ADS8866: Low Power

Hello Steve,

We do not have data under these specific conditions. Would it be an option to keep VREF=2.5V when DVDD/AVDD are still at 3.3V to meet the conditions for 50nA ?

Also, with AVDD=DVDD=3.3V and Vref=0V, you will need to make sure that the input pin AINP is between +/-0.3V, or you will exceed the ABS max spec of -0.3V<AINP<VREF+0.3V, which could damage the device.

If you can confirm that the input will be 0V when Vref=0V, then I can test a device in the lab to see if there are any leakage paths that would increase the current beyond the data sheet spec of 50nA.

Regards,
Keith N.
Precision ADC Applications

Hi Keith....
Yes the Vref powers the source as well as the reference pin to the a/d so AINP should be gnd....

Thanks
Steve

Keith....
Please keep me posted on your low power test...

Thanks
Steve

Hi Steve,

I will provide an update to you (hopefully with some conclusive data) no later than Friday, 2/15/2019.

Regards,
Keith

Hi Steve,

I was able to modify an EVM board and take some measurement data. In all cases, I could not see an increase in current on AVDD when removing the Vref input. I did this with the Vref pin floating and with the Vref pin tied to ground.

There was some noise when trying to measure this current, but the initial results look promising. Please note that this is not a specification that TI can guarantee under these conditions.

Regards,
Keith

Thanks Keith.....
That does sound promising....

Steve

Keith....
If I may one more question with respect to this part....The temp spec says max 85C....This is junction temperature, correct? Meaning if I want to operate this in an environment of 125C for periods of time but can guarantee that I can keep junction at 85C I should be able to do so?

Thanks
Steve

Hi Steve,

Since the power dissipation is very low in this device, the ambient temperature and the junction temperature are almost equal, so we just specify ambient ratings.

In most cases, the ambient will be the actual case temperature of the part on the board, which can be quite different from the ambient air temperature around the entire system.

We cannot recommend going beyond 85C, but if the part and PCB are inside an enclosure and the external ambient air temp swings above 85C for a short period of time, then it is possible the temperature of the part will not see the extremes, but more of an average. As long as the maximum case temperature of the part does not exceed 85C, then you will be within the recommended operating temperature.

Regards,
Keith