TL431A-Q1: Comparator response time

AshKhu

Part Number: TL431A-Q1

Hello. I had a question about the TL431 when being used as a comparator.

We are using this part as a comparator with a threshold of 2.5V. The circuit works but it seems like the response time is slightly different depending on the voltage at the reference pin (VREF). For example, the time it takes for the part to conduct is slower at 2.5V VREF than when 4.5V is applied at VREF. Is there an equation that characterizes this? We assumed that the turn on time for the comparator circuit would be negliable but it seems like its significant for our application (we are seeing 4-5 us of delay).

Thank You.

over 6 years ago

0 Marcoo Z over 6 years ago

TI__Mastermind 19370 points

Hi Ashiful,

We do not have an equation that characterizes this delay. Part of it has to do with how much current is going into the VRef, because at higher voltages the VREF will consume more current and this will cause the change to happen faster. I would also recommend adding a current limiting resistor on the VREF pin.

-MZ

0 AshKhu over 6 years ago in reply to Marcoo Z

Prodigy 20 points

Hi MZ,

We have a current limiting resistor on VREF. Is there any capacitance on the VREF pin we should take into account?

0 Marcoo Z over 6 years ago in reply to AshKhu

TI__Mastermind 19370 points

Hi Ashiful,

I was on travel so I didn't get to this. There is no capacitance on the VREF pin you need to take into account.

-MZ

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TL431A-Q1: Comparator response time