For new designs, please refer to MAX22195 ›
The MAX31915 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.
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
are 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 ultra-low-power applications and lowest possible heat
dissipation, Maxim Integrated plans to offer a pin-compatible
version of this device; the MAX31914. The MAX31914
uses patent-pending circuit techniques to achieve further
reduction of power beyond what is possible by input
current limiting alone. Contact the factory for availability.
Applications
- Digital Input Modules for Programmable Logic Controllers (PLCs)
- Industrial Automation, Building Automation
- Process Automation
