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Original question:

LM5143: Why use logic level FETs for 58Vin, 600W Synchronous Buck?

LM5143: What purpose are D3/D4/D7/D8 in PMP31210

Ken Zhang
Expert 3545 points
Part Number: LM5143
Other Parts Discussed in Thread: PMP31210

Tool/software:

Hi, 

A my account has some questions about schematic of PMP31210. pls kindly help to check them.

  1. what purpose are D3/D4/D7/D8 Zener Diode? Can they be removed if peak voltage is lower than MOSFET's max. Vds?
  2. In current sense circuit, usually both R12 is same as R13. why are R12 and R13 different in the schematic?

         

  • +1
    TI__Guru 73072 points

    Hi Ken,

    1. D3 is an antiparallel Schlocky diode, which is sometimes installed in buck regulator designs to conduct during the deadtime. However, the deadtime is short with this controller (15ns), so no need to include this diode (see the EVM for example).

    2. R12 is the CS filter resistor. R13 should be not installed or 0Ω, as there is a bias current into the VOUT pin that can disturb the CS circuit.

    --

    Tim