Work malfunction of AD7760

Hi oue ,

I would like to clarify some details on your setup to further understand the issue.

Can you please help clarify on the coupled ground of pin 12?

What program did you try to write that caused the Vdrive to increase to 2.8V?

Are the coupled ground of supply pins connected to pin 9?

Thanks,
Janine

Hi Janine，

The coupled ground of pin 12  and pin9 all connected the ground of system，but the coupled ground of pin 12 is not connected to the pin 9. I didn‘t write program that  caused the Vdrive to increase to 2.8V.  The program can drive the EVAL-AD7760 without the above phenomenon. It appeared in my own PCB of AD7760

Ok，I'll have a try. Keep in touch. Thanks

Hi Janine, I have downloaded the program on the AD7760, but I am unable to input signals to the ADC. No matter what signal I input to the AD770, one of Vin+ or Vin- stays at 4.096V, resulting in a status bit overflow.

Hi oue ,

What is your input to the analog input pins? These pins must not be left floating.

Thanks,
Janine

I use this configuration：. These pins are not left floating.

Thanks for sharing this, oue 

Please share the following details

• Input to VINA+, VIN-,
• Voltage at VIN+, and VIN- pins
• Schematic design.

Thanks,
Janine

VinA+ is equal to ADin_P, and VinA- is equal to ADin_N. There is input: sine wave signal (100kHz,2.5Vpp) .  But Voltagr at VIN+  is always 4.096V, and Voltagr at VIN+  is always 0V, whatever I input.

It is a schema . 

A : an on-chip differential amplifier in AD7760

Hi oue ,

Could you try and remove R81 and R88 temporarily and measure VOUTA, and VIN? This is to check if the output of the on-chip differential amplifier is as expected.

What are your supplies to the ADC?

Thanks,
Janine

Hello Janine, 

I removed R81 and R88, and tried to input a signal  but VOUTA of  the on-chip differential amplifier  is not charge. 

I supplies to the ADC with LDO（LT1962）

I supplies to the ADC with LDO（LT1962）

I supplies to the ADC with LDO（LT1962）