I am working on a video scaler chip which has multiple inputs (i.e HDMI, DP, VGA) but I only want to use the VGA input. (Choosing another chip with only one input is not an option).
The friendly datasheet did not mention any instruction on what to do with unused pins, so I tried searching the internet and the forums, below are the items I got. (If I got them right)
- Digital pins - tie to Vdd/Gnd with pull-up or pulldown
- Analog pins - tie to DC potential
And based on my search, the configuration (where to pull) for the lowest power consumption will vary per IC.
I was about to just pull down the DP and HDMI receiver pins (analog) to mimic a DP/HDMI port that is not connected to any source (standby). But then I realized there are these receiver VDD and VSS pins that I do not know what to do. DP, HDMI (as well as VGA) each have their own VDD and VSS pins (e.g. DP_VSS, DP_VDD). The datasheet mentions in the pin list tables that XX_VSS* 'must' be connected to ground, XX_VDD 'must' be bypassed with cap to ground. (XX - DP/HDMI/VGA) I assumed the 'must' is mentioned in the datasheet so that the DP or HDMI receiver would work. (But I will not use them)
I was thinking, since they apparently have independent VDD and VSS for each receiver type (DP,HDMI,VGA), each receiver pin type is powered by independent XX_VSS and XX_VDD. So, If I leave the power pins of an unused feature floating, no power will be given to receiver pins of that feature, and that feature will be totally shutoff, hence, I might not need to pullup/pulldown the pins. Note though that the chip itself has its core and ring VDD and VSS.
If I will not use DP and/or HDMI, is it safe to leave their power pins floating? And if I would leave their power pins floating, is it safe to leave the analog receiver pins floating as well?
Or should I connect the power pins and then pulldown(or up) the analog input pins?
Which configuration would have the lowest power consumption (in general)?
I tried contacting the website for this chip, but they can't give technical support anymore because this is already a legacy chip. I am working on an STDP60XX.
(P.S. I am new to the stackexchange, if I've missed some rules, please let me know and I'll edit my question immediately. Thanks)