Maxim > Design Support > Technical Documents > Application Notes > A/D and D/A Conversion/Sampling Circuits > APP 633
Keywords: ADC, characterization, INL, DNL, gain, offset, channel coupling and matching, National
Intruments, NI, Labview, PC, DAQ, analog to digital converters
APPLICATION NOTE 633
Bench Characterization of ADCs Using a Low-Cost
PC-Based Data-Acquisition Board
May 20, 2002
Abstract: This application note describes techniques of using a PC based Digital I/O Board to
characterize analog-to-digital converters (ADCs). It will look at static DC parameters such as integral
nonlinearity (INL), differential nonlinearity (DNL), gain, and offset errors, but also noise, internal reference
voltage, and channel-to-channel coupling and matching, as well as the supply voltage dependence.
With the increasing complexity of analog-to-digital converters (ADCs), it is becoming more difficult to
analyze and characterize these devices in a lab environment. One way to improve the thoroughness of
characterization with ADCs is to use a PC to automate the bench testing. This approach has many
advantages, which arise with little additional effort. The most important benefit of using automation in
place of manual testing is obtaining a more complete view of the converter's performance much earlier in
the characterization process. Also, once the system is in place, designing vectors to debug even
complex design errors is usually straightforward.
There are a number of ways a PC can be used to automate characterization of an IC. They range from
using a simple parallel-port interface for manipulating control bits, to a closed-loop servo system for fully
characterizing all aspects of the device's performance. The following discussion will focus primarily on
the approach used to characterize the MAX1115-MAX1119 8-bit successive approximation register
(SAR) ADCs. This method is accurate enough to be used for characterizing similar converters with
resolutions up to 12 bits. Many of the issues associated with using parallel and serial ports to
characterize devices are covered in the article "PCs Provide The Key To Economical Yet Effective
Automated Test Systems," published in Electronic Design magazine.
System Setup
To characterize the MAX1115, a high-speed digital I/O card from National Instruments (PCI-DIO-32HS)
and a custom characterization board were used. The PCI-DIO-32HS 32-channel digital I/O board can be
used to stream vectors to (or from) a PC hard disk from (or to) the custom characterization board at a
rate of 20MHz. A schematic of the characterization board is shown below.
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