equation mentioned. Power Dissipation VIN Cin The maximum allowable power dissipation that the package is capable of handling can be determined as follows: LED1 LED2 0. 1μF LED3 EN GND P DMAX = (T JMAX - T A) / θ JA LED4 Where T JMAX is the maximum junction temperature, T A is the ambient temperature, and θ JA is the junction-to-ambient thermal resistance of the specified package. The DFN 2x2 package has a θ JA of 80°C/W and the SOT23-8 250°C/W. This value of θ JA is highly dependant upon the layout of the PCB. The actual power dissipated by the PAM2810 follows the equation: ISET Rset Figure 1. Two Parallel Connected LEDs With this configuration, two parallel current sinks of equal value both provide current to each LED. If the current sink provides 10mA each, every LED can be drived with 20mA and gets double brightness. Other combinations of parallel outputs can be implemented similarly, such as in Figure 2. P DISS=(V IN *I IN) - N(V DIODE * I LEDX) Where N equals the number of active outputs, V DIODE is the LED forward voltage, and I LEDX is the current supplied to the LEDx. Input Capacitor Selection VIN Cin The PAM2810 is designed to work under a stable input voltage. To ensure the stability of input, it may be necessary to add a small input capacitor to help filter out any noise that probably appears on the line. Surface-mount multi-layer ceramic capacitors are recommended, which are small and inexpensive. A capacitance of 0.1 μ F is typically sufficient. LED1 LED2 0.1μF LED3 EN GND LED4 ISET Rset Figure 2. One Parallel Connected LED Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.1 7 PAM2810 4-Channel Programmable LED Current Sink Ordering Information PAM2810 X X Package Type Pin Configuration Pin Configuration Package Type A: SOT23-8 B: A: 1: VIN 1: ISET 2: GND 2: EN 3: EN 3: GND 4: ISET 4: VIN 5: LED4 5: LED4 6: LED3 6: LED3 7: LED2 7: LED2 8: LED1 8: LED1 G: DFN 2x2-8 Part Number Marking Package Shipping PAM2810AG EJXYW DFN 2x2-8 3,000 units/Tape & Reel PAM2810BA EJXYW SOT23-8 3,000 units/Tape & Reel Please consult PAM sales office or authorized distributors for more details. Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.1 8 PAM2810 4-Channel Programmable LED Current Sink Outline Dimensions SOT23-8 (REF.) 0.20 (MAX) (TYP) (REF.) Symbol A A1 A2 c D E E1 Dimensions In Millimet ers Min Max 1.45 MAX 0 0.10 1.10 1.30 0.12 (REF) 3.10 2.70 3.00 2.60 1.80 1.40 Symbol L L1 θ b e e1 L1 ( REF.) Dimensions In Millimet ers Min Max 0.60 0.30 0.60 (REF) 10° 0° 0.38 0.22 0.65 (REF) 0.33 (REF) Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.1 9 PAM2810 4-Channel Programmable LED Current Sink Outline Dimensions DFN 2x2 D A B INDEX AREA (D/2 xE/2) E 4 TOP VIEW C A A1 9 8 SEATING PLANE SIDE VIEW 0.08 C e Nxb Pin#1 ID INDEX AREA (D/2 xE/2) NxL NxK E2 4 D2 BOTTOM VIEW SYMBOL A A1 Lead Pitch (e) 0.50 MIN 0.70 0.00 COMMON DIMENSION NOM MAX 0.75 0.80 0.02 0.05 Summary Table Lead Body Count Size 8 2X2 Pin #1 ID R0.20 D BSC E BSC MIN b NOM MAX MIN D2 NOM MAX MIN E2 NOM MAX MIN L NOM MAX N 2.00 2.00 0.18 0.25 0.30 1.05 1.20 1.30 0.45 0.60 0.70 0.20 0.30 0.40 8 Unit: Millimeters Power Analog Microelectronics , Inc www.poweranalog.com 08/2008 Rev 1.1 10