I am designing the thermal outline plane of this current amplifier ic in a 4 layer board using Eagle Pro. This board will be made using ENIG process.

After spent so much time trying to understand in the datasheet

(https://www.mouser.com/datasheet/2/256/MAX9920-1514342.pdf) if the exposed pad should or should not be connected to ground I decided to ask someone here with experience on those ic's and what are the best practices in this scenarios.

If you look at page 14, the drawing says something about exposed pad soldering but below in the pin description ic talks about "contiguous ground plane" that's for me is kind of confusing of which info should I take.

What I don't want is make a low-impedance short in the circuit because of a wrong connection of the exposed pad.


1 Answer 1


Yes, you are interpreting this correctly if you thought this is electrical ground.


This is necessary to appreciate its Rjc of 7'C/W, if you follow thermal requirements of copper 2oz then net thermal resistance depends on area on both sides with lots of thermal vias. at a minimum 1sq.in./W, as I recall, if exposed to free air then design for Tj=85'C max at max ambient, like 40'C or whatever rise inside box is.

They recommend 2oz Cu both sides on 1oz inside for 4 layers and 15 sq in. https://www.maximintegrated.com/en/design/technical-documents/tutorials/4/4083.html which seems high for a 50 mV current sense but then 100 mV max.(?)

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    \$\begingroup\$ Make sure to follow requirements of sensor wires for CMRR . I would use STP cable with shield grounded at one end if remote or guarded twin traces on board. \$\endgroup\$ Commented Aug 31, 2021 at 1:38

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