VREF in AD9695

Hi jamesjjc,

Your query is acknowledged and will be responded by the product owner soon.

Regards,
Peevee

Hi Jamesjjc,

Yes, an on-board common-mode voltage reference is included in the design and is available from the VREF pin.
Using the VREF output to set the input common mode is recommended, please follow the instructions as described in the datasheet.

The output common-mode voltage of the ADC driver is easily set with the VREF pin of the AD9695 via SPI.

Please refer to below registers writing:

WriteRegister(0x1908, 0x04);

WriteRegister(0x18A6, 0x00);

WriteRegister(0x18E6, 0x00);

WriteRegister(0x18E0, 0x02);

WriteRegister(0x18E1, 0x14);

WriteRegister(0x18E2, 0x14);

WriteRegister(0x18E3, 0x40);

WriteRegister(0x18E3, 0x5E); buffer current setting depends on final application.

Regards,

Alvin

Hi Alvin,

Thanks for your explanation. So is this exported VREF a 1.41V CM voltage? Because I see somewhere in the datasheet says that it's a 0.5V CM voltage.

Thank you.

Hi Alvin,

Thanks for your explanation. So is this exported VREF a 1.41V CM voltage? Because I see somewhere in the datasheet says that it's a 0.5V CM voltage.

Thank you.

Hi Jamesjjc,

Yes, the exported common-mode voltage to the VREF pin is around 1.4V by above SPI writing. The AD9695 input buffer offers flexible controls for the analog inputs, such as, buffer current, the input common mode voltage will slightly change based on the buffer current setting.

Regards,

Alvin

Hi Alvin,

I see. Thank you for your explanation.

Hi Alvin,

It's a late reply but could you elaborate on the function of 0x18E0 to 0x18E2? There's no any information in the datasheet so I'm wondering why do we need to set that?