Remote Temperature Sensor with SMBus Serial Interface

The MAX1618 precise digital thermometer reports the temperature of a remote sensor. The remote sensor is a diode-connected transistor-typically a low-cost, easily mounted 2N3904 NPN type-that replaces conventional thermistors or thermocouples. Remote accuracy is ±3°C for multiple transistor manufacturers, with no calibration needed. The MAX1618 can also measure the die temperature of other ICs, such as microprocessors, that contain an on-chip, diode-connected transistor.

The 2-wire serial interface accepts standard System Management Bus (SMBus™) Write Byte, Read Byte, Send Byte, and Receive Byte commands to program the alarm thresholds and to read temperature data. The data format is 7 bits plus sign, with each bit corresponding to 1°C, in two's complement format. Measurements can be done automatically and autonomously, with the 16Hz conversion rate or programmed to operate in a single-shot mode.

The thermostat mode configures the active-low ALERT output as an interrupt or as a temperature reset that remains active only while the temperature is above the maximum temperature limit or below the minimum temperature limit. The active-low ALERT output polarity in thermostat mode can be configured for active high or active low. Fan control is implemented using this active-low ALERT output.

The MAX1618 is available in a small (1.1mm high) 10-pin µMAX package.

Applications

* Central Office Telecom Equipment * Computers: Desktop, Workstation, Server * Industrial Controls * LAN Servers * Multichip Modules * Smart Battery Packs/Chargers * Test and Measurement Equipment

* Single Channel: Measures Remote CPU Temperature

* No Calibration Required

* SMBus 2-Wire Serial Interface

* Programmable Under/Overtemperature Alarms

* Overtemperature Output for Fan Control (Thermostat Mode)

* Supports SMBus Alert Response Accuracy

* ±3°C (+60°C to +100°C)

* ±5°C (-55°C to +120°C)

* 3°A (typ) Standby Supply Current

* 900°A (max) Supply Current in Autoconvert Mode

* +3V to +5.5V Supply Range

* Small 10-Pin °MAX Package