ADS42JB69: How to deal with digital and analog GND

xiao weihua

Part Number: ADS42JB69

hello, Jim

there are 3 ADCs and 1 DAC on My board , How to deal with AGND and DGND?

the datasheet said

When the ADC is used on the same printed circuit board (PCB) with a digital intensive component (such as
an FPGA or ASIC), separate digital and analog ground planes must be used. Do not overlap these separate
ground planes to minimize undesired coupling.

so I plane to split the DGND and AGND as follows, this GND plane is at layer2, each ADC has it's own analog GND and connect to DGND at one point, is there any problem with this idea?

over 6 years ago

0 jim s over 6 years ago

TI__Guru* 91947 points

Two GND plane example.pptxXiao,

On the customer EVM, we use only one ground plane. I think this is a better idea as long as you can guarantee no digital return current paths are crossing into the analog signals of the ADC. If this is not the case with your design, I would try to make the GND connections as shown in the attached example for each ADC.

Regards,

Jim

0 xiao weihua over 6 years ago in reply to jim s

Intellectual 480 points

but the Thermal pad is a whole pad, so if we split the AGND and DGND in layer2, is it
reasonable？

0 jim s over 6 years ago in reply to xiao weihua

TI__Guru* 91947 points

Xiao,

If you plan on using a split plane, yes this will be OK as long as the split is very small to minimize the loss of the thermal pad.

Regards,

Jim

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ADS42JB69: How to deal with digital and analog GND