A8436 ALLEGRO [Allegro MicroSystems], A8436 Datasheet
A8436
Available stocks
Related parts for A8436
A8436 Summary of contents
Page 1
... Li+ battery connected to the transformer primary. Connect the VIN pin to a 3.0 to 5.5 V supply, which can be either the system rail or the Li+ battery, if used. The A8436 is available in a very low profile (0.75 mm) 10- terminal 3×3 mm MLP/TDFN package, making it ideal for space-constrained applications lead (Pb) free, with 100% matte-tin leadframe plating ...
Page 2
... Description (continued) Applications include: ▪ Digital camera flash ▪ Film camera flash ▪ Cell phone flash ▪ Emergency strobe light Selection Guide Part Number A8436EEJTR-T *Contact Allegro for additional packing options Absolute Maximum Ratings Characteristic SW pin IGBTDRV pin FB pin All other pins ...
Page 3
... IGBT driver gate drive output 3 VIN Power supply input 4 GND Device ground 5 CHARGE Charging enable; set to low to power-off the A8436 6 SW Switch, internally connected to the DMOS power FET drain 7 TRIGGER Strobe signal input Open drain, when pulled low by internal MOSFET, indicates that 8 ¯ ...
Page 4
... A8436 ELECTRICAL CHARACTERISTICS Characteristics Supply Voltage* Supply Current Primary Side Current Limit SW On Resistance SW Leakage Current* SW Maximum Off-Time SW Maximum On-Time CHARGE Input Current CHARGE Input Voltage* ¯ D ¯ ¯ O ¯ ¯ N ¯ ¯ E ¯ Output Leakage Current* ¯ D ¯ ¯ O ¯ ¯ N ¯ ¯ E ¯ Output Low Voltage* ...
Page 5
... A8436 V UVLO VIN CHARGE SW Target V OUT V OUT DONE TRIGGER IGBTDRV Explanation of Events: A. Start charging by pulling CHARGE to high, provided that V B. Charging stops when V completion of the charging process. C. Start a new charging process with a low-to-high transition at the CHARGE pin. D. Pull CHARGE to low, to put the controller in low-power standby mode. ...
Page 6
... A8436 Tests performed using application circuit shown in figure 6 (unless otherwise noted) Charging Waveforms Symbol Parameter Units/Division C1 V OUT C4 I BATT(Avg) t time Conditions Parameter V BATT V BIAS C OUT Symbol Parameter Units/Division C1 V OUT C4 I BATT(Avg) t time Conditions Parameter V BATT V BIAS C OUT Symbol Parameter Units/Division ...
Page 7
... A8436 Performance Characteristics, continued Tests performed using application circuit shown in figure 6 (unless otherwise noted) Charge Time BIAS Connect VBATT to a separate power supply 320 V V OUT = 320 V OUT 300 V OUT V = 300 V OUT 2.0 2.5 3.0 3.5 2 2.5 3 3.5 4 ...
Page 8
... A8436 Performance Characteristics, continued IGBT Drive waveforms are measured with R-C load (12 Ω, 6800 pF) Rising Signal Symbol Parameter Units/Division C2 V IGBTDRV C3 V TRIGGER t time 50 ns Conditions Parameter Value t 22.881 63.125 6800 pF LOAD R 12 Ω gate Falling Signal Symbol Parameter Units/Division ...
Page 9
... IN UVLO mode is a fixed 18 μs off-time control. One advantage of the A8436 watchdog timer control scheme is that it limits the initial current surge and thus acts as a “soft-start.” As shown in figure 3, , ramps up linearly at a the timer mode only lasts a small fraction of a second (usually < ...
Page 10
... I goes discontinuous, leading to Secondary the ringing The amplitude of the SW ringing is not great enough, however, to pull V below 1 the A8436 SW remains in Timer mode. Figure 4C. The final cycle of Timer mode is shown, followed by a series of cycles in Fast Charging mode able to ring SW down below 1 every cycle as a result ...
Page 11
... L is the primary side inductance, and Primary N is the transformer turns ratio (N Secondary As shown in the three panels of figure 4, when the A8436 charges a fully-discharged photoflash capacitor, I slowly due to the low initial V . The A8436 internal timer OUT (Timer mode) sets a maximum timeframe of 18 μs for the off- time as long as the SW node voltage is greater than 1.2 V. When the off-time passes 18 μ ...
Page 12
... In practice, always choose a turns ratio that is higher than the calculated value to give some safety margin. In the worst case example, a minimum turns ratio recommended. . The A8436 has a minimum switch off-time, Primary Inductance 300 ns, to ensure correct SW node voltage sensing. ...
Page 13
... C2. It should be rated at least 4.7 μ decouple the battery input the transformer. When using a separate bias, V A8436 VIN supply, connect at least a 0.1 μF / 6.3 V bypass capacitor to the VIN pin. Layout Guidelines Key to a good layout for the photoflash capacitor charger circuit is to keep the parasitics minimized on the power switch loop (transformer primary side) and the rectifier loop (secondary side) ...
Page 14
... A8436 Preliminary dimensions, for reference only (reference JEDEC MO-229 WEED) Dimensions in millimeters U.S. Customary dimensions (in.) in brackets, for reference only Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A Terminal #1 mark area ...