Circuit Advice Sought

[beb101]

I am using this DPDT USB switch,
http://www.fairchildsemi.com/ds/FS/FSUSB42.pdf

The application is for charging a Dell Venue 8 Pro tablet. This tablet charges from a 2.1A source according to the "dumb" USB charging spec.; e.g. D+ D- shorted. In normal usage, the tablet locks out any I/O on the USB port while charging. There is a long thread here on how to use peripherals while charging,
http://forum.tabletpcreview.com/dell/59328-venue-8-usb-power-same-time.html

Basically, it was found that if charging is started with D+, D- shorted and then input to the USB port was switched to a source with a 1.5K to 1.8K resistor across D+, D- it would fool the tablet into accepting input. This function is easily handled by connecting HSD1+ and HSD1- and putting a resistor across HSD2+/HSD2-. My question concerns management of the switching function. I want a small delay before switching to HSD2 from HSD1 upon toggling the SEL from low to high. Our friend the 08m2 can easily handle this. But, is there any way of doing it with discrete logic? I was thinking of a RC time delay as input to a 74LVC2G14 Schmitt trigger inverter connected to the SEL input.

 

[techElder]

You could probably use an 08M2 like a 555 timer IC set up with a one-shot delay of whatever time you wanted. Its a VERY simple program for the 08.

I would work with the 08M2 and a CMOS CD4066 Quad Bilateral switch to make the DPDT switch. Create a program with Q and NOT Q outputs like a flip-flop to switch "opposite" 4066 switches after a timed delay of your choice.

Two components ... no time constant components ... plenty more programming room for blinky LEDs and other fluff.