# Quick Test of an ADC

I have an 8BIT MAX160 Analog Digital converter I am using in several boards. I was wondering if there was a way to quickly test the accuracy of the ADC and output range of the ADC to verify bit errors, etc.

My idea was to increase the incoming analog signal one bit "count" in magnitude for each iteration in a loop:

ADC Input range 0 - 4.00 VDC

calculated mV/Count: 0.015625

Example:

Analog Input (VDC)      Expected Output

0.00            00000000
0.015625        00000001
0.03125         00000010
0.0625          00000100
0.125           00001000
0.25            00010000
0.50            00100000
1.00            01000000
2.00            10000000
4.00            11111111


Test method:

Start at 0VDC to see if any "stuck" bits/lines are present.

Do a "walking 1" for each successive magnitude bit position

Then do 4.0 Max input for All 1's

My question is, would this be a valid "quick" test to run an ADC through, instead of doing every possible input value from 0 to 255?

• google.com/search?q=adc+characterization – Ignacio Vazquez-Abrams Jan 24 '14 at 16:03
• It's a test but there are plenty of other tests – Andy aka Jan 24 '14 at 16:04
• @Andy aka I've been having trouble finding "Common" failure modes of ADCs. – zacharoni16 Jan 24 '14 at 16:08
• Sure, that would work... But how do you plan on controlling the voltage down to 6 decimal places? – Adam Head Jan 24 '14 at 16:15
• Try looking for ADC performance testing instead. – Andy aka Jan 24 '14 at 16:18

## 2 Answers

Expecting a test input signal to produce a bit-accurate ADC output seems unreasonable. Instead you could create an exponential input voltage by turning on charging a capacitor through a resister. After reading in many period results over the expected rise time it shouldn't be hard to apply a test on the data comparing it to the easily predicted results for a gross ACD malfunction. At the very least it should be monotonically increasing and secondarily the delta between sample N and sample N+1 should be decreasing as N increases.

I have tested ADCs exactly that way, but you do need a very accurate voltage standard, and then you need to hunt a little, go a little high and a little low until you get the ADC output exactly that one bit.