SN74CB3Q3245 HOT SWAP

Thanks Chris, this was very helpful.

Chris,

Quick question. What is the order for which VBIAS and VCC must be applied to the SN74CBT6845C?  I’ve seen some pre-charge devices that require VBIAS first,  others that want them simultaneous, and even some others that require a diode/resistor between the VBIAS and VCC to prevent a latch-up condition?

Here is the order.  Gnd and Bias first and they can be connected at the same time.  This is shown in the level 3 Slide.

1. gnd       2. bias Vcc           3. I/O's    4. Vcc

Chris,

Is there a certain sequence that needs to be taken for the SN74CB3Q3245 on the voltage aspect of things if used for hot-swap?

not really. Gnd first always if possible.  Vcc next if possible.  If not  possible then at all at the same time will work. 

Chris,

Sorry about the parade of questions, but on the SN74CBT6845 can the Vcc be applied >200ms after active bus signals are already applied to I/O using 5V output. Thanks for the help.

I should be OK as long as Vcc bias is up first. Then when Vcc is brought up the OE should be in the disable state.

Chris,

The datasheet really doesn't seem to specify this type of questioning. Last question, I promise, does the Vcc on the '3245 have to be on before the I/O's? I apologize again for the rampage.

Perfect! Thanks Chris.