How to strap the LAN8720A pins?

In most applications, you want to set MODE[2:0] to 111 in order to enable the *all-capabilities auto-negotation mode.*The other modes are rather special and rarely used (such as repeated mode). In effect, this means:

In applications where you don’t have an external 1.2V regulator, you need to strap REGOFF=0, i.e.:

The last strap you need to think about is nINTSEL/REFCLKO. You need to evaluate whether you need the REFCLKO pin to output a 50MHz reference signal in your application. This is only the case if you feed the REFCLKO output to a clock input of another IC.


For the LAN8720A, you often don’t need explicit straps - the only pin where you have to seriously think for 95% of all PCB designs is whether you need the REFCLKO feature.

For further reference, see the LAN8720A datasheet.