PGA 280 + ADS1259

Hello Rahul,

When performing the board layout, the main goal is to try to isolate the analog path signals from noise sources.  Whenever possible,  avoid crossing the analog signal path with the digital signal path and keep them isolated.  The analog signal path should be isolated from noise sources such as switching supplies, avoid heat sources close to the analog I/O , route differential traces together, etc. Keep the traces between the PGA280 output sand the ADS1259 inputs short. In general, when starting the layout, start by routing the analog signals since these are the most sensitive.  The bypass supply capacitors should be in close proximity to the supply pins. Differential low-pass capacitors close to the inputs of the ADS1259 and PGA280 inputs. 

Please find attached the ADS1259+PGA280 EVM gerber files:

7002.6512211_ADS1259_PWB_A.zip

3632.ads1259_reva_layout.pdf

In terms of layout consideration, attached is some additional presentation I found regarding analog layout recommendations that talks in detail about differential signals, bypass capacitors and grounding layout considerations.  

 Presentation with layout recommendations:

 3005.analog_Layout -recommendations.pdf

For convenience, also find below a link to  the generic Design notes regarding  layout/grounding:

http://e2e.ti.com/support/data_converters/precision_data_converters/w/design_notes/general-pcb-layout-questions.aspx

In addition, figure 65, p41 on the ADS1259 datasheet provides some recommendations specific to the PGA280 driving the ADS1259.  The schematic shows a 1uF capacitor across VREFP and VREFN; (the ADS1259EVMuses a 10uF capacitor) and 1uF to 10uF capacitor on the BYPASS pin.  A differential low pass filter with 47Ohm resistors and a COG grade 10nF capacitors is used in close proximity to the input pins of the ADS1259; low-pass common-mode COG capacitors of  47pF at the inputs are also shown on the ADS1259EVM.  Depending on the signal you are measuring;  you may also consider low-pass filters at the inputs of the PGA280.

 Thank you,

Best Regards,

Luis