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TPS7B4250-Q1: Output capacitor requirements

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Replies: 4

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Part Number: TPS7B4250-Q1

Hello Team,

following question raise up:

We could not understand the sentence highlighted below. Does it mean the min out cap -> 1uF +/- 30%?

BR Josef

  • Hi Josef,

    For this device, the worst-case tolerance of 30% means the minimum capacitance is 0.7uF; this minimum capacitance needs to be maintained at all time when using the LDO. Capacitor and capacitance are different things. Here we have a 4 minutes video that explains the capacitor's capacitance degrading at different conditions.
    training.ti.com/ldo-basics-capacitor-vs-capacitance

    Regards,
    Jason Song

  • In reply to Jason Song:

    Hello Jason,

    that's clear regarding capacitor tolerance. But why is not 0.7uF used in our specification for minimum capacitance? We could also use a for example 0.8uF with +/- 10% and then it's in the range. I think it's a little bit confusing between min/max spec in datasheet and mention a capacitor tolerance.

    Many Thanks for clarification
    Josef

  • In reply to Josef Warta:

    Hi Josef, 

    I agree with your point. We have datasheet both using capacitance and capacitor in this table. For 0.8uF with +/-10%, you do need to look at the capacitor's datasheet to know when over different temperatures if that +/-10% is still true. For most of the customers, sometimes, it's easier to guide them with what size of capacitor they can use as some customer does not pay enough attention to capacitor vs capacitance. However providing the capacitance requirement does allow more flexibility for customer to pick capacitors, but they will need to cautious on the variation of capacitance change over voltage and temperatures. 

    Regards, 
    Jason Song

  • In reply to Jason Song:

    Hello Jason, thanks for clarification. Now I understand your motivation 'capacitance vs. capacitor'. Best Regards Josef

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