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TPS40090: Design for a synchronous buck

user5137167
Prodigy 70 points
Part Number: TPS40090

Hi,

I am designing a 3 phase synchronous buck DC/DC converter with 36 V input voltage and 24 V output voltage. The maximum output power is 5kW.

Here is my question:

1. What is the maximum voltage of PIN COMP when the output voltage does not reach the reference? If I need to limit the maximum output current to 115% of the rated current, how can I limit the voltage of PIN COMP?

2. According to the application diagram in the datasheet, PIN EN/SYNC is connected to nothing. Can PIN EN/SYNC be connected to PIN VIN by a resistor (1k) to enable?

Thank you!

  • 0
    TI__Mastermind 24075 points

    Helo,

    1. The controller does not use COMP voltage for OC protection. Instead, it compares current sense input voltage (the voltage between CSx and CSCN) with ILIM pin voltage for OC protection. Detailed information can be found on datasheet page 11.

    2. Keep EN/SYNC pin voltage below 15V. It is fine to connect EN pin to VIN pin via pull-up resistor if VIN pin voltage is below 15V. Otherwise, connect EN pin to VIN pin through resistor divider.

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Prodigy 70 points
    Hi,
    Thank you for the suggestion, but I did not mean OC protection. When the load resister is very small, the output current of the converter needs to be limited to 115% of the rated current, and the output voltage can decrease. That is to say, when the load is too heavy, the converter needs to operate in constant-output-current mode, not constant-output-voltage mode. Therefore, I need to limit the voltage of PIN COMP to limit the maximum output current.
    Thanks!
  • 0 in reply to user5137167
    TI__Mastermind 24075 points
    To achieve constant output current mode, an external error amplifier is needed to limit the COMP voltage at OC condition.
    For easy communication, can we discuss by email?
    Q-CHEN@TI.COM