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LTC4353

Hi,

We designed a little circuit to select between 2 voltage source with the LTC4353 but we don't have the result expected.

We want to be able to shutdown Vout and select Vin2 if present instead of Vin1(always present) but Vin1>Vin2

Vin1 = 7.4V battery

Vin2 = 5V usb

Enable1 connected to a microcontroller as shutdown signal.

When no usb connected we have Vout =7.4V = Vin1 but if we put 5V on Enable1(Present only on EN2) we still have voltage at Vout and we shouldn't, should be cut

When the USB is connected we have 5V on EN1 but we still have Vout = 7.4V = Vin1 instead of 5V

Does the circuit allow the biggest voltage even if we don't drive the mosfet because of the internal diode?

Can we avoid that?

Does an other circuit will work better for our goal?

Parents
  • Hi,  Yes, due to the MOSFET's internal body diode, Vin1 can never be completely cut off from output. It requires back-to-back FETs but LTC4353 doesn't work with back-to-back FETs. LTC4352 (single) works with back-to-back FETs. This is a prioritized supply application, so consider LTC4418 and LTC4421, both 2-channel prioritizers.

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  • Hi,  Yes, due to the MOSFET's internal body diode, Vin1 can never be completely cut off from output. It requires back-to-back FETs but LTC4353 doesn't work with back-to-back FETs. LTC4352 (single) works with back-to-back FETs. This is a prioritized supply application, so consider LTC4418 and LTC4421, both 2-channel prioritizers.

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