ADS8695: LPF bandwidth question

Tess Chen

Part Number: ADS8695

Hi Team,

There is a description show for LPF in the datasheet. The -3dB cut off frequency is 15Khz. As this device speed could be reach to 500Ksps, for signal above 15Khz, does it will be affected by the LPF? For example, customer's signal input will up to 20Khz. In this case, this device would suit their design or not? Thanks.

over 1 year ago

0 Ryan Andrews over 1 year ago

TI__Guru 61226 points

Hello Tess,

The low-pass filter in the ADS8695 has a fixed -3-dB cutoff frequency (15 kHz) that is independent of the gain setting and sampling rate. If a customer requires more signal bandwidth up to 20 kHz, they should consider an alternate device.

What is the input range that the customer requires for this application?

Regards,

Ryan

0 Tess Chen over 1 year ago in reply to Ryan Andrews

TI__Intellectual 2675 points

Hi Ryan,

The maximum input is about 20Khz. Need sample rate >100Ksps, single channel, 18 bit above. SPI interface and +/-2.5V common mode input range. Do you have better solution?

0 Ryan Andrews over 1 year ago in reply to Tess Chen

TI__Guru 61226 points

Hi Tess - let me look into some other products.

Can you confirm if the wide input voltage range is required? Do they care about input impedance? The integrated analog front-end is responsible for the limited signal bandwidth. However, it provides the benefit of supporting a wider input range and higher input impedance.

Regards,

Ryan

0 Tess Chen over 1 year ago in reply to Ryan Andrews

TI__Intellectual 2675 points

Hi Ryan,

They still plan to use ADS8695 for lower BW signal input. 20Khz application, better to have high input impedance. If no PGA on board, they have to add a op amps in the chain.

0 Tess Chen over 1 year ago in reply to Tess Chen

TI__Intellectual 2675 points

Hi Ryan,

Any update for the device recommendation?

+1 Ryan Andrews over 1 year ago in reply to Tess Chen

TI__Guru 61226 points

Hi Tess - how many channels are required for this application? We have an 8-channel device in preview now which includes a similar integrated AFE with selectable low-pass filter bandwidth (21 kHz and 400 kHz). This device has two ADC cores, each with a 4:1 MUX in front, giving you 2 MSPS / CH.

https://www.ti.com/product/ADS9817

Regards,

Ryan

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ADS8695: LPF bandwidth question