MAX31910AUI+T - Maxim Integrated

19-6440; Rev 5; 4/15

Ordering Information appears at end of data sheet.

General Description

The MAX31910 industrial interface serializer translates,

conditions, and serializes 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 front-end interface

circuit of a programmable logic controller (PLC) digital

input module.

The device features integrated current limiting, lowpass

filtering, and channel serialization. Input current limit-

ing allows a significant reduction in power consumed

from the field voltage supply as compared to traditional

discrete resistor-divider implementations. In addition, to

achieve the lowest in-class power dissipation, the device

uses patent-pending circuit techniques to achieve further

reduction of power beyond what is possible by input

current limiting alone.

Selectable on-chip lowpass filters allow flexible debouncing

and filtering 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 low-cost applications, Maxim Integrated offers a

pin-compatible version of this device, the MAX31911.

The MAX31911 does not include the patent-pending

current clamp-switching circuitry that is included with the

MAX31910.

The MAX31912 and MAX31913 versions includes energy-

less LED drivers while maintaining pin compatibility.

Benets and Features

●Ultra-Low Power and Heat Dissipation

• Low Quiescent Current (1.4mA typ)

• Highly Accurate and Stable Input Current Limiters,

Adjustable from 0.5mA to 6mA

• Special (Patent-Pending) Ultra-Low-Power Mode

with Switched Current Limiters

●High Integration Reduces BOM Count, Board

Size, and System Cost

• 8 High-Voltage Input Channels (36V max)

• On-Chip 8-1 Serialization with SPI Interface

• On-Chip 5V Regulator

• On-Chip Overtemperature Indicator

• On-Chip Field Supply Voltage Monitor

• Integrated Debounce Filters, Selectable from 0 to 3ms

●Robust Features and Performance for Industrial

Environments

• Multibit CRC Code Generation and Transmission for

Error Detection and More Reliable Data Transmission

• High ESD Immunity on All Field Input Pins

●Accepts Industry Standard Input Types

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

●Flexible Power Supply Capability Enables Usage

in 5V, 12V, 24V, and Higher Voltage Systems

• Wide Operating Field Supply Range of 7V to 36V

• Can Be Powered From the Logic-Side Using a 5V

Supply

Applications

●Digital Input Modules for PLCs

●Industrial, Building, and Process Automation

●Motor Control

MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

EVALUATION KIT AVAILABLE

Block Diagram

SOUT

MODESEL

SIN

DB1

DB0

FAULTB

5VOUT

VCC24V

RIREF

GND

RT1

IN1

RT8

IN8

VREF

INPUT CHANNEL 0

VREF

SENSORS

24V

CRC GEN.

µCONTROLLER

ISOLATION

5V REGULATOR

INPUT CHANNEL 7

SUPPLY

MONITOR

TEMP

MONITOR

SWITCHED

CURRENT

LIMITER

FILTER

CLK

VOLTAGE

COMPARATOR

SERIALIZER

MAX31910

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

(Voltages relative to GND.)

Voltage Range on VCC24V ............................. -0.3V to +45V

Voltage Range on IN1–IN8 ............................ -0.3V to +45V

Voltage Range on IN1–IN8

(through 2.2kω resistors) ............................ -45V to +45V

Voltage Range on DB0/DB1, CLK, SIN,

CS, MODESEL .......................... -0.3V to (V5VOUT + 0.3V)

Continuous Power Dissipation (TA = +70NC)

TSSOP (derate 27mW/NC above +70NC) .......... 2162.2mW

Operating Temperature Range

Ambient Temperature.............................-40NC to +125NC

Junction Temperature ............................-40NC to +150NC

Storage Temperature Range ......................-55NC to +125NC

Lead Temperature (soldering, 10s) .........................+300NC

Soldering Temperature (reflow) ...............................+260NC

TSSOP

Junction-to-Ambient Thermal Resistance (qJA) ..........37°C/W

Junction-to-Case Thermal Resistance (qJC) ..................2°C/W

Absolute Maximum Ratings

Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer

board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-

tion of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute

maximum rating conditions for extended periods may affect device reliability.

Package Thermal Characteristics(Note 1)

Recommended Operating Conditions (Note 2)

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Field Supply Voltage VCC24V 7 36 V

Field Inputs Voltage VINn (Note 3) -0.3 36 V

Logic Inputs Voltage VLOGIC 0 5.5 V

Current-Limit Setting Resistor RREF 15 kI

Field Input Data Rate fIN (Note 4) 200 kHz

DC Electrical Characteristics

(VCC24V = 7V to 36V, TJ = -40NC to +150NC, unless otherwise noted.) (Note 2)

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

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PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Field-Supply Current ICC24V IN1–IN8 = 24V, 5VOUT = open,

RT1–RT8 = GND, all logic inputs open 1.4 2.2 mA

Field-Supply UVLO Off/On VONUVLO 9 10 V

Field-Supply UVLO On/Off VOFFUVLO 7 8 V

Field Input Threshold High-

to-Low VIN-(INF) 2.2kI external series resistor 6 7.5 V

Field Input Threshold Low-to-

High VIN+(INF) 2.2kI external series resistor (Note

11) 8.5 10 V

Field Input Hysteresis VHYS(INF) 2.2kI external series resistor (Note

11) 1 V

Input Threshold High-to-Low

(at IC pin) VTH-(INP) 2 2.5 V

Input Threshold Low-to-High

(at IC pin) VTH+(INP) (Note 11) 3.5 4 V

Input Threshold Hysteresis

(at IC pin) VHYS(INP) (Note 11) 1 V

Field Input Pin Resistance RINP 0.8 kI

Field Input Current Limit IINLIM RREF = 15kI, VCC24V = 18V to 30V

(Note 5) 2.2 2.4 2.6 mA

Filter Time Constant tFILTER

DB1/DB0 = 0/0: no filtering 0

DB1/DB0 = 0/1 0.008 0.025 0.038

DB1/DB0 = 1/0 0.25 0.75 1.1

DB1/DB0 = 1/1 1.0 3 4.5

Linear Regulator Output V5VOUT Max ILOAD = 50mA 4.75 5.0 5.25 V

Regulator Line Regulation dVREGLINE ILOAD = 50mA 10 20 mV

Regulator Load Regulation dVREGLOAD ILOAD = 1mA to 50mA 20 50 mV

Logic-Low Output Voltage VOL IOL = 4mA 0.4 1.0 V

Logic-High Output Voltage VOH IOH = -4mA 4.0 V

Logic-Input Trip Point VIH-IL 0.3 x

V5VOUT

0.5 x

V5VOUT

0.7 x

V5VOUT V

Logic-Input Leakage Current IIL -50 -30 -15 FA

Overtemperature Alarm TALRM 135 NC

Note 2: Limits are 100% production tested at TA = +25°C and/or TA = +125°C. Limits over the operating temperature range and

relevant supply voltage range are guaranteed by design and characterization. Typical values are not guaranteed.

Note 3: When using suggested external 2.2kω series resistors, limits of -3V to +36V apply.

Note 4: fIN refers to the maximum pulse frequency (1/fIN = shortest pulse width) that can be detected from the field sensors and

switches.

Note 5: External resistor RREF can be adjusted to set any desired current limit between 0.5mA and 6mA.

Note 6: See Figure 9.

Note 7: See Figure 6.

Note 8: See Figure 8.

Note 9: See Figure 7.

Note 10: This is the maximum bit transfer rate through the serializer interface.

Note 11: When input current switching is enabled (DB0/DB1 = 0), there is no input threshold hysteresis. In this case, the input

threshold for both falling and rising signals is the high-to-low threshold.

AC Electrical Characteristics: SPI Interface

(VCC24V = 7V to 36V, TJ = -40NC to +150NC, unless otherwise noted.) (Note 2)

AC Electrical Characteristics

(VCC24V = 7V to 36V, TJ = -40NC to +150NC, unless otherwise noted.) (Note 2)

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

CLK Pulse Duration tCLKPW (Note 6) 20 ns

CS Pulse Duration tCSPW (Note 7) 20 ns

SIN to CLK Setup Time tSU1 (Note 8) 5 ns

SIN to CLK Hold Time tH1 (Note 8) 8 ns

CS to CLK Setup Time tSU2 (Note 9) 8 ns

CS to CLK Recovery Time tREC (Note 9) 12 ns

Clock Pulse Frequency fCLK (Notes 6, 10) 25 MHz

Propagation Delay, CLK to SOUT tP1 (Note 6) 20 ns

Propagation Delay, CS to SOUT tP2 (Note 7) 20 ns

Rise/Fall Time SOUT/FAULT tR/F (Note 6) 40 ns

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Field Input Pulse Width tPW No external capacitors on pins IN1-

IN8 1µs

ESD HBM, all pins ±2kV

HBM, IN1-IN8 with respect to GND ±15

Typical Operating Characteristics

(TA = +25°C, RREF = 15kω, unless otherwise noted.)

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

POWER-SUPPLY CURRENT

vs. VCC24V FIELD SUPPLY

MAX31910 toc01

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

1.35

1.40

1.45

1.50

1.55

1.60

1.30

5152

SUPPLY CURRENT vs. TEMPERATURE

MAX31910 toc02

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

6010

1.45

1.50

1.55

1.60

1.40

-40

CURRENT LIMIT vs. RREF

MAX31910 toc03

RREF (kI)

CURRENT LIMIT (mA)

40302010

5.5

0.5

1.5

2.5

3.5

4.5

INPUT CURRENT LIMIT

vs. TEMPERATURE

MAX31910 toc04

AMBIENT TEMPERATURE (°C)

CURRENT LIMIT (mA)

1106010

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3.0

2.0

-40

VINn = 24V

INPUT CURRENT LIMIT

vs. FIELD INPUT VOLTAGE

MAX31910 toc05

FIELD INPUT VOLTAGE (V)

CURRENT LIMIT (mA)

352515

0.5

1.0

1.5

2.0

2.5

3.0

VCC24V = 24V

INPUT VOLTAGE HYSTERESIS

vs. TEMPERATURE

MAX31910 toc06

TEMPERATURE (°C)

THRESHOLD VOLTAGE (V)

1106010

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0

2.0

-40

OFF-ON THRESHOLD

ON-OFF THRESHOLD

RIN = 0I

INPUT VOLTAGE HYSTERESIS

vs. TEMPERATURE

MAX31910 toc07

TEMPERATURE (°C)

THRESHOLD VOLTAGE (V)

1106010

7.2

7.4

7.6

7.8

7.0

8.2

8.4

8.6

8.8

9.0

7.0

-40

OFF-ON THRESHOLD

ON-OFF THRESHOLD

RIN = 2.2I

LDO LOAD REGULATION

MAX31910 toc08

5VOUT OUTPUT CURRENT (mA)

5VOUT VOLTAGE (V)

4.92

4.94

4.96

4.98

5.00

5.02

5.04

5.06

5.08

5.10

4.90

040 50302010

LDO LINE REGULATION

MAX31910 toc09

SUPPLY VOLTAGE (V)

5VOUT VOLTAGE (V)

4.92

4.94

4.96

4.98

5.00

5.02

5.04

5.06

5.08

5.10

4.90

6363126211611

I5VOUT = 5mA

Typical Operating Characteristics (continued)

(TA = +25°C, RREF = 15kω, unless otherwise noted.)

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

LDO LINE REGULATION

MAX31910 toc10

SUPPLY VOLTAGE (V)

5VOUT VOLTAGE (V)

4.92

4.94

4.96

4.98

5.00

5.02

5.04

5.06

5.08

5.10

4.90

6363126211611

I5VOUT = 50mA

LDO OUTPUT VOLTAGE

vs. TEMPERATURE

MAX31910 toc12

AMBIENT TEMPERATURE (°C)

5VOUT VOLTAGE (V)

4.92

4.94

4.96

4.98

5.00

5.02

5.04

5.06

5.08

5.10

4.90

-40 1106010

I5VOUT = 0mA

LDO OUTPUT

vs. VCC24V FIELD SUPPLY

MAX31910 toc11

SUPPLY VOLTAGE (V)

5VOUT OTPUT VOLTAGE (V)

4.6

4.7

4.8

4.9

5.0

5.1

5.2

5.3

5.4

5.5

4.5

4342414

I5VOUT = 50mA

LDO OUTPUT VOLTAGE

vs. TEMPERATURE

MAX31910 toc13

AMBIENT TEMPERATURE (°C)

5VOUT VOLTAGE (V)

4.92

4.94

4.96

4.98

5.00

5.02

5.04

5.06

5.08

5.10

4.90

-40 1106010

I5VOUT = 5mA

Pin Description

Pin Conguration

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

PIN NAME FUNCTION

1, 2 DB0, DB1 Debounce (Filtering) Time Select Inputs. These inputs also determine the current

switching frequency. See Table 1 for details.

3, 5, 7, 9, 11, 18,

20, 22 IN1–IN8 Field Inputs

4, 6, 8, 10, 12,

17, 19, 21 RT1–RT8 Connect directly to GND. These pins are reserved for energy-less LED drivers in future

versions of the device.

13 RIREF Current-Limiter Reference Resistor

14 VCC24V Field-Supply Voltage

15 5VOUT 5V Regulator Output

16 FAULT Active-Low Overtemperature or Undervoltage Alarm

23 SOUT Serial-Data Out

24 CS Active-Low Chip-Select Input

25 CLK Serial-Clock Input

26 MODESEL

Mode-Select Input

MODESEL = 1: Selects 8-bit shift register

MODESEL = 0: Selects 16-bit shift register

27 SIN Serial-Data Input

28 GND Field Ground

— EP Exposed Pad. Must be connected to the PCB ground plane.

TOP VIEW

MAX31910

254CLKRT1

263 MODESELIN1

272 SIN

DB1

281 +GNDDB0

227 IN8

IN3

236 SOUTRT2

218 RT8RT3

209 IN7IN4

1910 RT7RT4

1811 IN6IN5

1712 RT6RT5

13 FAULTRIREF

245 CS

IN2

1514 5VOUTVCC24V

Basic Application Circuit

Detailed Description

Input Current Clamp

The MAX31910 industrial interface serializer inputs (IN1–

IN8) sense the state (on vs. off) of field sensors by moni-

toring both voltage and current flowing through the sen-

sor output. The current sinking through these input pins

rises linearly with input voltage until the limit set by the

current clamp is reached. Any voltage increase beyond

this point does not increase the input current any further.

The value of the current clamp is adjustable through an

external resistor connected between the RIREF pin and

GND. Pins RT1–RT8 must be connected directly to GND

to provide a return path for the input current. The volt-

age and current at the IN1–IN8 input pins are compared

against internally set references to determine whether the

sensor is on (logic 1) or off (logic 0). The trip points deter-

mining the on/off status of the sensor satisfy the require-

ments of IEC 61131-2 Type 1 and 3 switches. The device

can also be configured to work as a Type 2 switch.

Glitch Filter

A digital glitch filter provides debouncing and filtering

of noisy sensor signals. The time constant of this filter is

programmable from 0ms to 3ms through the DB0 and

DB1 pins. See Table 1 for debounce settings.

To provide the digital glitch filter, the device checks that

an input is stable for at least three clock cycles. The dura-

tion of a clock cycle is 1/3 of the selected debounce time.

If the input is not stable for at least three clock cycles,

the input change is not sent to the internal shift register.

Low-Power Current Clamp Switching

The MAX31910 uses a patent-pending switched cur-

rent limiter to reduce power consumption below what is

achievable by current limiting alone (Figure 1). The inter-

nal filter clock is used to switch input current between

100% and 20% of the chosen current limit. For example,

if the current limit is set to 2.4mA, the input current

switches between 2.4mA and 0.48mA. The switching is

done at a controlled ramp rate of tDELAY (0.5µs typ). The

filter clock switches input current at a 50% duty cycle.

The clock period for current switching is automatically

selected by the DB1 and DB0 glitch filter settings. See

Table 1 for current switching settings.

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

GND

MODESEL

DB1

DB0

5VOUT

SIN

CLK

SOUT

FAULT

CLK

SOUT

FAULT

ISOLATION

JUMPERS TO

5VOUT

AND GND

VDD_LOGIC

RREF

RINX

24V

fIN1–8

RIREF

IN1–8

RT1–8

VCC24V

MAX31910

NOTE: SEE FIGURE 1 FOR ADDITIONAL COMPONENTS NEEDED FOR EMC.

Table 1. Debounce Settings

Powering the Device Through the 5VOUT Pin

The device can alternatively be powered using a 5V

supply connected to the 5VOUT pin. In this case a 24V

supply is no longer needed and the VCC24V supply must

be kept unconnected (see Figure 2).

In this configuration, the device will always indicate

a UVFAULT and the FAULT pin will always be active

(pulled low). Faults due to the supply voltage monitoring

will not be available. Faults due to the temperature monitor

can only be read through the SPI interface.

This configuration has a lower power consumption and

heat dissipation since the on-chip 5V voltage regulator

is disabled.

Reading Serial Data

The filtered outputs of the input comparators are latched

into a shift register at the falling edge of CS. Clocking the

CLK pin, while CS is held low, shifts the latched data out

of SOUT 1 bit at a time.

The internal data serializer comprises a 16-bit shift register,

containing 8 bits of data corresponding to the eight field

inputs, as well as an 8-bit status byte containing supplementary

status and CRC information. The status byte contains 1 bit

representing the status of the field-supply voltage (UV),

1 bit representing the status of the internal temperature

monitor (OT), a 5-bit CRC code internally calculated and

generated, and a trailing 1 as a STOP bit.

The undervoltage (UV) bit is normally 0. If the supply

voltage falls below VOFFUVLO, the UV becomes a 1. The

UV bit returns to 0 once the supply voltage has returned

above VONUVLO.

Figure 1. Operation of Patent-Pending Switched Current Limiter

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

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DB1 DB0 BINARY VALUE DEBOUNCE TIME CURRENT SWITCHING PERIOD

0 0 0 0 DC (disabled)

0 1 1 25Fs 8Fs

1 0 2 0.75ms 0.25ms

1 1 3 3ms 1ms

24V

0V tDELAY tDELAY

100% ILIMIT

20% ILIMIT

TIME

INTERNAL FILTER CLOCK

COMPARATOR OUTPUT IS LATCHED INTO FILTER ON

RISING EDGE OF CLOCK

INPUT CURRENT LIMIT

SENSOR OUTPUT VOLTAGE

The overtemperature (OT) bit is also normally 0. If the

junction temperature increases to above TALRM, the OT

bit becomes a 1. The bit returns to 0 once the junction

temperature has returned below TALRM.

The CRC code can be used to check data integrity during

transfer from the device to an external microcontroller. In

applications where the integrity of data transferred is not

of concern, the CRC bits can be ignored. The CRC uses

the following polynomial:

P(x) = x5 + x4 + x2 + x0

The number of bits in the internal serializer can be select-

ed between 8 bits or 16 bits. The MODESEL pin is used

to configure the serializer as an 8-bit (disabling the status

byte) or 16-bit shift register. In 8-bit mode, only the eight

field input states are transferred through the SPI port and

the status byte is ignored. Therefore, in multiple IC appli-

cations (input channels greater than 8), if desired, only a

single status byte can be generated and transmitted for

any number of input channels.

The shift register contents are read only (no write capa-

bility exists) through the SPI-compatible interface.

For higher input counts than 8, multiple devices can

be cascaded. In this case, the SOUT pin of one

device should be connected to the SIN pin of the

next device, effectively cascading the internal shift

registers. The CLK and CS pins of all the devices should be

connected together in this configuration. See the Serial-

Port Operation section for more detailed information on

operating the SPI interface.

Temperature Monitoring

The internal junction temperature of the device is con-

stantly monitored. An alarm is raised, by asserting the

FAULT pin, if the temperature rises above TALRM. In

addition to asserting FAULT, the device sets the OT bit

to a 1.

Supply Voltage Monitoring

A supply voltage monitor circuit constantly monitors

the field-supply voltage. If this voltage falls below a

threshold (VOFFUVLO), an alarm is raised by asserting

the FAULT pin, indicating that the part is experiencing

a fault condition and the data in the serializer is not to

be trusted. In addition, the device sets the UV bit to a 1.

Once the field-supply voltage has recovered and goes

above VONUVLO, the FAULT pin is released, indicating

normal operation of the part.

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

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Figure 2. Basic Application Powered Through 5VOUT

MAX31910

RT1-8

RIREFGND

DB0

DB1

MODESEL

SIN

CLK

SOUT

FIN1-8 IN1-8

VCC24V 5VOUT

JUMPERS TO

5V AND GND

RINX

RREF

NOT

CONNECTED

FAULT

Note: For higher EFT performance, a minimum 1nF, 1000V capacitor can be added from nodes fIN1–fIN8 to earth or ground. For

additional methods to improve EFT robustness, please check the Maxim website regularly for upcoming application notes currently

being developed.

Applications Information

EMC Standards Compliance

The external components shown in Figure 3 allow the

device to operate in harsh industrial environments.

Components were chosen to assist in suppression of

voltage burst and surge transients, allowing the system

to meet or exceed international EMC requirements.

Table 2 lists an example device for each component

in Figure 3. The system shown in Figure 3, using the

components shown in Table 2, is designed to be robust

against IEC Fast Transient Burst, surge, conducted RFI

specifications, and ESD specifications (IEC 61000-4-2,

-4, -5, and -6).

Serial-Port Operation

Serial output of the device functions in one of two modes,

depending on the MODESEL setting (Table 3).

With MODESEL = 0, the device output includes a 5-bit

CRC, an undervoltage alarm, and an overtemperature

alarm. See the Detailed Description for CRC, undervolt-

age, and overtemperature functional descriptions.

With MODESEL = 1, the device outputs only the state

of the IN1–IN8 inputs and omits the CRC, undervoltage

alarm, and overtemperature alarm.

Daisy-Chain Operation

For systems with more than eight sensor inputs, multiple

devices can be daisy-chained to allow access to all data

inputs through a single serial port. When using a daisy-

chain configuration, connect SOUT of one of the devices

to the SIN input of another upstream device. CS and SCK

of all devices in the chain should be connected together

in parallel (see Figure 4).

In a daisy-chain configuration, external components

used to enhance EMC robustness do not need to be

duplicated for each device of a circuit board. Figure 5

illustrates a 16-input application.

SPI Waveforms

The serial output of the device adheres to the SPI proto-

col, running with CPHA = 0 and CPOL = 0. Input states

on IN1–IN8 are latched in on the falling edge of CS. The

transfer of data out of the slave output, SOUT, starts

immediately when CS is asserted (i.e., MSB is output

onto SOUT independent of CLK). The remaining data bits

are shifted out on the falling edge of CLK. The data bits

are written to the output SOUT with MSB first. When CS

is high, SOUT is high impedance. The resultant timing is

shown in Figure 6. Note that all bits after IN1 are invalid

if 8-bit operation mode is selected with the MODESEL

input. Figure 7, Figure 8, Figure 9, and Figure 10 illustrate

SPI timing specifications.

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

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COMPONENT DESCRIPTION REQUIRED/RECOMMENDED/OPTIONAL

C0 4.7nF, 2kV polypropylene capacitor Recommended

C1 10FF, 60V ceramic capacitor Required

C3 100nF, 10V ceramic capacitor Recommended

C4 4.7µF, 10V low ESR ceramic capacitor Required

C5 100nF, 100V ceramic capacitor Recommended

D0 36V fast zener diode (ZSMB36) Recommended

D1 General-purpose rectifier (IN4007) Optional: For reverse-polarity protection.

R1 150I, 1/3W MELF resistor Recommended

RINX 2.2kI, 1/4W MELF resistor Required

RREF 15kI, 1/8W resistor Required

Table 2. Recommended Circuit Components

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MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

Figure 3. Typical EMC Protection Circuitry

GND

MODESEL

DB1

DB0

5VOUT

SIN

CLK

SOUT

FAULT

CLK

SOUT

FAULT

ISOLATION

JUMPERS TO

5VOUT

AND GND

C4C3

VDD_LOGIC

RREF

RINX

fIN1–8

RIREF

IN1–8

RT1–8

VCC24V

MAX31910

24V

D0 C1

C0 C5

EARTH

FIELD

GROUND

Table 3. MODESEL Settings

Figure 4. Daisy-Chain Operation

MODESEL SETTING FUNCTIONALITY

016-bit output; [IN8–IN1][CRC (5 bit)][UV][OT][1]

18-bit output; [IN8–IN1]

MAX31910 MAX31910MAX31910

SIN

SOUT

SIN

SOUT

SIN

SOUT

TO µCONTROLLER

Figure 5. 16-Input Application Circuit

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│

MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

MODESEL

DB1

DB0

5VOUT

CLK

SOUT

FAULT

CLK

SOUT

FAULT

ISOLATION

SIN

JUMPERS TO

5VOUT

AND GND

JUMPERS TO

5VOUT

AND GND

C4C3

VDD_LOGIC

RREF

RINX

fIN1–8

RIREF GND

IN1–8

RT1–8

VCC24V

MAX31910

24V

D0 C1

EARTH

GND

FAULT

SOUT

CLK

SIN

MODESEL

DB1

DB0

5VOUT

RREF

RINX

fIN1–8

RIREF

IN1–8

RT1–8

VCC24V

MAX31910

Figure 6. SPI Communication Example

Figure 7. SPI Timing Diagram 1

Figure 8. SPI Timing Diagram 2

Figure 9. SPI Timing Diagram 3

Figure 10. SPI Timing Diagram 4

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│

MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

CLK

SOUT

IN8 –IN1

IN8 IN7 IN6 IN5 IN4 IN3 IN2 IN1 CRC4 CRC3 CRC2 CRC1 CRC0 UV OT 1

VALID

SOUT

tCSPW tP2

CS CLK

SIN

tSU1 tH1

SIN VALID

CLK

tSU2 tREC

tCSPW

1/fCLK

tR/F

tP1

SOUT

Ordering Information

+Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

Chip Information

PROCESS: S45JRS

Package Information

For the latest package outline information and land patterns

(footprints), go to www.maximintegrated.com/packages. Note

that a “+”, “#”, or “-” in the package code indicates RoHS status

only. Package drawings may show a different suffix character,

but the drawing pertains to the package regardless of RoHS status.

www.maximintegrated.com Maxim Integrated

│

MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

PART TEMP RANGE PIN-

PACKAGE CARRIER

MAX31910AUI+ -40NC to +125NC28 TSSOP Bulk

MAX31910AUI+T -40NC to +125NC28 TSSOP Tape

and Reel

PACKAGE

TYPE

PACKAGE

CODE

OUTLINE

NO.

LAND

PATTERN NO.

28 TSSOP-EP U28E+4 21-0108 90-0146

Revision History

Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses

are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)

shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

│

MAX31910 Ultra-Low Power Industrial, Octal, Digital Input

Translator/Serializer

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

0 8/12 Initial release —

1 9/12

Changed the supply voltage minimum from 10V to 7V; changed the current

limits in the EC table Note 5; added a new Figure 1 to show current-limit

switching; added the CRC polynomial to the Reading Serial Data section

1-4, 9

2 11/13

Updated Block Diagram, TOCs 4, 5, 8–10, Input Current Clamp, Low-Power

Current Clamp Switching, Basic Application Circuit, and EMC Standards

Compliance sections, Table 2, and Figures 2, 4, and 5

1, 5, 6, 8, 10–13

3 7/14 Added Note 11 to DC Electrical Characteristics table, deleted portion of

Table 2 note. 3, 4, 11

4 2/15 Updated front page content 1

5 4/15 Correct errata in General Description, added powering from 5VOUT,

corrected errata in figures, errata in Electrical Characteristics table.

1, 3, 5, 8, 10,

12-13, 15

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.

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MAX31910AUI+ MAX31910AUI+T