looking for a certain type of ADC - not sure if it exists, what it would be called, or the best way

[picobot]

Hi. Hope its ok to just pop in and ask a question like this.

I'm looking for something similar to an 8-bit ADC, except that instead
of having the normal bit output of an 8-bit binary number, 0-255, I
want only one bit to be high at a time - essentially for the output to
be quantized to 1,2,4,8,16,32,64 and 128 (00000001, 00000010, 00000100,
00001000, 00010000, 00100000, 01000000, 10000000).

The objective is to control a series of analog switches and
unfortunately due to the design of the circuit I'm interfacing with
here, I can only have one switch open at a time, therefore only one bit
of the ADC output high at a time.

Someone else out there must have needed this type of output in the past
but I haven't been able to find an IC that does it. Any suggestions
would be much appreciated.

Thanks
picobot

 

[picobot]

I think a 138 decoder will do the trick as you suggested.

Looks like I could also use a 3 bit ADC instead of the priority encoder
for the input going to this decoder.

Thanks much for the info.

picobot

 

[picobot]

Yea I was thinking that too last night...after realizing that a 3 bit
adc may be hard to find. I have some 8bit ADCs here already so I will
try to scale the analog input down to the range of the 1st 3 bits of
output.

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