SLVAFO4 august   2023 TPS61299

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Overview
  5. 2Load Connected to Input Voltage
    1. 2.1 Body Diode Pass (TPS61288)
    2. 2.2 Force Pass Through (TPS61253)
    3. 2.3 Bypass (TPS61291)
    4. 2.4 Summary
  6. 3Load Disconnected to Input Voltage
    1. 3.1 Synchronous HSD FET With Switchable Body Diode (TPS61299)
    2. 3.2 Extra ISO FET to Cut-Off Leakage Path
  7. 4Summary
  8. 5References

3.2 Extra ISO FET to Cut-Off Leakage Path

A separated isolation MOSFET is needed in cases when the high side MOSFET cannot switch its body diode direction. The body diode cathode of the ISO-FET is connected to the input side. ISO FET is turned off when EN is low, completely cutting off the path between the input side and output side during shutdown and realizing true disconnection.

ISO FET can be placed both on output or input path. The TPS61378-Q1 is integrated with a separated N-MOS isolation FET on the output path as shown inFigure 3-3. The TPS61376 moves the separated N-MOS isolation FET to the input path as shown in Figure 3-4. In this case, the ISO FET can be reused as an inductor current sense FET. Therefore, the TPS61376 can program the input average current limit threshold. The shutdown waveforms of the TPS61378 and the TPS61376 is similar to Figure 3-2.

GUID-20230731-SS0I-KZGX-2WH1-B2DFST2KCZRD-low.svg Figure 3-3 TPS61378-Q1: ISO-FET on the output path
GUID-20230822-SS0I-ZQBW-6J8X-KX53FQPRWZZG-low.svg Figure 3-4 TPS61376: ISO-FET on the input path