TPS3808: Power On Reset Function

Hi,

I’m leaning towards using three of the TPS3808 devices because I need to have a power on delay that can be retriggered to power cycle a processor module.   The only disadvantage with the TPS3808 is that the 15ms delay needs capacitor Ct = 2.5nF and it could be expensive to find an accurate 2.5nF capacitor.   For the moment I’ve calculated that using Ct=2.7pf +/- 0.25pF is closest we have and produces delays between 15.8ms and 16.1ms. This should work because it guarantees a power on delay greater than 15ms delay.  I’m trying to find out if the IC’s fixed 20ms delay is acceptable and if so I could use the recommended pull up on  the Ct pin instead.

For reference, The power on reset function that I need has to produce an output that is initially low until a control is negated, then a programmable amount of time later the output goes high permanently (not pulsed).

Any comments or thoughts would be appreciated.

Thank you.