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WEBENCH® Tools/TPS40170: TPS40170

Bob Ledoux
Prodigy 130 points
Part Number: TPS40170

Tool/software: WEBENCH® Design Tools

Hello, I am using the TPS40170 device in a new 48V to 8V buck configuration. I my application the output load capacitance is very high (5mF). The large amount of capacitance is bulk capacitance I added to help support servo current demands. The TPS40170 will not start up unless I reduce the capacitance substantially. Both the simulation and prototype board test show the TPS40170 start-up then continuously retry. Give the webench simulation also show the fault condition, I am currently modifying Ilim and soft start. I have not determined the correct settings yet.

Should I be able to start up with a capacitive 5mF load?

Can you please advise me on how to determine what soft-stat & Ilinit setting are needed?

Regards,

Bob Ledoux

Edgetech

  • 0
    TI__Guru**** 191445 points
    Basically, you are charging that 5 mF up to 8 V at a constant rate set by SS. the required current = I = (C*dV/dT) + load current = (5E-3 * 8 / Tss) + load current. You should set the SS time and current limit so that I stays below your current limit threshold. 5 mF does not seem excessively large.