Analog Devices Inc./Maxim Integrated

The MAX31725/MAX31726 temperature sensors accurately measure temperature and provide an overtemperature alarm/interrupt/shutdown output. These devices convert the temperature measurements to digital form using a high-resolution, sigma-delta, analog-to-digital converter (ADC). Accuracy is ±0.5°C from -40°C to +105°C. Communication is through an I2C-compatible 2-wire serial interface.The I2C serial interface accepts standard write byte, read byte, send byte, and receive byte commands to read the temperature data and configure the behavior of the open-drain overtemperature shutdown output.The MAX31725 features three address select lines with a total of 32 available addresses. The MAX31726 features two address select lines with a total of 16 available addresses and an active-low RESET input. The sensors have a 2.5V to 3.7V supply voltage range, low 600µA supply current, and a lockup-protected I2C-compatible interface that make them ideal for a wide range of applications, including PCs, electronic test equipment, and office electronics.Both devices are available in an 8-pin TDFN package and operate over the -55°C to +150°C temperature range.ApplicationsIndustrialNetworkingServersTelecom

The MAX31732 is a multi-channel temperature sensor that monitors its own temperature and the temperatures of up to four external diode-connected transistors. A resistance cancellation feature compensates for up to 300Ω of series resistance between the external thermal diode and the MAX31732, while beta compensation corrects for temperature-measurement errors due to low-beta sensing transistors. The sensor also allows ideality factors between 0.9844 and 1.311.The MAX31732 offers two open-drain, active-low alarm outputs,ALARM1andALARM2. When the measured temperature of a channel crosses the respective primary overtemperature/undertemperature threshold levels,ALARM1asserts low, and a status bit is set in the corresponding thermal status registers. When the measured temperature of a channel crosses the secondary overtemperature/undertemperature threshold levels,ALARM2asserts low and a status bit is set in the corresponding thermal status registers. The highest temperature register allows the controller to obtain the temperature of the hottest channel.A 512-bit nonvolatile memory (NVM) allows the MAX31732 to program the configuration registers during power-up without software/firmware intervention. The NVM also captures the fault temperature for each remote and local channel for further analysis at a later time.The 2-wire serial interface accepts SMBus protocols (write byte, read byte, send byte, and receive byte) for reading the temperature data and programming the temperature thresholds. Any one of the eight available target addresses can be selected using the address selection input (ADD), which can be connected to ground or connected to a grounded resistor.The is specified over the -40°C to +125°C operating temperature range and with a 3.0V to 3.6V input supply range. MAX31732 is available in a 24-pin, 4mm x 4mm TQFN package.APPLICATIONSTemperature Measurement of On-Chip CPU, ASIC, SOC, or FPGA diodes or remote discrete diodesIndustrial-Thermal Management

The MAX31740 is a sophisticated, yet easy-to-use fan-speed controller. It monitors the temperature of an external NTC thermistor and generates a PWM signal that can be used to control the speed of a 2-, 3-, or 4-wire fan. The fan control characteristics are set using external resistors, thereby eliminating the need for an external microcontroller. Controllable characteristics include the starting temperature for fan control, PWM frequency, fan speed at low temperatures, and slope of the temperature-duty-cycle transfer function.Because the operating characteristics are selected by hardwired passive components, a simple, low-cost fan-speed controller can be implemented without the need for firmware development. This can dramatically reduce development time for the fan control function.The MAX31740 is available in a 2mm x 3mm, 8-pin TDFN package.ApplicationsCommunications EquipmentComputing EquipmentConsumer EquipmentIndustrial Equipment

The MAX31760 integrates temperature sensing along with precision PWM fan control. It accurately measures its local die temperature and the remote temperature of a discrete diode-connected transistor, such as a 2N3906, or a thermal diode commonly found on CPUs, graphics processor units (GPUs), and other ASICs. Multiple temperature thresholds, such as local high/overtemperature (OT) and remote high/overtemperature, can be set by an I2C-compatible interface.Fan speed is controlled based on the temperature reading as an index to a 48-byte lookup table (LUT) containing user-programmed PWM values. The flexible LUT-based architecture enables the user to program a smooth nonlinear fan speed vs. temperature transfer function to minimize acoustic fan noise. Two tachometer inputs allow measuring the speeds of two fans independently. The active-low FF/FS pin multiplexes an open-drain fan-failure output with a full-speed fan-drive input. When the local or remote OT threshold is exceeded, the active-low SHDN pin is asserted low and can be used to shut down the system. A dedicated active-low ALERT pin reports that either a local or remote high-temperature threshold has been exceeded. Active-low ALERT can be programmed to work in either fault indicator mode or interrupt mode. These features make the device a compact and complete solution for a single-fan or two-fan cooling system.ApplicationsNAS/DASNetworking EquipmentServersSTB/DVR