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. Field-side LED drivers recycle
the current from the eight inputs to provide visual input
status indication without any additional current or power
consumption.
The MAX31912 uses patent-pending circuit techniques
to achieve further reduction of power beyond what is
possible by input current limiting alone.
For low-cost applications, Maxim Integrated offers a pin-
compatible version of this device, the MAX31913, which
does not include the patent-pending current-switching
circuitry included in the MAX31912.
Benefits and Features
●
Ultra-Low Power and Heat Dissipation
• Low Quiescent Current (1.6mA, 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
• Energy-Less Field-Side LED Drivers
●
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
• Dual On-Chip Field Supply Voltage Monitors
• 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
Ordering Information
appears at end of data sheet.
19-6925; Rev 3; 4/15
MAX31912
Ultra-Low Power Industrial, Octal,
Digital Input Translator/Serializer
Block Diagram
24V
V
CC24V
5V REGULATOR
SUPPLY
MONITOR
TEMP
MONITOR
RIREF
RT1
IN1
SENSORS
VREF
VOLTAGE
COMPARATOR
INPUT CHANNEL 0
SERIALIZER
VREF
5VOUT
5V
MAX31912
FAULTB
DB0
DB1
CRC GEN.
LP
FILTER
SIN
MODESEL
CLK
CS
µCONTROLLER
OR
ISOLATION
SWITCHED
CURRENT
LIMITER
RT8
IN8
GND
INPUT CHANNEL 7
SOUT
MAX31912
Ultra-Low Power Industrial, Octal,
Digital Input Translator/Serializer
Absolute Maximum Ratings
(Voltages relative to GND.)
Voltage Range on V
CC24V
....................................-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 (V
5VOUT
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
TSSOP (derate 27mW/°C above +70°C)
...............2162.2mW
Operating Temperature Range
Ambient Temperature .....................................
-40°C to +125°C
Junction Temperature .....................................
-40°C to +150°C
Storage Temperature Range ............................
-55°C to +125°C
Lead Temperature (soldering, 10s) ................................. +300°C
Soldering Temperature (reflow) .......................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation 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)
TSSOP
Junction-to-Ambient Thermal Resistance (θ
JA
)...........37°C/W
Junction-to-Case Thermal Resistance (θ
JC
)..................2°C/W
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.
Recommended Operating Conditions (Note 2)
PARAMETER
Field Supply Voltage
Field Inputs Voltage
Logic Inputs Voltage
Current-Limit Setting Resistor
Field Input Data Rate
SYMBOL
V
CC24V
V
INn
V
LOGIC
R
REF
f
IN
(Note 5)
(Note 3)
(Note 4)
CONDITIONS
MIN
7
-0.3
0
15
200
TYP
MAX
36
36
5.5
UNITS
V
V
V
kΩ
kHz
www.maximintegrated.com
Maxim Integrated
│
3
MAX31912
Ultra-Low Power Industrial, Octal,
Digital Input Translator/Serializer
DC Electrical Characteristics
(V
CC24V
= 7V to 36V, T
J
= -40°C to +150°C, unless otherwise noted.) (Note 2)
PARAMETER
Field-Supply Current
Field-Supply UV1 Alarm Off/On
Field-Supply UV1 Alarm On/Off
Field-Supply UV2 Alarm Off/On
Field-Supply UV2 Alarm On/Off
LED On-State Current
Field Input Threshold High-to-
Low
Field Input Threshold Low-to-
High
Field Input Hysteresis
Input Threshold High-to-Low
(at IC pin)
Input Threshold Low-to-High
(at IC pin)
Input Threshold Hysteresis
(at IC pin)
Field Input Pin Resistance
Field Input Current Limit
SYMBOL
I
CC24V
V
ONUV1
V
OFFUV1
V
ONUV2
V
OFFUV2
I
RT-ON
V
IN-(INF)
V
IN+(INF)
V
HYS(INF)
V
TH-(INP)
V
TH+(INP)
V
HYS(INP)
R
INP
I
INLIM
R
REF
= 15kΩ, V
CC24V
= 18V to 30V,
T
A
= +25°C to +125°C (Note 6)
DB1/DB0 = 0/0: no filtering
Filter Time Constant
t
FILTER
DB1/DB0 = 0/1
DB1/DB0 = 1/0
DB1/DB0 = 1/1
Linear Regulator Output
Regulator Line Regulation
Regulator Load Regulation
Logic-Low Output Voltage
Logic-High Output Voltage
Logic-Input Trip Point
Logic-Input Leakage Current
Overtemperature Alarm
V
5VOUT
dVREG
LINE
dVREG
LOAD
V
OL
V
OH
V
IH-IL
I
IL
T
ALRM
Max I
LOAD
= 50mA
I
LOAD
= 50mA
I
LOAD
= 1mA to 50mA
I
OL
= 4mA
I
OH
= -4mA
4.0
0.3 x
V
5VOUT
-50
0.5 x
V
5VOUT
-30
135
0.7 x
V
5VOUT
-15
0.008
0.25
1.0
4.75
2.2
(Note 12)
(Note 12)
R
REF
= 15kΩ, V
CC24V
= 18V to 30V
2.2kΩ external series resistor
2.2kΩ external series resistor
(Note 12)
2.2kΩ external series resistor
(Note 12)
3
7
14
7
CONDITIONS
IN1–IN8 = 24V, 5VOUT = open,
RT1–RT8 = GND, all logic inputs open
MIN
TYP
1.6
9
8
16.5
15.5
2.2
8.4
9.4
1
3.4
4.4
1
0.8
2.4
0
0.025
0.75
3
5.0
10
20
0.4
1.0
0.038
1.1
4.5
5.25
V
mV
mV
V
V
V
µA
°C
ms
2.7
5
10.2
18
MAX
2.3
10
UNITS
mA
V
V
V
V
mA
V
V
V
V
V
V
kΩ
mA
www.maximintegrated.com
Maxim Integrated
│ 4
MAX31912
Ultra-Low Power Industrial, Octal,
Digital Input Translator/Serializer
AC Electrical Characteristics
(V
CC24V
= 7V to 36V, T
J
= -40°C to +150°C, unless otherwise noted.) (Note 2)
PARAMETER
Field Input Pulse Width
ESD
SYMBOL
t
PW
CONDITIONS
No external capacitors on pins
IN1-IN8
HBM, all pins
HBM, IN1-IN8 with respect to GND
MIN
1
±2
±15
TYP
MAX
UNITS
µs
kV
AC Electrical Characteristics: SPI Interface
(V
CC24V
= 7V to 36V, T
J
= -40°C to +150°C, unless otherwise noted.) (Note 2)
PARAMETER
CLK Pulse Duration
CS
Pulse Duration
SIN to CLK Setup Time
SIN to CLK Hold Time
CS
to CLK Setup Time
CS
to CLK Recovery Time
Clock Pulse Frequency
Propagation Delay, CLK to SOUT
Propagation Delay,
CS
to SOUT
Rise/Fall Time SOUT/FAULT
Note 2:
SYMBOL
t
CLKPW
t
CSPW
t
SU1
t
H1
t
SU2
t
REC
f
CLK
t
P1
t
P2
t
R/F
(Note 7)
(Note 8)
(Note 9)
(Note 9)
(Note 10)
(Note 10)
(Notes 7, 11)
(Note 7)
(Note 8)
(Note 7)
CONDITIONS
MIN
20
20
5
8
8
12
25
20
20
40
TYP
MAX
UNITS
ns
ns
ns
ns
ns
ns
MHz
ns
ns
ns
Limits are 100% production tested at T
A
= +25°C and T
A
= +125°C. Limits over the operating temperature range and rel-
evant supply voltage range are guaranteed by design and characterization. Typical values are not guaranteed.
Note 3:
If a 24V supply is not available, the device can be powered through V
5VOUT
. In this mode of operation, the V
CC24V
sup-
ply must be left unconnected. All other specifications remain identical. The field-supply UV1 and UV2 alarms will be acti-
vated (set to 1), indicating the absence of the 24V supply in this mode of operation.
Note 4:
When using suggested external 2.2kΩ series resistors, limits of -3V to +36V apply.
Note 5:
f
IN
refers to the maximum pulse frequency (1/fIN = shortest pulse width) that can be detected from the field sensors and
switches.
Note 6:
External resistor R
REF
can be adjusted to set any desired current limit between 0.5mA and 6mA.
Note 7:
See Figure 9.
Note 8:
See Figure 6.
Note 9:
See Figure 8.
Note 10:
See Figure 7.
Note 11:
This is the maximum bit transfer rate through the serializer interface.
Note 12:
When input current switching is enabled (DB0/DB1 /= 00), there is no Input Threshold Hysteresis. In this case, the Input
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