TL431: About the rise time.

Kengo,

Is ch2 connected to a load? Do you have any load capacitance?

As section 10.2.2.2.4 states in the datasheet, the expected start-up response behavior for TL43xx is a fast response up to ~2V then slowly charges to its programmed value due to the compensation capacitance required for stability criteria. As shown by the application curve, this is only a few microseconds however. Does your application require a specific response time?

Hi Michael,

Thank you for your response.

There is no load capacitance with only load resistance( 1kohm).

I think that it is considerably too longer than the response time of the data sheet.

Why is the response time longer?

If you have VCC=24V or close rise time data, could you share it ?

Sincerely.

Kengo.

Hi Michael.

Thank you for your reply.

Does this result vary from device to device?

Is there anything that can be considered as a factor of the circuit?

Are there any devices that respond faster?

Sincerely.

Kengo.

Kengo,

Yes this timing will very slightly from device to device which is why it is not a guaranteed spec. But the main factor is board layout and configuration. The trace length, trace width, length of wire for measurement, parasitic capacitance, component tolerance can all play a factor in the measured value in addition to the voltage levels for operation. The device has built in capacitance as previously mentioned so there is not much more that can be done to speed up the timing. 

What is the requirement for your application? You may get a sharper response using Figure 34 in the datasheet with the additional transistor.