IS31BL3230 8 CHANNELS CONSTANT CURRENT LED DRIVER WITH PWM BRIGHTNESS CONTROL February 2012 GENERAL DESCRIPTION The IS31BL3230 provides eight regulated current sources, each delivers up to 40mA of load current with careful selection of external sense resistors, all outputs at the IS31BL3230 may be connected in parallel to enable the current through the LED to be as high as 320mA. FEATURES Ultra low headroom voltage Cost effective LED driver Current adjustable via external resistors Best Noise and Efficiency Performance Highly integrated design, minimal component 1.6μA (typ.) Shutdown current Small package QFN-16 3mm×3mm The IS31BL3230 does not include a charge pump and therefore has no noise and significantly improved the efficiency. The external resistor, RSET1, determines the constant current output of ports LED1 thru LED4, while resistor RSET2 determines the constant current output of ports LED5 thru LED8. Brightness can be controlled with PWM techniques. The constant current source is set with two external sense resistors. APPLICATIONS Flash LED driver Backlight LED driver Alternatively, a PWM signal applied to the PWM pin can vary the perceived brightness of the LED. The device is in shut down mode when the PWM Input is logic low. TYPICAL APPLICATION CIRCUIT VIN Cin 1uF PWM ISET1 ISET2 RSET1 GND RSET2 Figure 1 Integrated Silicon Solution, Inc. – www.issi.com Rev.A, 01/05/2011 LED1 LED2 LED3 LED4 LED5 LED6 LED7 LED8 Typical Application Circuit 1 IS31BL3230 PIN CONFIGURATION 13 LED6 14 LED5 3 10 GND GND 4 9 8 VIN PWM 11 LED8 7 2 VIN LED1 6 12 LED7 ISET2 1 5 LED2 PWM QFN-16 15 LED4 Pin Configurations (Top View) 16 LED3 Package ISET1 PIN DESCRIPTION No. Name Description 1, 2, 11~16 LED1-LED8 Current source outputs 1~8. 3, 7 VIN Input voltage. 4, 10 GND Ground. 5, 8 PWM PWM brightness control. 6 ISET1 Current set1 input. 9 ISET2 Current set2 input. Copyright © 2011 Integrated Silicon Solution, Inc. All rights reserved. ISSI reserves the right to make changes to this specification and its products at any time without notice. ISSI assumes no liability arising out of the application or use of any information, products or services described herein. Customers are advised to obtain the latest version of this device specification before relying on any published information and before placing orders for products. Integrated Silicon Solution, Inc. does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless Integrated Silicon Solution, Inc. receives written assurance to its satisfaction, that: a.) the risk of injury or damage has been minimized; b.) the user assume all such risks; and c.) potential liability of Integrated Silicon Solution, Inc is adequately protected under the circumstances Integrated Silicon Solution, Inc. – www.issi.com Rev.A, 01/05/2011 2 IS31BL3230 ORDERING INFORMATION Industrial Range: -40°C to +85°C Order Part No. Package QTY/Reel IS31BL3230-QFLS2-TR QFN-16, Lead-free 2500 Integrated Silicon Solution, Inc. – www.issi.com Rev.A, 01/05/2011 3 IS31BL3230 ABSOLUTE MAXIMUM RATINGS Supply voltage, VIN -0.3V ~ +6.0V PWM -0.3V to (VIN+0.3V) / 6.0V Maximum junction temperature, TJMAX 150°C Storage temperature range, TSTG -65°C ~ +150°C Operating temperature range, TA −40°C ~ +85°C Note: 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 condition beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS Unless otherwise specified or noted, VIN = 3.6V, RSET=7.5kΩ, VLEDX=0.5V. Limits apply for TA=25°C. (Note) Symbol VIN Parameter Condition Supply Voltage Typ. 2.7 ILEDX Output Regulation VHR Minimum Headroom Voltage(LEDX) VSET ISET PIN Voltage Current Max Units 5.5 V 0.4V≤VLEDX≤2.0V, RSET = 7.5kΩ 16.0 mA RSET=7.5kΩ, ILEDX=20.0mA 44.0 mV 1.2 V 100.0 mA/mA 244.0 μA 1.6 μA ILEDX/ISET Output Current to Current Set Ratio IQ Quiescent Supply Current ILEDX=0mA, ISET=Float IPWM Shutdown Supply Current PWM=0 VPWM-IH PWM Input Logic High 3.0V≤VIN≤5.5V VPWM-IL PWM Input Logic Low 3.0V≤VIN≤5.5V PWM Pin Current V(PWM) = 1.5V IPWM Min 1.4 V 0.4 5.6 V μA Note: Production testing of the device is performed at 25°C. Functional operation of the device and parameters specified over other temperature range, are guaranteed by design, characterization and process control. Integrated Silicon Solution, Inc. – www.issi.com Rev.A, 01/05/2011 4 IS31BL3230 TYPICAL PERFORMANCE CHARACTERISTICS 45 RSET = 3.0kΩ VIN = 3.3V 40 RSET = 4.0kΩ 30 25 RSET = 6.0kΩ 20 RSET=6.0k LED Current (mA) LED Current(mA) 35 RSET = 7.5kΩ 15 RSET=7.5k RSET=12.0k RSET = 12.0kΩ 10 VIN=3.3V VLEDX=0.2V 5 0 0 50 100 150 200 Output Voltage(VLEDX)(mV) Figure 2 290 Power Supply(V) Output Voltage vs. LED Current RSET = 7.5kΩ Power Supply vs. LED Current VIN = 3.3V 40 280 35 270 LED Current(mA) Quiescent Current(µA) Figure 3 45 260 250 240 30 25 20 15 10 230 220 5 3 3.5 4 4.5 5 0 3 8 Power Supply(V) Figure 4 Power Supply vs. Quiescent Current Integrated Silicon Solution, Inc. – www.issi.com Rev.A, 01/05/2011 13 18 23 28 30 RSET(kΩ) Figure 5 RSET vs. LED Current 5 IS31BL3230 APPLICATION INFORMATION CIRCUIT DESCRIPTION The IS31BL3230 is a white-LED driver with eight matched current outputs. The matched current regulators each has a 100:1 current ratio between the LEDX outputs and the ISET currents. The mirror controls the current through the LEDs without the use of external ballast resistors. With a total of 320mA of total output current available, the IS31BL3230 is capable of providing 40mA to each of the eight outputs through the proper selection of the RSET1 & RSET2 resistor. LED brightness control can be achieved on the IS31BL3230 with PWM signal. SHUTDOWN When the voltage on the active-high-logic PWM pin is low, the IS31BL3230 will be in shutdown mode. While disabled, the IS31BL3230 typically draws 1.6μA form the power supply. There is no internal pull-up or pull-down on the PWM pin of the IS31BL3230. OUTPUT CURRENT CAPABILITY The IS31BL3230 can provide up to 40mA of current to each of the eight outputs given an input voltage of 2.7V to 5.5V. An external resistor can be used to set the output current, as approximated with the following the equation: RSET1, 2=100 × (VISET1, 2 / ILEDX ) RSET1 determines the constant current output of ports LED1 thru LED4, RSET2 determines the constant current output of ports LED5 thru LED8, VISET is the voltage of RSET resistance, it is 1.20V typically. In order for the output currents to be regulated properly, sufficient headroom voltage (VHR) is required. The headroom voltage refers to the minimum amount of voltage that must be present across the current source in order to ensure the desired current is realizable. To ensure the desired current is obtained, using the following equations to find the minimum input voltage required: VIN - VLEDX ≥ VHR VLEDX is the diode forward voltage; VHR is typically as shown in table1. Table1. ILED, RSET and VHR-MIN, VCC=3.3V ILED RSET VHEADROOM 10.0mA 12.0kΩ 27 mV(typ.) 16.0mA 7.5kΩ 44 mV(typ.) 20.0mA 6.0kΩ 53 mV(typ.) 30.0mA 4.0kΩ 66 mV(typ.) 40.0mA 3.0kΩ 75 mV(typ.) PWM BRIGHTNESS CONTROL Brightness control can be implemented by pulsing a signal at the PWM pin. Integrated Silicon Solution, Inc. – www.issi.com Rev.A, 01/05/2011 The RSET value should be 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 turn-on time (TON=50μs) of the device. D × (1/f) > TON fMAX = DMIN / TON If the PWM frequency is much less than 100Hz, flicker may be seen in the LEDs. For the IS31BL3230, 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 16mA, a 50% duty cycle will result in an average ILED of 8mA, ILED being half the programmed LED current. RSET should be chosen not to exceed the maximum current delivery capability of the device. LED SELECTION The IS31BL3230 has ultra low headroom voltage and it is designed to drive white-LEDs with a typical forward voltage up to 3.5V. As the voltage drop below the recommend VHR, the drive current will automatically scale down to reduce the LED current consumption. POWER DISSIPATION The maximum allowable power dissipation that this package can handle is determined by the following: PDMax = (TJMax - TA) /θJA Where TJMAX is the maximum junction temperature, TA is the ambient temperature and θJA is the junction-to-ambient thermal resistance of the specified package. The IS31BL3230 come in the QFN-16 3mm×3mm package, and it has a junction-to-ambient thermal resistance （θJA） equal to 34.5°C/W. This value of θJA is highly dependant upon the layout of the PC board. The actual power dissipated by the IS31BL3230 follows the equation: PDISS = (VIN ×ICC) - N(VLEDX × ILEDX) Where N equals the number of active outputs, VLEDX is the LED forward voltage, and ILEDX is the current supplied to the LED. INPUT CAPACITOR SELECTION The IS31BL3230 is designed to run off of a fixed input voltage. Depending on the stability and condition of this voltage rail, it may be necessary to add some small input capacitors to help filter out any noise that may be present on the line. In the event that filtering is needed, surface-mount multi-layer ceramic capacitors are recommended. These capacitors are small and inexpensive. Two capacitances, a 0.1μF and a 1μF are typically sufficient. 6 IS31BL3230 CLASSIFICATION REFLOW PROFILES Profile Feature Pb-Free Assembly Preheat & Soak Temperature min (Tsmin) Temperature max (Tsmax) Time (Tsmin to Tsmax) (ts) 150°C 200°C 60-120 seconds Average ramp-up rate (Tsmax to Tp) 3°C/second max. Liquidous temperature (TL) Time at liquidous (tL) 217°C 60-150 seconds Peak package body temperature (Tp)* Max 260°C Time (tp)** within 5°C of the specified classification temperature (Tc) Max 30 seconds Average ramp-down rate (Tp to Tsmax) 6°C/second max. Time 25°C to peak temperature 8 minutes max. Figure 6 Classification Profile Integrated Silicon Solution, Inc. – www.issi.com Rev.A, 01/05/2011 7 IS31BL3230 TAPE AND REEL INFORMATION Integrated Silicon Solution, Inc. – www.issi.com Rev.A, 01/05/2011 8 IS31BL3230 PACKAGE INFORMATION QFN-16 Note: All dimensions in millimeters unless otherwise stated. Integrated Silicon Solution, Inc. – www.issi.com Rev.A, 01/05/2011 9