Level Shifters??

AA9GG

New member
My platform micro runs at 5v. What level shifter (5v<->3v) do you recommend for the CFAF800480E1-050SR display? The one I am currently using might be to slow. The 5v side looks fine, but the 3v side is HORRIBLE. On the SCK for example, 5v is a nice pulse train (say 10 pulses), the 3v side has a bit of noise with one BIG pulse and a few smaller ones in that time frame.
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I was thinking something without a direction control line, it should be transparent
So then you want something one-directional (5v -> 3v) instead of bi-directional (5v<->3v) as you indicated? In which case, what do you mean by 'transparent'? You could just use a resistive divider for one-way.
 

AA9GG

New member
So then you want something one-directional (5v -> 3v) instead of bi-directional (5v<->3v) as you indicated? In which case, what do you mean by 'transparent'? You could just use a resistive divider for one-way.
I'm assuming I need 5v<->3v. I know they make bi-directional parts without a DIR line. I guess I should have said automatic rather than transparent.
I mainly need it on the 3 SPI lines, chip select and power_dwn pins.
 
TXB0108 or TXS0108E. The 'automatic' ones tend to be a little bit slower propagation delay. You'll have to check data sheets for that style to see if they meet your needs.
 

AA9GG

New member
TXB0108 or TXS0108E. The 'automatic' ones tend to be a little bit slower propagation delay. You'll have to check data sheets for that style to see if they meet your needs.
Funny you mention those. I am actually trying to use the TXB0108. I am have a hell of a time trying to get the OE to work for some reason and that is why I was looking for other candidates. I have the pin to ground thru a resistor, like they said, but it is hit or miss. I even put the R box on it to find a value. Very strange issue. When it DOES work, the signals on both sides look BEAUTIFUL.
 
Does it make any difference if you drive the OE line from an unused port pin set low?

BTW, does AA9GG happen to be a call sign? I was a K8 back in the day.
 

AA9GG

New member
Does it make any difference if you drive the OE line from an unused port pin set low?
OE low puts it into tri-state, that works. My first thought was to just strap it to +3v, then I saw the note about a resistor to ground which seems strange for an enable line. Apparently the pin needs to be low until power stabilizes (we a talking nanoseconds). They don't give an R value, just that it depends on the supply current.

BTW, does AA9GG happen to be a call sign? I was a K8 back in the day.
Yes, it is my Amateur Radio Callsign
 

AA9GG

New member
I have found a conflict between the actual datasheet and the one for the eval board. It appears the OE pin should be connected to V+ via the resistor and NOT to ground. I also found a schematic on the 'net where it is indeed tied to V+. I will try it on Monday when I get to work...
 
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