For new designs, please refer to MAX22195 ›
The MAX31914 translates and conditions the 24V digital
output of sensors and switches used in industrial,
process, and building automation to 5V CMOS-compatible
signals required by microcontrollers. It provides the frontend
interface circuit of a programmable logic controller
(PLC) digital input module.
The signal voltage translation is performed in conjunction
with input current limiting and lowpass filtering. Input
current limiting allows a significant reduction in power
consumed from the field-supply voltage, as compared
to traditional discrete resistor-divider implementations.
To achieve the lowest in-class power dissipation, the IC
uses patent-pending circuit techniques to achieve further
reduction of power dissipation beyond what is possible
by input current limiting alone. This special low-power
operating mode is automatically activated when on-chip
lowpass filtering is selected.
Selectable on-chip lowpass filters allow flexible debouncing
and filtering of sensor inputs based on the application.
When no filtering is selected, the IC is capable of detecting
pulses as short as 0.75μs at its field inputs.
All 8 input channels are translated to CMOS logic levels and
presented in parallel on the eight output pins for direct or
galvanically isolated interface with a controller ASIC or
micro.
The on-chip 5V voltage regulator can be used to power
external optocouplers, digital isolators, or other external
5V circuitry.
For low-cost applications, Maxim Integrated offers a pin
compatible version of this device, the MAX31915, which
does not include the current-switching circuitry included
in the MAX31914.
Applications
- Digital Input Modules for Programmable Logic Controllers (PLCs)
- Industrial Automation, Building Automation
- Process Automation
