ADS7953: Timing sequence

Hello,

The analog supply, VA always needs to be at the same level or higher than the digital supply, VBD.The analog supply should be power on before or at the same time as the reference as well.

When powering up the device, it could act abnormally if the digital supply ramped up before the analog supply.  The digital input to the ADC should also not be High before the ADC is powered up. It is best to fully power up the device first, and then try to communicate with it.

Regards

Cynthia

Hello Cynthia,

Thank you for your support.

If the analog power supply (VA)and the digital power supply (VBD) are powered on at the same time, they are powered by the same power supply(3.3V),will it affect the the ADC working normally when power on?

How long does reference should be delayed to the analog supply when power on? 20ms, 100ms ,500ms...Is there any delay time limited?

Thank you.

Kevin

No problem,

In general, both power supplies coming up at the same time is usually fine. But I would suggest to confirm that each rail is ramping up together, especially if VA and VBD are at different voltage levels. If VBD is lower, the rail might ramp up faster than VA, which could be causing the issue.

There doesn't seem to need a specific delay time between REF and VA. This should not cause an error, as long as each supply is settled before conversions are taken place.

Regards

Cynthia

Hello Cynthia,

Thank you for your support.

In my design, the ref2.5V is powered by 3.3V,the VA connected with VBD on same power supply 3.3V.

The 2.5 is lower than 3.3V, I test the rise time when power on.The ref2.5V is less than 0.5ms powered before 3.3V when power on.Does it will effect normal work?

Thank you.

Kevin