TLV3491: Start-up time?

Hi Archie,

When looking at comparable parts, I would estimate the start-up delay to be no worse than 1ms.

I really appreciate your question and I would like to know why you are concerned about this delay for a nanopower device. Most of the time we see these devices being left on.

If you need a faster comparator I would recommend the TLV7011 which is 10x faster.

Best Regards,

Joe

Applications Engineer

Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

Archie

Thanks for your patience on this one.  I really wish I could provide the answer you want.  Unfortunately, since the TLV3491 does not have an integrated power on reset circuit like the TLV703x/4x family, it's actual output state is undefined during the startup time.  One question regarding your application.  Do you know the ramp rate of your supply when you are powering up your circuit.  If it is slow, it is fair to assume that the comparator output will be high Z when the supply is less than 1V because there is not enough voltage to turn any internal pulldown transistors on.  But when the supply starts to approach the min recommended operating voltage, the output very well could go low momentarily.  The only way to find out would be to get some samples and run the following test.

Ramp the supply slowly from 0 to say 3.3V or 5V while using a different supply to maintain a fixed voltage of 0.1V on the noninverting input and 0V on the inverting input.  I would also put a weak pullup resistor (say 1M) on the output connected to V+.  As the supply ramps up from 0V, the output will track the supply due to the weak pullup resistor.  But at some point, you may notice the comparator output go low momentarily before the supply reaches a voltage close to the min operating voltage.  But if the comparator stays high until the min operating voltage is reached, then we can assume that typical devices are high Z until the comparator starts to function.  Sorry this is a bit more than you are probably looking for but this is what we would need to do to determine what is happening during startup.  

Chuck.