MAX31820 1-Wire Ambient Temperature Sensor General Description Benefits and Features The MAX31820 ambient temperature sensor provides Uniq ue 1-Wire Interface Requires Only One Port Pin 9-bit to 12-bit Celsius temperature measurements with for Communication 0.5C accuracy over a +10C to +45C temperature Each Device has a Unique 64-Bit Serial Code Stored range. Over its entire -55C to +125C operating range, in On-Board ROM the device has 2.0C accuracy. Multidrop Capability Simplifies Distributed The device communicates over a 1-Wire bus that, by Temperature-Sensing Applicati ons definition, requires only one data line (and ground) for Requ ires No External Components communication with a central microprocessor. In addition, the device can derive power directly from the data line Can Be Powered from Data Line 3.0V to 3.7V (parasite power), eliminating the need for an external Power-Supply Range power supply. Requiring so few pins enables the device Measures Temperatures from -55C to +125C (-67F to be placed in a 3-pin TO-92 package. The form factor to +257F) of this package allows the device to be placed above 0.5C Accuracy from +10C to +45C the board and thus measure the ambient temperature of a system, as opposed to the board temperature that a Thermometer Resolution is User-Selectable from surface-mount package would measure. 9 Bits to 12 Bits Each MAX31820 has a unique 64-bit serial code, which Converts Temperature to 12-Bit Digital Word in allows multiple MAX31820 devices to function on the same 750ms (Max) 1-Wire bus. Therefore, it is simple to use one microproces- User-Definable Nonvolatile (NV) Alarm Settings sor to control many devices distributed over a large area. Alarm Search Command Identifies and Addresses Applications Devices Whose Temperature is Outside Programmed Limits (Temperature Alarm Condition) HVAC Environmental Contr ols Temperature Monitoring Sy stems Inside Buildings, Available in 3-Pin TO-92 Package Equipment, or Machinery TO-92 Package Allows Measurement of Ambient Process Monitoring and Co ntrol Systems Temperature Thermostatic Controls Software Compatible with the DS1822 and DS18B20 Industrial Systems Consumer Products Ordering Information appears at end of data sheet. Thermometers Any Thermally Sensitive Sy stem For related parts and recommended products to use with this part, refer to www.maximintegrated.com/MAX31820.related. Block Diagram V PU 4.7k MEMORY CONTROL LOGIC DQ MAX31820 PARASITE- POWER CIRCUIT TEMPERATURE REGISTER 64-BIT ROM GND AND ALARM HIGH TRIGGER 1-Wire PORT (T ) REGISTER (EEPROM) H C PP SCRATCHPAD ALARM LOW TRIGGER (T ) REGISTER (EEPROM) L POWER- CONFIGURATION REGISTER (EEPROM) V SUPPLY DD SENSE 8-BIT CRC GENERATOR 1-Wire is a registered trademark of Maxim Integrated Products, Inc. 19-6731 Rev 0 6/13MAX31820 1-Wire Ambient Temperature Sensor Absolute Maximum Ratings Voltage Range on Any Pin Relative to Ground .... -0.5V to +6.0V Storage Tempera ture Range ............................ -55C to +125C Operating Temperature Range ......................... -55C to +125C Soldering Temperature (reflow) .......................................+260C 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. DC Electrical Characteristics (V = 3.0V to 3.7V, T = -55C to +125C, unless otherwise noted.) (Note 1) DD A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage V Local power (Note 2) +3.0 +3.7 V DD Parasite power +3.0 +3.7 Pullup Supply Voltage V V PU (Notes 2, 3) Local power +3.0 V DD +10C to +45C 0.5 Thermometer Error (Note 4) T C ERR -55C to +125C 2 Input Logic-Low V (Notes 2, 5, 6) -0.3 +0.8 V IL lower of 3.7 Local power +2.2 or (V + DD 0.3) Input Logic-High (Notes 2, 7) V V IH lower of 3.7 Parasite power +3.0 or (V + DD 0.3) Sink Current I V = 0.4V (Note 2) 4.0 mA L I/O Standby Current I (Notes 8, 9) 750 1000 nA DDS Active Current I V = 5V (Note 10) 1 1.5 mA DD DD DQ Input Current I (Note 11) 5 A DQ Drift (Note 12) 0.2 C Maxim Integrated 2 www.maximintegrated.com