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TPS3801: Datasheet not clear: "(2) The lowest supply voltage at which RESET becomes active. tr, VDD ≥ 15 ms/V."

Markus Fueglister
Prodigy 50 points
Part Number: TPS3801

In the datasheet SLV219E Oct. 2010 of TPS3801K33DCKR there is a statement on Power-up reset voltage(2) and corresponding foot note says: “(2) The lowest supply voltage at which RESET becomes active. tr, VDD ≥ 15 us/V.”

I have nobody found which can explain what the statement “tr, VDD ≥ 15 us/V” means.

1. Could you please explain that?
2. Is there a minimum supply line ramp up rate requested?
3. If yes, shouldn’t it say ≥ 15 V/us and not 15 us/V?

  • 0
    TI__Genius 12630 points

    Markus,

    1. The spec you referring to is talking about the voltage at the RESET output during power up. As you power up the device (increase VDD voltage), the output will have a little bit of voltage until the device gets powered up completely. This is normal for all supervisors, not just TI devices. Notice the timing diagram on page 4 or of any supervisor including competitor devices have a "shaded region" to describe the RESET output when VDD has not come up fully yet. This "shaded region" is described by the spec you refer to. So what does this mean? Well as you ramp up VDD (greater than or equal to 15V/us ramp rate), the output will spike to a MAX WORST CASE of 0.2V during that time. Once the minimum VDD is reached to operate the device (1.6V according to Recommended Operating Conditions Table), then the RESET will go to the correct state whether that is "low" 0V or "high" depending on what VDD reaches and what the threshold of the specific version you are using.

    2. No. No minimum supply ramp. The spec is referring to a worst case ramp rate on VDD that provides the MAX output voltage during power on. Meaning that under the worst possible ramp rate, your output will spike momentarily to 0.2V until minimum VDD is reached. This is only during power up and applies to all voltage supervisors.

    3. I believe that is typo and should read 15V/us. We will work to fix this.

    Please if you have any more questions or anything is unclear do not hesitate to ask.

    -Michael

  • 0 in reply to Michael_DeSando
    Prodigy 50 points
    Thank you, Michael. BR Markus