Please let me know about UVLO response time for instantaneous power failure.
I want to know the condition of power failure and momentary recovery.
When the time for power failure to recovery is too fast, I guess that UVLO can't detect this failure.
Is there spec for require failure time?
Best regards,
Satoshi
Hi Satoshi,
If you are using EN/UVLO pin to set UVLO Voltage and there is a power failure, the device starts to turn OFF within td,off as shown in the timing diagram below.
As you can see in the table below, the Turn OFF delay is around 11us. The Actual Fall time, tf is dependent on the Load and Output Capacitance.
Can your Power fail and Come back within 11us ?
Praveen-san
Thank you for advice,
I want to know below response time at the time of "???".
I think that when come back is too fast (glitch), internal circuit of UVLO function is not operate.
Please let me know about the border of UVLO operate or through.
Best regards,
Satoshi
Hi Satoshi,
Please ignore my previous reply as I have considered the device to be TPS2595 and not TPS25925.
Now, for TPS25925 there is an de-glitch delay for the EN/UVLO signal falling edge.This delay is intentionally kept low (1 µs typical) for quick detection of power failure. For applications where a higher de-glitch delay on EN/UVLO is desired, or when the supply is particularly noisy, it is recommended to use an external bypass capacitor from EN/UVLO to GND. The same is explained in section 8.3.4 of datasheet.
After the 1us de-glitch time, the internal Mosfet gate is pulled low within 0.4 us (Typical). So, The total time time taken from the EN/UVLO below its threshold to Gate being pulled Low is 1.4us (typical).
As mentioned before the actual slew rate of Vout fall is dependent on Cout and Load. To avoid turn-off due to glitches, you can use a Decoupling cap at EN/UVLO to GND.
Hope this answered your question.
