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Original question:

TPS43061: MOSFET Selection

TPS43061: About high side MOSFET

Ryoma Ohashi
Expert 4500 points
Part Number: TPS43061

Hi team, 

My customer is trying to use TPS43061 and have 2 questions about the high side FET.

  1. In general boost converter, normal diodes are used for high side rectification. But for this device, MOSFET are use for synchronous rectification which enables high-efficiency for high-current applications. And in the datasheet, it says that  "In a boost topology, the input is passed to the output through the inductor and high-side FET body diode." Could you explain all the function of this high side MOSFET and why it helps to higher the efficiency?
  2. Can this high side MOSFET be substituted by a normal diodes?

Regards,

Ohashi

  • 0
    TI__Guru 55221 points

    Hi Ohashi,

    thank you for using the E2E forum.

    1. A Diode has voltage drop of 0.7 V or 0.3. in case of a Schottky diode. Whereas an MOSFET only has the drop over R_DS,on when switched on. So the loss is typically less on a MOSFET compared to a Diode. But also a MOSFET has a Body Diode which will give pass through path if the MOSFET has not been switched on (see the symbol of a MOSFET where the Body diode is normally shown.

    2. In this case you should use an asynchronous controller as this as designed for that mode. May check the LM515x devices.

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    TI__Expert 4500 points

    If the MOSFET is controlled to do a synchronous rectification and turn on complementary with the low side FET, is there a situation that the MOSFET is turned off but current goes through the body diode?

    If so, how can this device achieve such high efficiency?

  • +1 in reply to Ryoma Ohashi
    TI__Guru 55221 points

    Hi Ryoma,

    please check the datasheet section:

    8.4.2 Pass Through (VIN > VOUT)

    Best regards,

     Stefan