Should the W5500 EXRES1 pin be connected to GND or AGND?

TCP/IP Chip W5500
1

Hello,

I’ve noticed a discrepancy between the datasheet for the W5500 and the WIZ850io board. In the WIZ850io board, the EXRES1 (pin 10) pin is conneced to GND via a 12.4k resistor. In the datasheet for the W5500 (Figure 2, page 11), the EXRES1 pin is connected to AGND via a 12.4k resistor.

My question is, should he EXRES1 resistor be connected to GND or AGND?

Links to the documents are below:

Download W5500 Datasheet
Download WIZ850io Schematic

Thank you!

Jameson

2

This question is old now, but just for completeness: the W5500 datasheet, section 1.1 Pin Descriptions, pin 10 says that it is for biasing of (internal) analog circuits, so it makes sense that it should be connected to analog ground.

In many reference schematics analog ground and digital ground are the same.

3

Tingox, I agree with you, but the example designs do not.

In the WIZ850io schematic, EXRES1 is connected to digital ground through a 12.4k resistor, even though all of the AGND pins are connected to analog ground (see image below).

image

This circuit has both digital and analog ground, but chooses to connect EXRES1 to digital ground. This seems deliberate, but it contradicts what the datasheet says (see image below).

image
image731×336 15.1 KB

Does anybody know why? What is the correct way to connect this pin?

4

There’re GND and AGND only if you place ferrite bead between them. Otherwise both are GND. I recall there were discussions if putting ferrite bead onto both supply and ground wires is feasible and/or has side effects. And the recommendation was NOT to put ferrite bead onto the GND, only onto supply rail.