ADS1119: ±1V DC Measurement with ADS1119

alikaan

Part Number: ADS1119
Other Parts Discussed in Thread: ADS112C04, ADS8689, ADS125H02

Tool/software:

Hi, is it possible the measure ±1V DC with ADS1119 ? If so how can I connect the adc input ? Is there any app note for that application ?

10 months ago

0 Angel Rodriguez de San Miguel Bermudez 10 months ago

TI__Expert 8130 points

Hi Alikaan,

The ADS1119 cannot measure negative voltages with respect to GND.

It can however measure negative differential signals, where the voltage at AINN is higher than the voltage at AINP, and the ADC outputs a negative binary code (in binary two's compliment).

The absolute voltages at the input pins with respect to GND must still be positive, however.

This is explained in detail in the following FAQ post: (+) [FAQ] Can my ADC measure negative voltages? - Data converters forum - Data converters - TI E2E support forums.

A potential solution would be to Bias one of the input pins and level-shift your input signal for your ±1V measurement.

For example, if AINN = 1.5V, and voltage applied to AINP = 0.5V to 2.5V (±1V signal level shifted), the ADC would measure ±1V differentially.

Best Regards,

Angel

0 Angel Rodriguez de San Miguel Bermudez 10 months ago

TI__Expert 8130 points

Hi Alikaan,

Another option is to upgrade to the ADS112C04, which is a pin-to-pin compatible device that offers bipolar supply capability.

With Bipolar supplies, you would be able to read negative voltages (±1V DC) directly without having to bias/level-shift your input signal.

Best Regards,

Angel

0 alikaan 10 months ago in reply to Angel Rodriguez de San Miguel Bermudez

Expert 2315 points

Hi, any solution for -5VDC to +5VDC ?

0 Joachim Wuerker 10 months ago in reply to alikaan

TI__Mastermind 23275 points

Hi Alikaan,

you could simply add a resistor divider between your input signal and GND and then measure the signal across the bottom resistor with ADS1119 when using a bipolar power supply for the ADC. If you use the internal voltage reference of ADS1119 and PGA gain = 1, you just need to make sure the voltage across the bottom resistor stays within +/-2.048V.

We also have quite a few ADC options that natively support a +/-5V measurement range, however all those ADCs have a SPI interface. Would SPI instead of I2C be acceptable?

Regards,
Joachim Wuerker

0 alikaan 10 months ago in reply to Joachim Wuerker

Expert 2315 points

Hi,

SPI OK for us. Please let me know the part numbers.

0 Joachim Wuerker 10 months ago in reply to alikaan

TI__Mastermind 23275 points

Hi Alikaan,

in that case you could look at the following options for example:
- ADS8689 (only requires a unipolar 5V power supply. Input impedance of 1MOhm)
- ADS125H02 (requires a bipolar e.g. +/-15V power supply. Input impedance of ~1GOhm)

We have other SPI options as well depending on your resolution, channel count, and data rate requirements. Feel free to look through our parametric search:
https://www.ti.com/data-converters/adc-circuit/precision-adcs/products.html#3093max=12%3B12.288%3B12.5%3B15.5%3B10%3B10.24&sort=1130;asc&

Regards,
Joachim Wuerker