MAX31820
1-Wire Ambient Temperature Sensor
General Description
The MAX31820 ambient temperature sensor provides
9-bit to 12-bit Celsius temperature measurements with
±0.5°C accuracy over a +10°C to +45°C temperature
range. Over its entire -55°C to +125°C operating range,
the device has ±2.0°C accuracy.
The device communicates over a 1-Wire® bus that, by
definition, requires only one data line (and ground) for
communication with a central microprocessor. In addition,
the device can derive power directly from the data line
(“parasite power”), eliminating the need for an external
power supply. Requiring so few pins enables the device
to be placed in a 3-pin TO-92 package. The form factor
of this package allows the device to be placed above
the board and thus measure the ambient temperature of
a system, as opposed to the board temperature that a
surface-mount package would measure.
Each MAX31820 has a unique 64-bit serial code, which
allows multiple MAX31820 devices to function on the same
1-Wire bus. Therefore, it is simple to use one microproces-
sor to control many devices distributed over a large area.
Applications
● HVAC Environmental Controls
● Temperature Monitoring Systems Inside Buildings,
Equipment, or Machinery
● Process Monitoring and Control Systems
● Thermostatic Controls
● Industrial Systems
● Consumer Products
● Thermometers
● Any Thermally Sensitive System
Block Diagram
VPU
4.7kΩ
DQ
PARASITE-
POWER
CIRCUIT
64-BIT ROM
GND AND
CPP 1-Wire PORT
POWER-
VDD SUPPLY
SENSE
Benefits and Features
● Unique 1-Wire Interface Requires Only One Port Pin
for Communication
● Each Device has a Unique 64-Bit Serial Code Stored
in On-Board ROM
● Multidrop Capability Simplifies Distributed
Temperature-Sensing Applications
● Requires No External Components
● Can Be Powered from Data Line; 3.0V to 3.7V
Power-Supply Range
● Measures Temperatures from -55°C to +125°C (-67°F
to +257°F)
● ±0.5°C Accuracy from +10°C to +45°C
● Thermometer Resolution is User-Selectable from
9 Bits to 12 Bits
● Converts Temperature to 12-Bit Digital Word in
750ms (Max)
● User-Definable Nonvolatile (NV) Alarm Settings
● Alarm Search Command Identifies and Addresses
Devices Whose Temperature is Outside Programmed
Limits (Temperature Alarm Condition)
● Available in 3-Pin TO-92 Package
● TO-92 Package Allows Measurement of Ambient
Temperature
● Software Compatible with the DS1822 and DS18B20
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part, refer
to www.maximintegrated.com/MAX31820.related.
MEMORY
CONTROL LOGIC
SCRATCHPAD
MAX31820
TEMPERATURE REGISTER
ALARM HIGH TRIGGER
(TH) REGISTER (EEPROM)
ALARM LOW TRIGGER
(TL) REGISTER (EEPROM)
CONFIGURATION REGISTER (EEPROM)
8-BIT CRC GENERATOR
1-Wire is a registered trademark of Maxim Integrated Products, Inc.
19-6731; Rev 0; 6/13
