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# TPS3890: Explain TPD(f)

Part Number: TPS3890

Hi,staff

TPS3890 Explain TPD(f)

Datasheet (SLVSD65A) page11 describes the description of "SENSE(rising) to /RESET propagation delay" (TPD(r)).
This makes it possible to understand the time adjustment that /RESET deasserts.

However, there is no description of "SENSE(falling) to /RESET propagation delay" (TPD(f)) in the datasheet.
The mechanism (method) by which /RESET is asserted by this is unknown.

Is it possible to provide materials that explain TPD(f)?

※There is no CT in the application note (SBVA047)
There is a description of /RESET assert.
There is no explanation of /RESET assert with CT.

best regards
cafain

• Cafain,

Please see the timing diagram as I have attached below. tPD(f) is similar to tPD(r) but instead when the SENSE enters a UV condition and asserts a falling edge.

Thanks,
Abhinav.

Hi, Abhinav san

The question is the operation of tPD(f) when connecting a capacitor to adjust Delay to CT terminal.

Looking at the timing diagram in Figure1, tPD(r) and tPD(f) are delayed at the same time.

Calculate the delay value of tPD(r) by Equation1 page11 of the datasheet,
Is this calculated Delay value valid for tPD(f)?

tPD(r) = tPD(f)

For example, if tPD(r) is 100usec in Equation1, will tPD(f) also be 100usec?

※ I understand that when the CT terminal is set to Open,
the delay time is different between rising and falling with tPD(r)=18us(typ) and tPD(f)=25usec.

best regards
cafain

cafain,

My first instinct is that Equation 1 on page 11 similarly applies to tPD(f), the only difference being a change in tPD(r)(nom) to tPD(f)(nom). This would change the value slightly but would still reflect the value from equation 1. This being said, I need to look into this to be 100% sure. I will do some calculations and see if we have any tests that match up.

Thanks,

Abhinav.

HI, Abhinav-san

best regards
cafain

Cafain,