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Original question:

TPS2121: Current Limiter

TPS2121: Current Limiting Variation - below 1 A

Srdjan Najhart
Prodigy 40 points
Part Number: TPS2121

Hello,

According to the spec sheet the current limit on the TPS2121 varies +/- 0.5 A. There is an equation used to calculate the current limit based on the current limiting resistor used [ I = 65.2 / (R^0.861) ]. I have used various resistors including those greater than 100 K to get current limits below 1 A and the measured current limit is very close to the calculated value (within 100 mA). The current limit also does not vary much with temperature (-40 to +85 C) and between the 2 chips I tested.

So my question is, why does the spec'ed current limit vary +/- 0.5 A? Is it mainly due to chip to chip variation, variation due to temperature, or something else? I ask because I am looking to lower the current limit below the 1 A spec., to 0.8 A or lower, and so far have not encountered any issues by simply increasing the resistor value.

Thanks.

  • 0
    TI__Genius 13760 points

    Hi,

    Welcome to E2E!

    The electrical characteristics table considers both items you mentioned, device variation, and temperature. Increasing the value of the current limiting resistor will lower the current limit setting like you're seeing in your tests, but we did not acquire data for the lower current limit settings you're testing. We would not be able to guarantee current limit setting variation for the values not listed on the datasheet.

    Best regards,

    Andy Robles

  • 0 in reply to Andy Robles
    Prodigy 40 points

    Thank you Andy for the quick reply.

    So would it be fair to say that this variation (+/- 0.5 A) is not over time i.e. lifetime of the device? Any feel on whether temperature or device variation is larger?

    Thanks!

  • 0 in reply to Srdjan Najhart
    TI__Genius 13760 points

    Hi,

    Under normal operating conditions(i.e. not excessively over stressing the device over its abs max specs), the variation will also include variation over time. For this device, and this spec I would say both temperature and device variation impact the margin of the spec equally.

    Best regards,

    Andy Robles