ADS7835: PIN1 VREF capacitor

Haiwen Huang

Part Number: ADS7835

Tool/software:

Dears:

DS mention that VREF pin need connect a 2.2µF tantalum capacitor , Could you please help check why it has such requirement ? if customer use 2.2uF ceramic capacitor , any risk here ? Thanks.

10 months ago

0 Ben Bethel 10 months ago

Prodigy 10 points

For ADS7835, tying a 0.1µF ceramic capacitor to VREF at pin 1 is typical for stability, especially when using internal reference. External VREF needs careful layout to avoid noise coupling. If you're sourcing precision capacitors or compatible analog components, Jotrin has a great selection of ADC-related parts that can simplify prototyping and ensure compatibility with TI's data converters.

0 Tom Hendrick 10 months ago in reply to Ben Bethel

TI__Guru**** 182601 points

Hi Ben,

No worries - welcome to our e2e forum! Short answer is that yes, you can use a ceramic cap. Longer answer would involve you reading up on the differences between the two which you can do here: https://www.kyocera-avx.com/docs/techinfo/CeramicCapacitors/mlc-tant.pdf Since the 2.2uF is on the reference, using a good quality cap (X7R type) will help to maintain stability which is important for overall conversion accuracy.

0 Haiwen Huang 9 months ago in reply to Tom Hendrick

TI__Intellectual 2460 points

Tom:

based on datasheet, 2.2uF is recommend to use tantalum cap which ESR is more larger than ceramic cap, I think that can cause stability issue. Please help confirm it .Thanks.

0 Tom Hendrick 9 months ago in reply to Haiwen Huang

TI__Guru**** 182601 points

You can add a series resistor to compensate for the ESR of the tantalum cap.

0 Haiwen Huang 9 months ago in reply to Tom Hendrick

TI__Intellectual 2460 points

Tom:

As datasheet don't mention when use internal reference need to add extra resistor to keep system stable. Please help confirm this .Thanks.

0 Tom Hendrick 9 months ago in reply to Haiwen Huang

TI__Guru**** 182601 points

Haiwen,

Ceramic capacitors were not as common as they are today when the ADS7835 was released (25 years ago). I suggest that you find a capacitor footprint option that could accomodate either a ceramic or tantalum capacitor and try it out.

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ADS7835: PIN1 VREF capacitor