ADS8681: ADC Device Recommendation

Songzhen Guo

Part Number: ADS8681
Other Parts Discussed in Thread: ADS8860, ADS8920B

Hi expert,

Customer want to use ADC in hydrogen commercial vehicle. Could you recommend a suit device for us? Here are the requirements:

Input Voltage: -5 V~+5 V

Channel: 1/2(1 is better)

Resolution: >14bit

Max input signal frequency: 20kHz

Output Interface: SPI

REF: 4.096V(Better for internal)

Operation Temperature: -40~125C

Supply voltage: 5V

I find ADS8681 is almost suit those requirements. But it has a 2nd order LPF inside, –3-dB cutoff frequency for the filter is typically 15 kHz. The max input signal frequency is 20kHz. Can we turn it off?

Best Regards

Songzhen Guo

over 3 years ago

0 Dale Li over 3 years ago

TI__Mastermind 35520 points

Hi Songzhen,

The internal filter on the ADS8681 can not be turned off. Since the BW of this filer is 15kHz, a 20kHz input signal will definitely be distorted and degraded. A precision ADC without internal filter will be a good solution for your customer's, for example, ADS8860 or ADS8920B. Since most precision low voltage ADCs can only accept low voltage signal, so an attenuator should be designed for +/-5V bipolar input signal before the low voltage precision ADC. The front-end attenuator design can be referred to the application notes below:

High-voltage battery monitor circuit: ±20V, 0–10kHz,18-bit fully differential

High-input impedance, true differential, analog front end (AFE) attenuator circuit for SAR ADCs

Thanks&regards,

Dale

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ADS8681: ADC Device Recommendation