Hi team,
My customer is using TL7733B and seeing the reset delay time during the 1st power-on is much longer than the calculated delay time. Below their circuitry and the measured waveform. The programmed delay time is 120msec and they get consistent delay of ~ 123msec when it is powered up, and toggle by the sense pin. But the initial power up is ~ 390msec.
In datasheet, it mentioned that the timing capacitor is discharged to about 0.6V, not completely to 0 volt. So they do not expect the startup delay time to increase by 3 times.
In figure 2 in the datasheet, it also did not shows there is any startup delay time once the Vin is above the threshold or sensed voltage. Is there any data on the initial power up delay time needed for the device? Vref ramp time? etc....
The input 12V from their system rise very quickly to above the threshold voltage as shown in the yellow waveform. it seems that from their captured waveform, the the RESET is out of the "undefined" state within 100msec of the Vin rising.
The customer would like to know:
- Can we expect that the timing for the initial turn-on reset toggle of ~390ms to be consistent?
- Does the time delay equation provided by the datasheet make the assumption that the timing capacitor is already charged for 0.6V?
- Can we get an equation to reliably calculate what we can expect to see for the turn-on reset toggle?
Regards,
SK Loo
