a8735 Allegro MicroSystems, Inc., a8735 Datasheet
a8735
Related parts for a8735
a8735 Summary of contents
Page 1
... The charge and trigger voltage logic thresholds are set (min) to support applications implementing low-voltage HI control logic. The A8735 is available in an 8-contact 2 mm × DFN/MLP package with a 0.60 maximum overall package height, and an exposed pad for enhanced thermal performance lead (Pb) free with 100% matte tin leadframe plating. Typical Applications ...
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... A8735 Selection Guide Part Number Packing A8735EEETR-T 3000 pieces per reel Absolute Maximum Ratings Characteristic Symbol V SW Pin VIN_DRV, VBAT Pins CHARGE, TRIG, ¯ D ¯ ¯ O ¯ ¯ N ¯ ¯ E ¯ Pins Remaining Pins Operating Ambient Temperature Maximum Junction T J Storage Temperature ...
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... A8735 VBAT V – BAT ILIM Reference V ref DS VIN_DRV CHARGE TRIG Pin-out Diagram DONE 1 8 CHARGE TRIG 2 7 VIN_DRV PAD GATE 3 6 VBAT GND (Top View) Ultra Small Mobile Phone Xenon Photoflash Capacitor Charger with IGBT Driver Functional Block Diagram ...
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... A8735 ELECTRICAL CHARACTERISTICS guaranteed from −40°C to 85°C ambient, unless otherwise noted Characteristics 1 VBAT Voltage Range 1 VIN_DRV Voltage Range UVLO Enable Threshold UVLO Hysteresis V Supply Current IN VBAT Pin Supply Current Current Limit Primary-Side Current Limit 2 Switch On-Resistance 1 Switch Leakage Current ...
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... A8735 VBAT UVLO V IN CHARGE SW Target V V OUT DONE TRIG GATE Explanation of Events A: Start charging by pulling CHARGE to high, provided that V B: Charging stops when V C: Start a new charging process with a low-to- D: Pull CHARGE to low to put the controller in low-power standby mode. E: Charging does not start, because V F: After V start the charging ...
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... A8735 IGBT drive waveforms are measured at pin, with capacitive load of 6800 pF Rising Signal Symbol Parameter Units/Division TRIGGER GATE time 100 ns Conditions Parameter Value 320 6.8 nF LOAD Falling Signal Symbol Parameter Units/Division ...
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... A8735 Transformer L PRIMARY Transformer L 86% 84% 82% 80% 78% 76% 74% 72% 70% 68% 66% 64% 62% 60% 58% 56% 54% Ultra Small Mobile Phone Xenon Photoflash Capacitor Charger with IGBT Driver Characteristic Performance Charge Time versus Battery Voltage = 12.8 μH, N =10.25 OUT 1.5 2.0 2.5 3.0 3.5 4.0 Battery Voltage (V) Efficiency versus Battery Voltage = 12.8 μ ...
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... A8735 Transformer L 328 327 326 325 324 323 322 321 320 Note: Output voltage is sensed from the primary side winding when the switch turns off. This duration long enough (>200 ns) in order to obtain an accurate measurement. The value of t primary inductance, L Transformer L 0 ...
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... A8735 Output Capacitor Charging at Various Battery Voltages Test conditions 3 100 μF / 330 V UCC, transformer = T-16-024A (L IN OUT Oscilloscope settings: Ch1 = ¯ D ¯ ¯ O ¯ ¯ N ¯ ¯ E ¯ div), Ch2 = Battery Voltage ( div), Ch3 = Output Voltage ( div), Ch4 = Input Current (100 div), ...
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... Ultra Small Mobile Phone Xenon Photoflash Capacitor Charger with IGBT Driver Functional Description Timer Mode and Fast Charging Mode The A8735 achieves fast charging times and high efficiency by operating in discontinuous conduction mode (DCM) through level UVLO most of the charging process. The relationship of Timer mode and Fast Charging mode is shown in figure 2 ...
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... A8735 As soon as a sufficient voltage has built up at the output capaci- tor, the IC enters Fast-Charging mode. In this mode, the next switching cycle starts after the secondary side current has stopped flowing, and the switch voltage has dropped to a minimum value. A proprietary circuit is used to allow minimum-voltage switch- ing, even if the SW pin voltage does not drop ...
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... A8735 Transformer Design 1. The transformer turns ratio, N, determines the output voltage 31.5 × N – OUT d where 31.5 is the typical value of V OUTTRIP ward drop of the output diode. 2. The primary inductance determines the on-time of PRIMARY the switch: = (– × – I ...
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... BAT Figure 9. Input current waveforms with Li+ battery connected through 4.7 μH inductor and 4.7 μF capacitor calculated as: DPeak Ch1: V OUT / s/div C2 A8735 C3 C1 Figure 10. Input current waveforms with Li+ battery connected through , may IN 4.7 μH inductor and 10 μF capacitor, C Ch1: V OUT s/div Effects of Input Filters = 100 μ ...
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... A8735 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). Use short, thick traces for connections to the transformer primary and SW pin important that the ¯ D ¯ ¯ ¯ O ¯ ¯¯ N ¯ ¯ E ¯ signal trace and other signal traces be routed away from the transformer and other switching traces, in order to minimize noise pickup ...
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... A8735 Recommended layout: C4 Schematic 0.1uF DONE CHARGE Top side Bottom side Top components Ultra Small Mobile Phone Xenon Photoflash Capacitor Charger with IGBT Driver VBAT C2 10uF R10 6 5 A8735 2k VBAT VIN_DRV GATE 1 2 DONE TRIG 8 4 CHARGE GND C5 1nF U1 TRIGGER ...
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... A8735 Package EE 8-Contact DFN/MLP with Exposed Thermal Pad D 9X 0.08 C 0.25 ±0.05 0.325 ±0.050 Copyright ©2010, Allegro MicroSystems, Inc. The products described here are manufactured under one or more U.S. patents or U.S. patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec tions as may be required to per- mit improvements in the per for mance, reliability, or manufacturability of its products ...