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TPS7A4701-EP: LDO as a "load Switch"

Michael T Schneider
Expert 3780 points
Part Number: TPS7A4701-EP

Hey team, 

Are there any drawbacks or concerns using by the TPS7A4701 in following configuration:

Setting the output voltage (via resistors at feedback pin) at a setpoint that is greater than the input voltage?

The nominal condition would be Vin<Vout_setpoint and I would expect the internal FET to be fully saturated, therefore Vout≈Vin-Vdropout. For this application the customer is wanting the LDO to nominally pass the input voltage (like a load switch) but limit the output voltage when Vin>Vout_setpoint. could this work as long as the Vin is below the abs max ratings? 

  • +1
    TI__Genius 12040 points

    Hello Michael,

                          Please note that for this device, the pass element is a Bipolar PNP transistor and not a FET device. For the LDO to work as a switch, the key idea is to increase the Emitter- Base voltage differential to as large a value as possible to hard turn on the pass device. By increasing the output voltage (Collector of pass element), the Emitter-collector voltage differential is reduced, and I cant see how this would help the pass element act as a switch. The easiest way to convert the LDO to a load switch would be to connect the FB pin to GND. This would increase the Emitter- Base voltage differential of the pass element to the largest value possible. Thanks!

    Regards,

    Srikanth