PDF IS31BL3233A Data sheet ( Hoja de datos )

Número de pieza	IS31BL3233A
Descripción	1.5A FLASH/TORCH LED DRIVER
Fabricantes	ISSI
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No Preview Available ! IS31BL3233A 2MHz, 1.5A FLASH/TORCH LED DRIVER Preliminary Information September 2014 GENERAL DESCRIPTION The IS31BL3233A is the ideal power solution for high-power flash LEDs used with cell phone camera modules or digital still cameras. It is a highly integrated step up DC-DC converter with very high switching frequency, fixed at 2MHz, providing a very small total solution for portable photo flash. The IS31BL3233A has separate Flash Mode and Torch Mode enable pins for maximum flexibility. The Flash Mode and Torch Mode LED current is programmed by external resistors respectively, making the flash LED solution simple to control. If both enable pins are at logic high, the LED current will be programmed by the Torch Mode setting resistor. The two LED output sinks can be shorted together externally for higher power single flash LEDs, up to 1.5A continuous LED current. Thermal regulation is integrated in Flash Mode to limit the IC’s temperature and continuously provide the maximum allowed output current. Various protection features are built into the IS31BL3233A, including cycle-by-cycle input current limit protection, output over-voltage protection, LED fault (open or short) protection and thermal shutdown protection. The IS31BL3233A is available in a RoHS compliant DFN-14 (2mm × 3mm) package. FEATURES  Input voltage range: 2.7V~5.5V  Dual flash LED outputs  Drive up to total 1.5A or 0.75A per channel  1s time out in Flash Mode to protect LED  High efficiency up to 93% (1A, Flash Mode)  2MHz step-up converter  Independent Flash Mode enable and Torch Mode enable pins  Torch Mode dimming via PWM control  Integrated thermal regulation control  LED open/short protection  Over-voltage protection  Cycle-by-cycle inductor current limit  Pb-free package: DFN-14 (2mm×3mm)  -40C° ~ +85C° temperature range APPLICATIONS  Mobile phones  Smart phones and PDAs  Digital still cameras TYPICAL APPLICATION CIRCUIT Figure 1 Typical Application Circuit (Torch Mode current is100mA and Flash Mode current is 500mA) Integrated Silicon Solution, Inc. – www.issi.com Rev. 0C, 09/11/2014 1 1 page IS31BL3233A ABSOLUTE MAXIMUM RATINGS Supply voltage, VCC Voltage at any input pin Maximum junction temperature, TJMAX Storage temperature range, TSTG Operating temperature range, TA ESD (HBM) ESD (CDM) -0.3V ~ +6.0V -0.3V ~ VCC+0.3V 150°C -65°C ~ +150°C −40°C ~ +85°C 8kV 1kV 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 The following specifications apply for VCC = 3.6V, TA = 25°C, unless otherwise noted. Symbol Description Condition Min. Typ. Max. Units IC Supply VCC UVLO UVLOHYST Input operating range Input under voltage lockout UVLO hysteresis ICC Operating current ISD Shutdown current Step-Up Converter ILIM fSW DMAX VOVP tS Peak NMOS current limit Oscillator frequency Maximum duty cycle Internal over voltage threshold of VOUT Flash mode soft start time Current Sink Total output current, Torch Mode IOUT Total output current, Flash Mode ∆IOUT Output current matching (Note 2) ISHORT LED short checking current Rising edge Not switching (RSETM = 135kΩ) Switching (RSETM = 135kΩ) VENF = VENM = GND RSETF = 9.1kΩ (Note 1) VENM = VCC, RSETM = 135kΩ, D1+D2 VENF = VCC = 3.8V, VENM = GND, RSETF = 9.1kΩ, D1+D2 50mA/CH 750m/CH 2.7 5.5 V 2.1 2.4 2.68 V 0.2 V 1.0 1.5 mA 1.8 2.6 mA 0.1 1 µA 3A 2.0 MHz 75 % 5.3 V 100 µs 90 100 110 mA 1.305 1.5 1.695 A 2 10 % 2 10 % 3.5 mA Integrated Silicon Solution, Inc. – www.issi.com Rev. 0C, 09/11/2014 5 5 Page IS31BL3233A LED SHORT PROTECTION When the IS31BL3233A is enabled, there is a 2.5mA (Typ.) LED sensing current through each current sink. It is used to detect whether either LED is shorted by generating a voltage drop through each LED. The IC internally compares the voltage difference between VOUT and each sink node (D1 and D2). If this difference is below a preset threshold (Typ. 1.7V), the IC will treat the respective LED as shorted and disable its Flash/Torch Mode current through this LED channel. However, the 2.5mA sensing current will be kept to generate the LED’s voltage drop. If the short circuit is removed during operation, the channel will automatically recover to the programmed current setting. LED OPEN PROTECTION In case of LED open, the open channel will control the loop first so that VOUT will reach OVP, then IS31BL3233A will automatically detect which channel’s LED is open and disable that channel. From that point, the other channel with properly operating LED will control the loop and VOUT will be regulated down to a normal operating voltage. This protection feature avoids unnecessary power consumption in the current sink by regulating the output voltage at the lowest level possible to maintain regulation for the active channel. Not only does this protect from open LEDs failures, but also allows only single flash LED operation with the unused channel floating or open. Open-circuit LED fault protection is reset when the IC is powered down and up again. INDUCTOR SELECTION The IS31BL3233A is designed to use a 1.0μH to 4.7μH inductor. To prevent core saturation, ensure that the inductor-saturation current rating exceeds the peak inductor current for the application. The worst-case peak inductor current can be calculated with the following formula: I PEAK( L)  V  IOUT(MAX) LED(MAX) 0.8 VIN(MIN)  VIN(MIN)  tON(MAX) 2L where 0.8 is the estimated efficiency of 80%. (3) For example, for a 1.0A total (or 0.5A per channel) LED current, the peak inductor current for a 1.0uH inductor could be as high as (estimated 50% as the maximum duty ratio at the minimum input voltage, maximum LED forward voltage and maximum load current conditions): I PEAK(L)  4V 1A 0.8  3.5V  3.5V 0.25 21  1.9 A If the inductor value is smaller, the inductor peak current will increase. To maintain stable operations for the boost converter, the inductor peak current must be less than both the IS31BL3233A current limit threshold and the inductor saturation current rating. Manufacturer’s specifications of inductors list both the inductor DC current rating, which is a thermal limitation, and peak inductor current rating, which is determined by the saturation characteristics. Measurements at full load and high ambient temperature should be performed to ensure that the inductor does not saturate or overheat due to its parasitic resistance. Bench measurements are recommended to confirm actual inductor peak current IPEAK and to ensure that the inductor does not saturate at maximum LED current and minimum input supply voltage. CAPACITOR SELECTION For good input voltage filtering low ESR ceramic capacitors are recommended. At least a 2.2μF input capacitor is recommended for high current flash LEDs to improve transient behavior of the regulator and EMI behavior of the total power supply circuit. The input capacitor should be placed as close as possible to the input pin and the PGND pin of the IS31BL3233A. The output capacitance required depends on the required LED current. A 4.7μF ceramic capacitor works well in most situations, but a 1.0μF capacitor is acceptable for lower LED current conditions. PCB LAYOUT Due to the fast switching transitions and high-current paths, careful PC board layout is required. Connect AGND pin directly to the exposed paddle underneath the IC; connect the exposed paddle to the PCB ground plane. The output bypass capacitor should be placed as close to the IC as possible. Minimize trace lengths between the IC and the inductor, the input capacitor, and the output capacitor; keep these traces short, direct, and wide. The ground connections of CIN and COUT should be as close together as possible and connected to PGND. Integrated Silicon Solution, Inc. – www.issi.com Rev. 0C, 09/11/2014 11 11 Page

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