SOM Jumper Setting
The phyCORE-AM654x SOM has a series of power domain jumpers. What is the default position of the jumpers and what do they do?
The default configuration is noted in the phyCORE-AM65x SOM schematic. For example, J5 has a small 2+3 note below the jumper pads to show the current default setting:
Below is a description of what AM65x Power solder jumpers do:
These solder jumpers set their connected power domains to be supplied by either 1.8V or 3.3V. The 2+3 setting shown in the schematic is the current default setting, which means the signals under these domains are all currently set to 3.3V operation. Please note that not all domains have a jumper setting, PHYTEC decided on a few domains that we thought might be helpful to provide a 1.8V vs. 3.3V option (for example, the PRU signals). The TI AM65 datasheet should be referenced to determine exactly which I/Os this impacts.
These solder jumpers power the "IO bias supplies" that match up with the power domains mentioned above. As noted in the schematic, each one of these must match the listed jumper (i.e. J3 and J10 must be set to the same setting). This is a requirement of the AM65.
To give you an idea of how these jumpers work and how they can be configured, basically there are two configurations:
1) VDDSHVx power domain is configured for 3.3V operation; the corresponding VDDSx bias supply should be supplied from an "I/O Bias LDO" which is generated internally from the AM65.
2) VDDSHVx power domain is configured for 1.8V operation; the corresponding VDDSx bias supply should be supplied from the same source.
For an example, if we look at J3 and J10.
- J3 determines if the VDDSHV3 domain is set for 3.3V or 1.8V. It is set for 3.3V operation, therefore, VDDS3 must be sourced from the I/O bias LDO. This means that J10 should be set to 2+3.
- If VDDSHV3 was set for 1.8V instead, then VDDS3 must be sourced from the same VCC_1V8_IO power rail (which correlates to a J10 setting of 1+2).
For additional information: