+ A8835 Photoflash Capacitor Charger with Programmable Current Limit and IGBT Driver Features and Benefits Description Eight-level, digitally-programmable current limits from The A8835 is a highly integrated IC that charges photoflash 550 mA to 1.75 A capacitors for digital and film cameras. An integrated MOSFET Voltage sensing feedback before output diode for low switch drives the transformer in a flyback topology. It also leakage features an integrated IGBT driver that facilitates the flash No external pull-down resistors needed discharge function and saves board space. Power with 1 Li+ or 2 Alkaline/NiMH/NiCAD batteries The CHARGE pin enables the A8835 and starts the charging Low quiescent current draw (1 A max in shutdown mode) of the output capacitor. When the designated output voltage is Zero-voltage switching for lower loss reached, the A8835 stops the charging until the CHARGE pin Adjustable output voltage is toggled again. The DONE pin is an open-drain indicator of Integrated IGBT driver with trigger when the designated output voltage is reached. Charge complete indication >75% efficiency The peak current limit can be adjusted to eight different levels Low-profile (0.75 mm high) 3 mm 3 mm TDFN between 550 mA and 1.75 A, by clocking the CHARGE pin. 10-contact package This allows the user to operate the flash even at low battery voltages. Applications: The A8835 can be used with two Alkaline/NiMH/NiCAD or one single-cell Li+ battery connected to the transformer primary. Digital camera flash Cell phone flash Connect the VIN pin to a 3.0 to 5.5 V supply, which can be Film camera flash Emergency strobe light either the system rail or the Li+ battery, if used. The A8835 is available in a very low profile (0.75 mm) Package: 10-contact TDFN with exposed 10-contact 3 mm 3 mm TDFN package, making it ideal for space-constrained applications. It is lead (Pb) free, with thermal pad (suffix EJ) 100% matte-tin leadframe plating and has an exposed pad for enhanced thermal dissipation. Approximate Scale Typical Applications V 1.5 to 5.5 V N =10.2 V 3.0 to 5.5 V BATT V BIAS D1 3.0 to 5.5 V T1 D1 BIAS V OUT V OUT T1 R1 R1 COUT CIN 150 k 7 C1 CIN 100 F 150 k 7 R4 4.7 F COUT C1 1% 0.1 F 4.7 F 100 k 7 330 V R4 0.1 F 100 k 7 R2 R2 150 k 7 150 k 7 1% VIN VIN SW SW CHARGE CHARGE FB FB A8835 R3 A8835 R3 1.20 k 7 1.20 k 7 1% DONE DONE TRIGGER IGBTDRV TRIGGER IGBTDRV To IGBT Gate GND To IGBT Gate GND Figure 2. Typical circuit with single power supply Figure 1. Typical circuit with separate power supply to transformer A8835-DS, Rev. 1Photoflash Capacitor Charger A8835 with Programmable Current Limit and IGBT Driver Selection Guide Part Number Package Packing* A8835EEJTR-T 10-pin TDFN 1500 pieces/ 7-in. reel *Contact Allegro for additional packing options Absolute Maximum Ratings Characteristic Symbol Notes Rating Units DC voltage. (V is self-clamped by an internal SW active clamp and is allowed to exceed 40 V dur- SW pin V ing flyback spike durations. Maximum repetitive 0.3 to 40 V SW energy during flyback spike: 0.5 J at frequency 400 kHz.) IGBTDRV pin V 0.3 to V + 0.3 V IGBTDRV IN FB pin V 0.3 to V V FB IN All other pins V 0.3 to 7 V X Operating Ambient Temperature T Range E 40 to 85 C A Maximum Junction Temperature T (max) 150 C J Storage Temperature T 55 to 150 C stg Package Thermal Characteristics Characteristic Symbol Test Conditions* Rating Units Package Thermal Resistance R On 4-layer PCB, based on JEDEC standard 45 C/W JA *Additional information is available on the Allegro website. Allegro MicroSystems, Inc. 2 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com