DAC1282: Using DAC1282 with ADS1220 instead of ADS1282 — any performance concerns?

Hello,

The DAC1282 can be used with the ADS1220, but the performance of the DAC1282 is much higher than the ADS1220.

DAC1282 is a very linear (low THD) and low noise (high SNR) device that can be used to generate a high fidelity sinewave from about 0.5Hz up to 250Hz.  Since the performance of the DAC1282 is much higher than the ADS1220, the system performance will be limited by the ADS1220. 

No concerns with synchronization; the SYNC pin on the DAC1282 simply resets the output sinewave to the zero-crossing point.

The ADS1282 is a very high performance ADC with extremely low noise compared to the ADS1220.  

Comparing noise at 1000sps and PGA gain of 1:

• ADS1220:  37.5uVrms, typical linearity 6ppm
• ADS1282:  124dB, converted to voltage noise 1.1uVrms, typical linearity 0.5ppm.

ADS1220 (1k price of $3.41) has 34x higher noise and 12x higher linearity error than the ADS1282 (1k price of $44.22).  The DAC1282 was designed to have similar noise/linearity as the ADS1282, but it can be used with other ADCs.

Questions:

• Do you know what kind of SNR and THD, or noise (uVrms) and linearity (INL) is required for the system?  We may have a better fit ADC than the ADS1220, or, a lower cost DAC.
• What type of system is this for?  What are you trying to measure, and what is the purpose of the DAC?

Hello,

Thank you very much for your detailed explanation — it was extremely helpful.

I am developing an geophone dynamic test instrument with two measurement modes:

1) DC excitation mode:
The DAC generates a precise DC current to displace the geophone coil. After disconnection through an analog switch, the ADC measures the free decaying sinusoidal voltage to calculate natural frequency, damping ratio, and sensitivity.

2) Sinusoidal excitation mode:
The DAC generates a low-distortion sinewave (1 Hz – 100 Hz) to continuously excite the geophone, and the ADC measures the steady-state response for FFT-based THD analysis.

Signal conditions:
- Initial amplitude: about ±1 V
- Late decay stage: can fall below 1 mV
- Steady-state sine measurement: 0.1 V – 1 V，12Hz

Target performance :
- Frequency accuracy: ±0.5%
- Damping ratio: ±1%
- Sensitivity: ±2%
- THD measurement down to 0.01% (-80 dB)

My main concern is ADC selection.

From your explanation, it seems the ADS1220 noise may limit late-stage decay measurement and THD accuracy.

I can first use the ADS1220 to test and see if the accuracy meets the standard.

Could you please advise:

1) For this low-frequency (1–100 Hz), high dynamic-range measurement, would upgrading from ADS1220 to ADS1282 significantly improve parameter extraction accuracy?
2) Is the performance of the ADS1220 sufficient?

Thank you again for your guidance.

Hello,

Thank you very much for your detailed explanation — it was extremely helpful.

I am developing an geophone dynamic test instrument with two measurement modes:

1) DC excitation mode:
The DAC generates a precise DC current to displace the geophone coil. After disconnection through an analog switch, the ADC measures the free decaying sinusoidal voltage to calculate natural frequency, damping ratio, and sensitivity.

2) Sinusoidal excitation mode:
The DAC generates a low-distortion sinewave (1 Hz – 100 Hz) to continuously excite the geophone, and the ADC measures the steady-state response for FFT-based THD analysis.

Signal conditions:
- Initial amplitude: about ±1 V
- Late decay stage: can fall below 1 mV
- Steady-state sine measurement: 0.1 V – 1 V，12Hz

Target performance :
- Frequency accuracy: ±0.5%
- Damping ratio: ±1%
- Sensitivity: ±2%
- THD measurement down to 0.01% (-80 dB)

My main concern is ADC selection.

From your explanation, it seems the ADS1220 noise may limit late-stage decay measurement and THD accuracy.

I can first use the ADS1220 to test and see if the accuracy meets the standard.

Could you please advise:

1) For this low-frequency (1–100 Hz), high dynamic-range measurement, would upgrading from ADS1220 to ADS1282 significantly improve parameter extraction accuracy?
2) Is the performance of the ADS1220 sufficient?

Thank you again for your guidance.