MAXREFDES1246: ±10V or ±20mA 4-Channel Universal Analog Input Using the MAX11270


Reference Design Disclaimer See the  Important Notice and Disclaimer  covering reference designs and other Maxim resources.


The MAXREFDES1246 is a 4-channel universal analog input that measures voltage or current signals. Each channel can be configured for voltage input at -10V to 10V or current input at -20mA to 20mA. A 24V power supply can be switched out to power an external 2-wire, 3-wire, or 4-wire sensor.

The MAXREFDES1246 provides a complete system solution for industry voltage and current measurement. The analog front end (AFE) includes Beyond-the-Rails analog switches, and operational amplifiers are used to achieve voltage/current input selection and signal conditions. The 24-bit MAX11270 analog-to-digital converter (ADC) is the heart of the system and achieves highly accurate measurement.

The microcontroller communicates with MAX11270 and MAX7317 10-port I/O expander to control the AFE and accept ADC conversion results. The 24V field input power supply is isolated with the AFE and with the microcontroller, which is powered by a USB power supply. This isolated design enhances system robustness in harsh industry applications.

The MAXREFDES1246 also integrates five Beyondthe- Rails SPDT analog switches (MAX14763), a dual Beyond-the-Rails 4:1 analog multiplexer (MAX14778), two ultra-precision, low-noise op amps (MAX44251), 2.75kVRMS data isolators (MAX14930 and MAX14932), a STM32F1 microcontroller, a microprocessor supervisory circuit (MAX6730), a FTDI USB-UART bridge, a high-efficiency iso-buck DC-DC converter (MAX17681), and isolated/regulated +5V and +3.3V power rails (two MAX16910s) and a -5V power rail (MAX1697). The entire system typically operates at less than 500mW and fits into a 5cm x 10.6cm space. While targeted for industrial PLC applications, the MAXREFDES1246 can be used in any application that requires high-accuracy analog-to-digital conversion.


  • High accuracy measurement
  • -10V to +10V voltage inputs
  • -20mA to 20mA current inputs
  • Four channels
  • Each channel can be configured as voltage or current input
  • 24V input protection
  • Isolated power and data
  • Board calibration
  • Connector provides 24V output
  • 24V output enable or disable


Designed, Built, Tested

Board pictured here has been fully assembled and tested. Not available for sale.


Maxim Devices (1)

Part Number Name Product Family Order Design kits and evaluation modules
MAX11270 24-Bit, 10mW, 130dB SNR, 64ksps Delta-Sigma ADC with Integrated PGA Analog-to-Digital Converters Buy Now Design Kits

Maxim Devices (1)

Part Number Product Family
Analog-to-Digital Converters
24-Bit, 10mW, 130dB SNR, 64ksps Delta-Sigma ADC with Integrated PGA

Design Files (4)

Title Type Size Date
MAXREFDES1246 - Design Verification Testing PDF 529KB 2019-08-08
maxrefdes1246-pcb PDF KB 2019-08-08
maxrefdes1246-bom PDF 134KB 2019-08-08
maxrefdes1246-schematic PDF 63KB 2019-08-08
Date Type

MAXREFDES1246 - Design Verification Testing

(PDF, 529KB)






(PDF, 134KB)



(PDF, 63KB)

MAXREFDES1246 Related Videos

View All Videos