DS1868 Digital Pot Questions
Greg Norton
Posts: 70
Hello All,
I have a circuit using a DS1868 digital pot (datasheet attached). I have it setup as a simple voltage divider, with the high connection of the pot connected to +5v, and the low connection to ground. Somehow when the position of the wiper is set to 0, the voltage briefly goes to 0 but then jumps up to about 0.15v where it will stay until there is more activity on the wiper. I cannot determine the source of this behavior. I have two theories/guesses:
1. Wiper resistance. The datasheet says 400-1000 ohms of resistance. But I'm using the 100k version, so even if it was a worst case 1000 ohms the voltage should not be this high.
2. Without thinking about it, I have left the Vb input unconnected. Can someone explain the function of this input? Could it be related to what I am seeing? What should I connect this pin to?
Any inputs are appreciated.
Greg
EDIT:
Wow - I know I'm getting old when I can't even remember that I previously posted this question.· Somehow the answer I got last time didn't make it from my brain onto the circuit board.· Oh well, sorry folks.
Post Edited (Greg Norton) : 9/11/2007 5:16:26 PM GMT
I have a circuit using a DS1868 digital pot (datasheet attached). I have it setup as a simple voltage divider, with the high connection of the pot connected to +5v, and the low connection to ground. Somehow when the position of the wiper is set to 0, the voltage briefly goes to 0 but then jumps up to about 0.15v where it will stay until there is more activity on the wiper. I cannot determine the source of this behavior. I have two theories/guesses:
1. Wiper resistance. The datasheet says 400-1000 ohms of resistance. But I'm using the 100k version, so even if it was a worst case 1000 ohms the voltage should not be this high.
2. Without thinking about it, I have left the Vb input unconnected. Can someone explain the function of this input? Could it be related to what I am seeing? What should I connect this pin to?
Any inputs are appreciated.
Greg
EDIT:
Wow - I know I'm getting old when I can't even remember that I previously posted this question.· Somehow the answer I got last time didn't make it from my brain onto the circuit board.· Oh well, sorry folks.
Post Edited (Greg Norton) : 9/11/2007 5:16:26 PM GMT
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