I’m developing a custom carrier board based on the Jetson carrier board, and I’m looking at the SD card power switch (p11 of the schematics). The board uses the APL3511DBI here, in contrast to the APL3511CBI used on the USB circuit. The difference is that the DBI version’s enable pin is active low, but the CBI is active high. The USB’s enable pin is connected directly to the Jetson, but the SD card uses a FET to invert the signal to drive the active low switch with an active high from the chip.

Is the SDCARD_VDD_EN a 1.8V signal or 3.3V? It being a 1.8V signal is the only reason I can see to use the arrangement described above, because the minimum On level is 2V. If it’s 3.3V, I can skip the FET, use the CBI version of the switch (or the TI TPS2051BDBVR I’m using instead) and just drive the enable pin directly.

I note that all the other SD card lines are connected directly without a level shifter, so it looks like a 3.3V interface, but I want to be sure.

Hi, SDCARD_VDD_EN is a 1.8V signal. APL3511DBI is low enable, so use the FET to invert enable signal.