Signal Conditioning Issues
In industrial applications, a digital-to-analog (D-to-A) interface may be rather straightforward but the analog-to-digital (A-to-D) converter (ADC) can be a challenge. The capacitive input stage of both delta-sigma and successive approximation register (SAR) interfaces used for the ADC requires signal capture within a limited time frame. An improper signal chain can cause ringing and oscillation and result in inaccurate readings. However, this is just one of many factors to consider when selecting an ADC.
Signal Chain
High-performance ADCs convert the output of an analog sensor to a digital format for a microcontroller or digital signal processor. The selection of the ADC must be part of a systems approach. “When somebody starts a design, you start with the sensor, you see what kind of output impedance it has and you choose an amplifier and resistors around the amplifier and you choose that configuration based on your sensor,” says Chuck Sins, applications engineer, National Semiconductor. “Based on the accuracy of your sensor and what you are ultimately trying to achieve, then I choose the resolution of the ADC.”
