REF3440: ADS8885 ref voltage

Alen Barisic

Intellectual 1300 points

Part Number: REF3440
Other Parts Discussed in Thread: ADS8885, , OPA333, REF5045

Hi,

could you please review our ref voltage circuit for ADS8885?

Thanks!

Best regards,

Alen

over 3 years ago

0 Marcoo Z over 3 years ago

TI__Mastermind 19370 points

Hi Alen,

I can help you with the REF3440 section.

The REF3440 requires an output capacitor on OUT_F to Gnd that is 1uF to 10uF.

Is there a reason you need the 20kOhm resistor going to OUT_F? that will give an offset error.

0 Alen Barisic over 3 years ago in reply to Marcoo Z

TI__Intellectual 1300 points

Hi Marco,

the design is based on the following

AS the RED3440 has a feedback, the idea was to save the OPA333.

The temperature drift of all devices (resistors, OpAmp, REF + ADC) should be under 10ppm/°C.

Could you please share your thoughts on this approach?

Thanks!

Best regards

Alen

0 Marcoo Z over 3 years ago in reply to Alen Barisic

TI__Mastermind 19370 points

HI Alen,

I see it forms an RC filter. That is fair.

I have not tried this approach on the bench and my bench capabilities are limited. I would still add the 1uF directly on the Out_F output due to stability.

The REF5045 also requires this capacitor. It is not shown in that figure but it does appear in the schematic.

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REF3440: ADS8885 ref voltage