a8837 Allegro MicroSystems, Inc., a8837 Datasheet
a8837
Related parts for a8837
a8837 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 A8837 is available in a very low profile (0.75 mm) 10-contact 3 mm × MLP/TDFN package, making it ideal for space-constrained applications lead (Pb) free, with 100% matte-tin leadframe plating ...
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... A8837 Selection Guide Part Number A8837EEJTR-T *Contact Allegro for additional packing options Absolute Maximum Ratings Characteristic SW pin IGBTDRV pin FB pin All other pins Operating Ambient Temperature Maximum Junction Temperature Storage Temperature Package Thermal Characteristics Characteristic Package Thermal Resistance *Additional information is available on the Allegro website. ...
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... Power supply input 4 GND Device ground Charging enable and ISWLIM code input; set to low to power-off 5 CHARGE the A8837 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 ¯ D ¯ ¯ O ¯ ¯ N ¯ ¯ E ¯ ...
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... A8837 ELECTRICAL CHARACTERISTICS Characteristics Supply Voltage* Supply Current Primary Side Current Limit (ILIM clock input at CHARGE pin Resistance SW Leakage Current* SW Maximum Off-Time SW Maximum On-Time CHARGE Input Current CHARGE Input Voltage* ILIM Clock High Time at CHARGE Pin ILIM Clock Low Time at ...
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... A8837 V UVLO VIN CHARGE SW Target V OUT V OUT DONE TRIGGER IGBTDRV A 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. ...
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... A8837 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 C2 V IGBTDRV C3 V TRIGGER ...
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... The control logic is shown in the functional block diagram. The charging operation of the A8837 is started by a low-to-high signal on the CHARGE pin, provided that V level. If CHARGE is already high before V another low-to-high transition on the CHARGE pin is required to start the charging ...
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... Figure 6 shows the last charging cycle, when the CHARGE pin is forced low before charging has been completed. The A8837 implements an adaptive off-time, t the switch is turned off, a sensing circuit tracks the flyback volt- age at the SW node. A special dV/dt detection circuit is used to allow minimum-voltage switching, even if the SW voltage does not drop to zero volts ...
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... A8837 Transformer Design The minimum transformer turns ratio, N, (Second- Turns Ratio. ary : Primary) should be chosen based on the following formula Drop OUT BATT where: (V) is the required output voltage level, V OUT (V) is the forward voltage drop of the output diode(s), ...
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... Ceramic capacitors with X5R or X7R dielectrics are recom- mended for the input capacitor, C2. It should be rated at least 4.7 μ decouple the battery input the transformer. When using a separate bias, V A8837 VIN supply, connect at least a 0.1 μF / 6.3 V bypass capacitor to the VIN pin. (3) Layout Guidelines ...
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... A8837 3.00 ±0. 11X 0.08 C +0.05 0.25 –0. 0.40 ±0.10 10 Copyright ©2008, 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 ...