This is a complete reference design for a multi-channel sensing solution for applications such as temperature controllers, data loggers, programmable logic controller (PLC) analog inputs, etc. Isolation between digital and analog components (and among channels) eliminates noise interference and works to keep the analog-to-digital converter (ADC) results accurate.

System Benefits:

  • Complete combination of microcontroller (sensor analog front-end (AFE) and signal conditioning), buck regulator, and isolation photocoupler with microcontroller (MCU) reference software
  • MCU with AFE for sensing
    • Reduces main MCU workload
    • Flexible communication through 3-wire SPI interface
    • Simple timing design for simultaneous multi-channel sensing
  • Photocoupler isolation
    • Long isolation distance
    • No noise emission



Winning Combinations Interactive Diagram

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4:3 ratio Sheet.63 Sheet.64 Sheet.1 Sheet.2 Sheet.3 Sheet.4 JP141 JP141 JP141 LDO LDO LDO Transformer Transformer Transformer Buck Regulator Buck Regulator Buck Regulator Power Supply 24V Power Supply 24V Power Supply 24V Thermocouple Thermocouple Thermocouple Thermocouple x3 Thermocouple x3 Thermocouple x3 Channel 2 Channel 2 Channel 2 Main MCU Main MCU Main MCU Channel 3 Channel 3 Channel 3 Channel 4 Channel 4 Channel 4 Sheet.28 Sheet.32 Photocoupler 1 Photocoupler Photocoupler Photocoupler 2 Photocoupler Photocoupler Channel 1 Channel 1 Channel 1 Sensor Sensor Sensor Sensor Sensor Sensor 5V 5V 5V To Photocoupler To Photocoupler To Photocoupler Isolation Isolation Isolation SCK SCK SCK MOSI MOSI MOSI MISO MISO MISO To Main MCU (SCK, MOSI, MISO) To Main MCU (SCK, MOSI, MISO) To Main MCU (SCK, MOSI, MISO) Sheet.48 Sheet.49 Sheet.50 Sheet.51 Sheet.52 Sheet.53 Sheet.54 Sheet.55 Sheet.56 Sheet.57 Sheet.58 Sheet.59 Sheet.60 Sheet.61 Connector 1.160 MCU MCU MCU MCU CPU CPU CPU SPI SPI SPI ADC ADC ADC Sheet.76 Peripheral Op Amp Comparator Sheet.69 Sheet.70 Driver Sheet.72 Sheet.73 Sheet.74
Exiting Interactive Block Diagram