ADS1120IPWR Output Drift: Common Reasons and How to Fix Them

ADS1120IPWR Output Drift: Common Reasons and How to Fix Them

When using the ADS1120IPWR analog-to-digital converter (ADC), you may notice that the output signal starts drifting over time, which can lead to inaccurate measurements. This drift can be caused by various factors, but don't worry! We’ll break down the common reasons for output drift and provide step-by-step solutions to resolve the issue.

1. Power Supply Instability

Cause: One of the most common reasons for output drift is an unstable or noisy power supply. The ADS1120IPWR requires a clean and stable power source to maintain accurate performance. If the power supply fluctuates or has noise, it can affect the ADC’s conversion process, leading to drift in the output.

How to Fix It:

Check your power source: Ensure that your power supply is stable and within the specified voltage range (2.0V to 5.5V for the ADS1120IPWR). Use a Low Dropout Regulator (LDO): If your power supply is noisy, use an LDO to provide a cleaner voltage. Add decoupling capacitor s: Place capacitors (typically 0.1 µF and 10 µF) close to the power pins of the ADS1120IPWR to filter out noise and reduce voltage fluctuations.

2. Temperature Variations

Cause: The ADS1120IPWR, like most electronics, is sensitive to temperature. Temperature changes can cause shifts in the internal reference voltage or affect the internal circuitry, leading to output drift.

How to Fix It:

Monitor the temperature: Use a temperature sensor to monitor the temperature in the area where the ADC is located. Implement temperature compensation: If your application is sensitive to temperature, consider adding temperature compensation in your firmware or hardware. Use an external precision reference: If temperature stability is critical, consider using an external voltage reference with a low temperature coefficient.

3. Improper PCB Layout

Cause: The physical layout of your printed circuit board (PCB) can contribute to output drift. If the ADS1120IPWR is exposed to noise from nearby components or if the grounding is inadequate, this can lead to fluctuations in the ADC’s readings.

How to Fix It:

Ensure good grounding: Connect all ground points to a single ground plane, and avoid long ground traces. Route sensitive signals carefully: Keep the analog input and reference pins away from noisy digital traces or high-power components. Use shielded traces: For critical analog signals, use shielded traces to minimize the effect of external interference.

4. Reference Voltage Issues

Cause: The ADS1120IPWR relies on an accurate reference voltage to convert the analog input signal into a digital output. Any instability in the reference voltage can lead to output drift.

How to Fix It:

Check the reference voltage: Ensure that the reference voltage is stable and within the expected range. The ADS1120IPWR’s reference voltage is typically supplied internally, but if you're using an external reference, it must be clean and precise. Use a low-noise reference source: If you're using an external reference, make sure it is low-noise and stable, such as a precision voltage reference IC. Apply a reference buffer: Use a buffer (e.g., an op-amp) between the reference source and the ADC to ensure a stable reference voltage.

5. Input Impedance Mismatch

Cause: If the input signal to the ADS1120IPWR has a high source impedance, this can affect the accuracy of the ADC readings and cause drift, especially when the ADC’s internal sample-and-hold capacitor is charged.

How to Fix It:

Reduce input impedance: Make sure that the impedance of the signal source is low (below 10 kΩ). If necessary, use a buffer or operational amplifier with low output impedance to drive the ADC’s input. Use proper filtering: Implement a low-pass filter at the input to avoid high-frequency noise, which can affect the stability of the ADC’s sampling process.

6. Internal Filter Settings

Cause: The ADS1120IPWR has internal digital filters that can affect the output response. If the filter settings are incorrectly configured, this could lead to output drift or unexpected behavior.

How to Fix It:

Review the filter settings: Ensure that the internal filters are set appropriately for your application. If you're dealing with fast-changing signals, consider using a lower filter cutoff to avoid excessive smoothing. Configure the filters properly: You can adjust the filter settings using the device’s configuration registers. Make sure the filter settings match the expected signal frequency and behavior.

Conclusion: Troubleshooting ADS1120IPWR Output Drift

In summary, if you experience output drift with your ADS1120IPWR, the issue is likely due to one or more of the following factors: power supply instability, temperature variations, poor PCB layout, reference voltage issues, input impedance mismatch, or incorrect filter settings. By following the solutions outlined above, you should be able to pinpoint the cause of the drift and take the appropriate steps to resolve the issue, ensuring accurate and stable ADC readings.

If you’ve addressed all of these potential issues and the drift persists, it may be worth verifying the integrity of the ADS1120IPWR chip itself or considering replacement if it's malfunctioning due to hardware damage.