This reference design provides accurate measurements of AC voltage and current inputs using a precision 16-bit SAR ADC over a wide input range, covering protection and measurement range (including sampling requirements of IEC 61850-9-2), simplifying system design and improving trip time performance and reliability. The analog input module (AIM) is isolated from the host processor using a digital isolator with an integrated power. For a limited function and cost optimized design approach, An AC AIM can be designed using only three TI products, reducing system cost and board size. The alarm feature identifies the AC analog input faults on a sample basis for faster fault detection. The ADC has an additional auxiliary channel to diagnose the supply output of the digital isolator. A 12-bit ADS8668 ADC with a gain amplifier can increase the dynamic range by using programmable internal ranges, further optimizing the system cost.
- This reference design is based on ADS8688A 16-bit SAR ADC and supports measurement of up to 16 analog inputs by daisy chaining
- ADC interface isolated from host for improved safety in harsh operating conditions using ISOW7841 with integrated power converter providing current output of > 60 mA with efficiency ≥ 45%
- AC AIM provides ENOB of > 14.9 bits, SNR of > 91 dB, and THD of > –110 dB
- 12-bit ADC8668 with front-end gain amplifier for increasing dynamic range of low-voltage output sensors in cost-optimized applications
- Load switch used at input of ISOW7841 to protect AC AIM during output overload