19 Jun
2011
19 Jun
'11
6:54 p.m.
However, I think there's one pretty serious problem in the hardware design: The bus switch has something like at least 5 (rather 16Ohms) of internal 'on' resistance between the sim card and the phone. While this _might_ still work for I/O, nRST and CLK lines, it definitely doesn't fly for the supply voltage (VCC).
Why not just keep the bus switch IC for the signals. ( ~ 20 ohms won't be a problem for sure ).
And use any PMOS with a pullup for the VCC switching ? Or you can even get fancy and use a dedicated load switch like the TPS22960 .
Cheers,
Sylvain