ADC08DJ3200EVM: Use of differential input

Emir Karamehmedovic

Part Number: ADC08DJ3200EVM

Dear TI,

it seems that the EVM board ADC08DJ3200EVM has connected only the single-ended input to the ADC. Differential inputs INA+ and INA- are disconnected by jumpers R1/R179 and R4 at the balun1 output. In the manual it doesn't say anywhere that this is the case, it is even recommended to use the differential input INA+/- as the ADC is optimized for that. Do I need to remove the two jumpers close to the balun output and mount them to pass the differential inputs? This is really inconvenient...

over 2 years ago

0 Neeraj Gill over 2 years ago

TI__Mastermind 20541 points

Hi,

By default ADC EVM is setup to use onboard balun which takes single ended signal and convert it to differential signal for the ADC input.

if you want to bypass the onboard balun and use external balun you can do the following.

You will need to DNI R1, R4 and populate R180 and R179 with 0.1 uF caps for channel A.

You will need to DNI R6, R9 and populate R151 and R162 with 0.1 uF caps for channel B.

Regards,

Neeraj

0 Emir Karamehmedovic over 2 years ago in reply to Neeraj Gill

Prodigy 100 points

Hi Neeraj,

I have outputs from a fully differential amplifier matched for 50Ohm inputs that I want to sample with the ADC. I do not have another balun. So you suggest to remove the R1 and R4 and mount capacitors (make AC coupling) in place of R179 and R180.

0 Neeraj Gill over 2 years ago in reply to Emir Karamehmedovic

TI__Mastermind 20541 points

Hi Emir,

Yes if you want to AC couple the amplifier with ADC you need to remove R1 and R4 and install the AC coupling caps. If you need to DC couple first make sure you meet the common mode requirement of the ADC(0 volts) and then replace R179 and R180 with zero ohms.

Regards,

Neeraj

0 Emir Karamehmedovic over 2 years ago in reply to Neeraj Gill

Prodigy 100 points

Thanks Neeraj,

I think I can meet the Vcm requirements, but still AC coupling may be more secure way to go. Thanks!

Data converters

Data converters forum

ADC08DJ3200EVM: Use of differential input