ADS7828: How to measure negative voltage by using ADS7828?

Hello,

There are a couple ways to do this, but I suggest doing your own research to see which option is best for your use case. There are power converters that can do this, or shifting the voltage up can also work. 

But again, this is something that depends on your application

Regards

Cynthia

Thanks for your reply, Cynthia.

Let me describe my application in detail.

I intend to use onboard ADS7828 to monitor an IC’s integrated LDO output, which is -1V. And I am going to design a simple op-amp inverter circuit, because of its high input impedance, to turn the -1V to 1V then let it go to ADS7828. On E2E, I saw someone asked a similar question regarding “Negative and Positive Voltage Measurement with ADC.” The ADC mentioned in the question was ADC78H90 and the replier had provided a recommended circuit, which adopted LMP2021. That is why I just asked the above question for the recommended circuit specific to ADS7828.

In my case, the first thing that comes into my mind is: the slew rate of the op-amp should meet the ADC’s sampling rate. So, do you have any recommended op-amp both for my application and ADS7828? In addition, can you let me know how to choose a suitable op-amp for ADS7828?
Your kindly help will be appreciated.

Regards,
Lin, S.P.

All the inputs seem to be DC inputs, thus slew rate should not be an issue. 

This device is a max 50kHz sampling rate, which is actually slow compared to the performances available from op amps, thus, the options are quite vast. I think it would be best to ask the op amp team for guidance on this. I have let them to know and they will respond to this post. 

I will mention that there are a collection of circuits for common applications for both Op amp and ADC. 

Regards

Cynthia

Hey Lin, 

Please check out Ron's FAQ of voltage scaling: https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/942778/faq-voltage-scaling-for-almost-any-application-single-ended

All the best,
Carolina