I'm right now attempting to reverse-engineer a computer memory card. It is basically a SRAM card with a battery backup.
+5VDC is taken from the host system's expansion slot, and basically powers everything up, including the SRAM modules. When the +5VDC is no longer avai lable (i.e. the computer is turned off,) the battery saves the contents of the SRAM modules.The battery is used to protect the contents of the SRAM modules from gettin g lost. It is a 3V lithium battery, and is rechargable.
Between the VCC pin on the SRAM modules and the +5VDC rail from the host sy stem, there sits a diode I can only partially identify. On the diode, I can only read "3A" and "ITT". The cathode end connects to the SRAM VCC pin, wh ile the anode connects to the +5VDC rail. I believe the diode is being used to avoid the battery voltage from flowing into the host system.
What would be a good diode to use in this situation?