The TIDA-00809 TI design showcases a cost optimized architecture that improves resolution of a binary input module. A microcontroller unit (MCU) is shared between two input channels (group isolation) to minimize the cost per channel. Wide input range is covered using an amplifier with gain and a MCU integrated 10-bit analog-to-digital converter (ADC) to measure with in ±3% accuracy. This architecture eliminates the need for multiple hardware versions based on input voltage range as is the case with an opto-coupler based topology. A digital isolator is used to communicate the ADC code or the root-mean-square estimate of the input to the host processor. The design is tested for ESD, EFT and Surge as per IEC61000-4 Level 4.
- Measurement accuracy: <±3% over a wide input range for AC/ DC input using 10-bit SAR ADC
- MCU shared between two channels (group isolation) to minimize cost per channel with additional unassigned input channels for larger channel count group isolation
- Wide input range covered using an amplifier with two gain stages
- Choice of basic or reinforced isolation between input and the host processor using digital isolator
- Onboard current pulse generator (20mA-50mA, 50ms) using MCU PWM output to remove the contamination (anti-burnishing) on the binary input contacts