MAX31911

Industrial, Octal, Digital Input

Translator/Serializer

General Description

The MAX31911 industrial interface serializer translates,

conditions, and serializes the 24V digital output of sen-

sors and switches used in industrial, process, and build-

ing automation to 5V CMOS-compatible signals required

by microcontrollers. It provides the front-end interface cir-

cuit of a programmable logic controller (PLC) digital input

module. The device features integrated current limiting,

lowpass filtering, and channel serialization. Input current

limiting allows a significant reduction in power consumed

from the field voltage supply as compared to traditional

discrete resistor-divider implementations. Selectable on-

chip lowpass filters allow flexible debouncing and filter-

ing of sensor outputs based on the application. On-chip

serialization allows a drastic reduction in the number of

optocouplers used for isolation. The device serializer is

stackable so that any number of input channels can be

serialized and output through only one SPI-compatible

port. This reduces the number of optocouplers needed

to only three, regardless of the number of input channels.

For enhanced robustness with respect to high-frequency

noise and fast electrical transients, a multibit CRC code

is generated and transmitted through the SPI port for

each 8 bits of data. 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, Maxim Integrated offers

a pin-compatible version of this device, the MAX31910.

The MAX31910 uses patent-pending circuit techniques to

achieve further reduction of power beyond what is pos-

sible by input current limiting alone.

The future generation version of the MAX31910 and

MAX31911 will include energy-less LED drivers while

maintaining pin compatibility.

Features

S

Eight High-Voltage Input Channels (36V max)

S

Configurable for IEC 61131-2 Input Types 1, 2, 3

S

Wide Operating Supply Range of 7V to 36V

S

Optional Configuration Allows 5V Supply

S

Selectable Input Filtering and Debouncing from

0ms to 3ms

S

Configurable Input Current Limiting from 0.5mA

to 6mA

S

High HBM ESD Immunity on All Field Input Pins

S

On-Chip 8-to-1 Serialization with SPI Interface

S

On-Chip 5V Regulator

S

Overtemperature Indicator

S

On-Chip 24V Field Supply Voltage Monitor

S

Low Quiescent Current and Power Dissipation

S

Multibit CRC Code Generation and

Transmission for Error Detection and More

Reliable Data Transmission to an External Micro

Applications

Digital Input Modules for PLCs

Industrial, Building, and Process Automation

Motor Control

Block Diagram

19-6441; Rev 1; 9/12

Ordering Information appears at end of data sheet.

EVALUATION KIT AVAILABLE

SOUT

CS

MODESEL

SIN

DB1

DB0

FAULTB

5VOUT

RIREF

GND

RT0

IN0

RT7

IN7

VREF

INPUT CHANNEL 0

VREF

SENSORS

24V

OR

CRC GEN.

µCONTROLLER

OR

ISOLATION

5V

5V REGULATOR

INPUT CHANNEL 7

SUPPLY

MONITOR

TEMP

MONITOR

CURRENT

LIMITER

LP

FILTER

CLK

VOLTAGE

COMPARATOR

SERIALIZER

MAX31911

For pricing, delivery, and ordering information, please contact Maxim Direct at

1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.