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- 16-Bit 8-Channel Software-Configurable Analog Input Module for PLCs Design Guide (Rev. B)
(PDF 7745 KB)
17 Sep 2014 1,878 views
This reference design provides a complete solution for a single supply industrial control Analog Input Module. The reference design is suitable for process control end equipment like Programmable Logic Controllers (PLC), Distributed Control system (DCS), Data Acquisition Systems (DAS) modules that must digitize standard industrial current inputs and bipolar or unipolar input voltage ranges up to ±10V.
In an industrial environment the analog voltage and current ranges typically include ±2.5 V, ±5 V, ±10 V, 0 V to 5 V, 0 V to 10 V, 4 mA to 20 mA, and 0 mA to 20 mA. This reference design can measure all standard industrial voltage and current inputs. Eight channels are provided on the module and each channel can be configured as a current or voltage input with software configuration. The SAR based architecture of ADS8688 leverages better sampling rate. The ADS8688 also includes an on-chip PGA. The on-chip PGAs are used to provide gain and level shift the bipolar signals. The ISO7141 & ISO1541D provides digital signal isolation between host microcontroller and measurement side. The power isolation has been achieved using LM5017 based Flybuck transformer. The module has on-board EEPROM to store calibration data and module configuration data. This reference design also demonstrate the TI products like hot swap & in-rush current limit controller, isolated Flybuck controller, low noise LDO, and I2C to GPIO expander that can be used in the entire PLC signal processing chain. The module has been designed to be pluggable to the IO Controller (TIDA-00123) for quick testing & evaluation. The module reference design also includes external protection circuit and has been tested and verified to be compliant with IEC61000-4 standards – EFT, ESD and Surge requirements with IO Controller platform.
- 8 channel, 16 bit SAR ADC ADS8688 that supports from 300ksps to 30ksps per channel
- Programmable channels: Each channel can be configured as current or voltage input with software configuration
- Programmable Current Range (0-20mA) and Voltage range (+/-10V)
- Single 24V input power supply operation
- Designed for IEC-61000 compliance (IEC-61000-4-4: EFT up to ±2KV @ 5KHz on signal ports; IEC-61000-4-2: ESD up to 4KV contact & 8KV air discharge; IEC-61000-4-5: Surge up to ±1KV line-earth (CM) on signal ports)