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Original question:

TPS3899: V_HYS on datasheet

TPS3899: Voltage supervision with a tolerance lower than HYS tolerance.

Alberto E.
Prodigy 181 points
Part Number: TPS3899
Other Parts Discussed in Thread: TPS3703,

Hello, I have a question regarding this device and how it works.

Reading the dataseet, I see that the RESET is asserted when the SENSE is below Vit-, and it's released when it's a 5% greater (this is the hysteresis threshold tolerance) So the release of the RESET will be when Vit- + (Vit- * 0,05), is that right?

But what about if I want monitor a voltage with a 2% tolerance, for example.

If I want monitor a 1V with 2% tolerance, the RESET will assert at 0,98V but it won't release until 0,98+(0,98*0,05)=1,029V, that is higher than the nominal voltage, for example, so It might happen that RESET never release if the input voltage does not pass the nominal voltage by 2-3% aprox. In this case, I guess I should choose a supervisor with a lower hysteresis tolerance, right? maybe 1% to monitor voltages with a low tolerance, right?

Thanks!!

  • +1
    TI__Mastermind 19370 points

    Your calculations on the TPS3899 are correct. 2% tolerance on a voltage rail is very tight. Most 1V supplies probably already have a 2% error built in so it seems like tolerance should be expanded. Most of our supervisor devices do have hysteresis of at least 1-2% so this will be a problem for your requirement. In addition each threshold has its own accuracy of 1.5-2%. Our best accuracy supervisor is the TPS3703, please evaluate that device to see if it can meet your needs. 

  • 0 in reply to Marcoo Z
    Prodigy 181 points

    Ok, thank you so much! I'll check that device Wink