ADC3563: External reference for 1.6V

ttd

Mastermind 7860 points

Part Number: ADC3563
Other Parts Discussed in Thread: ADC3644, ADS8860

Dear Technical Support Team,

According to "8.3.3.2 External voltage reference (VREF)", it is required 1.6V for VREF.

Could you please provide information on the recommended circuit for the reference voltage?

For example, REF35160 is 1.6V reference voltage IC.

Is it possible to connect REF35160 and VREF of ADC3563?

REF35160 seems not to integrated ADC Drive Buffer, so external opeamp is necessary(REF35160 ⇒OPA⇒VREFof ADC3563)?

Best Regards,

ttd

7 months ago

0 ttd 7 months ago

Mastermind 7860 points

I found ADC3644 can accept REF35160(REF=1.6V) directly.

Is it same for ADC3563?

https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1291371/adc3644-external-reference

Best Regards,

ttd

0 Drew Harrell 7 months ago in reply to ttd

TI__Intellectual 2250 points

Hi ttd,

Yes, you can connect REF35160 (1.6 V) directly. However, if you plan to use this reference and connect it to multiple devices, then yes you would need to use a unity gain amplifier in between. If you cannot place it close to the DUT then you would also want that unity gain amplifier.

Best regards,

Drew

0 ttd 7 months ago in reply to Drew Harrell

Mastermind 7860 points

Hi Drew,

Thank you for your reply.

According to the block diagram of datasheet, External reference for 1.6V mode seems not to have internal buffer like 1.2V mode(it has x1.33 buffer) .

For precision ADC, ADC code has drop without reference buffer like following when 1MSPS with ADS8860.

https://www.tij.co.jp/jp/lit/an/sbaa390/sbaa390.pdf?ts=1705974692740

I am concerned that a 65MSPS high speed ADC like the ADC3563 would cause the same problem.

Question:

If I connect the output of the REF35160 (1.6 V) without buffer, does the ADC3563 have this problem?
Is there actually a built-in reference buffer for 1.6 V that is not shown in the diagram?

Best Regards,

ttd

0 Drew Harrell 7 months ago in reply to ttd

TI__Intellectual 2250 points

Hi ttd,

Unfortunately, we haven't tested settling time on this device.

If you look at the DC accuracy of the ADC35xx devices, you will see these are an order of magnitude worse vs. the ADS8860 device you pointed out.

The best solution would be to use the EVM to measure this based on your application.

Regards,

Drew

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ADC3563: External reference for 1.6V