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TPS4800Q1EVM: Riscp configuration - clarification on calculation and EVM configuration

Jacob Wyrick
Expert 8365 points
Part Number: TPS4800Q1EVM
Other Parts Discussed in Thread: TPS1200-Q1

Tool/software:

Hi team - We're trying to follow the short-circuit sizing for RISCP and we're having issues.

In the datasheet, we see the following equation:

When we modify the RISCP values on the EVM, the resistances aren't matching. For a 15A current limit with a 2mΩ shunt (2mOhm is on the EVM) I should be using a 5.5kΩ resistor, but the EVM is using a 10k. EVM schematic below:

Where are the 19mV and the 2µA in the datasheet equation are coming from? 

Why is the EVM using a 10kOhm resistor?

Thanks,

Jacob

  • +1
    TI__Mastermind 34935 points

    Jacob,

    This is a typo in the EVM documentation and we are working to correct it.  Originally, for the engineering silicon, the 19mV was 10mV which is where the 15A number is coming from. 2uA is an internally derived reference current, and 19mV is the comparator offset. 

    For the EVM configuration, 10k would get you approximately a 19.5A limit.

    You can use the design calculator for more of a concise calculation (it is same with TPS1200-Q1): https://www.ti.com/tool/download/TPS1200-Q1-CALC 

    Best Regards,
    Tim