[SI-LIST] Isolation between +3.3V & +3.3V AUX supplies (section 3.2.5 of ExpressCard Standard)

  • From: Bharathkumar Raju <bharathrajupcb@xxxxxxxxxxx>
  • To: Signal Integrity <si-list@xxxxxxxxxxxxx>
  • Date: Sun, 14 Dec 2008 21:38:05 +0530 (IST)

Dear SI membsers,
 
                We are designing a USB based module for the 
ExpressCard interface.
1. Our device require about 400 mA for full functionality. Hence +3.3V AUX 
supply alone is not sufficient for our device functionality.
2. We need to support remote wake up so we need the +3.3V AUX supply. 
 
                    Can we tap both the +3.3V and +3.3V AUX 
supply for our device. We will provide a diode (Make : On Semiconductor, Part 
number : MBR0520LT1G) in the +3.3V supply to isolate the 2 power rails. 
 
1.Anode of this diode will be connected to the +3.3V (PIN numbers 14 & 15) and 
the cathode of this diode will be connected to the +3.3V AUX supply (pin number 
12). 
2. The device can draw power from both +3.3V and +3.3V AUX rails. 
3. With this arrangement, required power will be available and remote wake up 
is also possible.
4. During suspend state, the +3.3V AUX power supply cannot flow into the +3.3V 
supply as this will be blocked by the reverse biased diode. 
 
                    I hope this is an acceptable design and will 
comply with ExpressCard specification. The diode will provide necessary 
isolation, is this correct?



Bharath


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  • » [SI-LIST] Isolation between +3.3V & +3.3V AUX supplies (section 3.2.5 of ExpressCard Standard) - Bharathkumar Raju
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