RE: ADS7809 - REF pin needs 2.2 uF cap - Why?

Heiko Wolfram

Other Parts Discussed in Thread: ADS7809, ADS8509

Hello Rafael,

I am using in my design 8 ADS7809 ADCs, which are all connected to one external reference voltage. All ADCs are bypassed with a tantal capacitor of 2.2uF to ground on each reference pin as stated in the data sheet.

What is actually in this situation the recommended bypassing - Bypassing all ADCs with a tantal of 2.2uF just as I did? Or something else?

Best Regards,

Heiko

over 12 years ago

0 Tom Hendrick over 12 years ago

TI__Guru**** 174841 points

Hi Heiko,

Having the local capacitor at each ADC would be the preferred method, after buffering the reference perhaps. How is your layout done, is this a star connection? How much trace length is connecting each of the ADS7809 devices? Also, if this is a new design, would you consider swapping the ADS7809 for the ADS8509 device?

0 Heiko Wolfram over 12 years ago in reply to Tom Hendrick

Prodigy 45 points

Hi Tom,

thanks for your information. This helped a lot.

Heiko

0 Tom Hendrick over 12 years ago in reply to Heiko Wolfram

TI__Guru**** 174841 points

My pleasure! Let us know if there is anything else you need.

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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RE: ADS7809 - REF pin needs 2.2 uF cap - Why?