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INA300-Q1: low-pass filtering inputs to INA300-Q1

Forrest Smith
Prodigy 10 points
Part Number: INA300-Q1

I am applying the OCP chip with a 28V high-side source and a 10 milli-ohm shunt.

- if I am implementing the low-pass input filtering scheme from Figure 30 of the data sheet, is there a limitation on the value of CFILTER?   I am planning to use the filter to permit the OCP chip to ignore starting inrush current to the load that far exceeds the setpoint threshold.   Is it OK to have as much as 20 μF to 100 μF on the CFILTER, as the series RFILTER resistors are limited to 100 ohms?  I do not see anything about the value of CFILTER in the datasheet.

-  if I need the large capacitance for CFILTER, for space reasons this seems like an ideal application for a low-voltage tantalum polymer capacitor.  The cap will only see a few hundred millivolts even from the inrush current.  The typical will be 25 mV.   I am contemplating using a 6.3V 100 μF tantalum poly capacitor with a paralleled 0.01 μF ceramic cap for noise rejection.  Does this seem like a good plan? 

  • 0
    TI__Mastermind 30720 points

    Hi,

    There is no limit on how big the filter cap can be. However in general you would want one with low leakage, so that a decent voltage versus time ramp is maintained. Since the charge current of 20uA is fairly large, I guess most likely it is OK. But it is something to keep in mind when it comes to pick the specific capacitor. The tantalum cap can have relatively large leakage comparing to other types.

    The follow-on question is then, how do you plan to set the delay in normal operation? Do you plan to switch out the large cap and leave behind a smaller one? Just something to think about.

    Regard, Guang