FAN-SPEED REGULATOR WITH 1°C REMOTE TEMPERATURE SENSOR PROVIDES AUTOMATIC CLOSED-LOOP FAN CONTROL AND KEEPS SYSTEMS QUIET
SUNNYVALE, CA-December 4, 2001-Maxim Integrated Products introduces the MAX6660 remote temperature sensor and intelligent closed-loop fan controller. Fan speed is voltage controlled, as opposed to PWM controlled, greatly reducing acoustic noise and maximizing fan reliability. An on-chip power device drives 5V and 12V fans rated up to 250mA.
Housed in a small 16-pin QSOP package, the MAX6660 measures the temperature of a common-collector PNP, such as a substrate PNP of a microprocessor, or a discrete diode-connected bipolar transistor. The MAX6660 uses this measurement to regulate the speed of the fan, freeing up the processor from fan control functions.
The closed-loop fan controller regulates fan speed with tachometer feedback from the fan. It compares temperature data to a fan threshold temperature and gain setting, both programmed over the SMBus™ by the user, and adjusts fan speed based on the remote-junction temperature. If desired, the automatic temperature-based fan speed control function can be bypassed and the fan can be placed under direct "open-loop" control.
Temperature data is updated every 0.25 seconds and is readable at any time over the SMBus interface. The MAX6660 is accurate to 1°C (max) when the remote junction is between +60°C and +100°C, and 3°C accurate (max) when the remote junction is between 25°C and +125°C. Data are formatted as an 11-bit word with 0.125°C resolution.
When a temperature or voltage measurement falls outside the user-programmed high and low limit thresholds, the MAX6660 generates a latched interrupt output at the ALERT pin. If desired, the interrupt can be masked out. In addition, the OVERT comparator output asserts when the temperature exceeds the programmed high limit and deasserts only when the temperature falls below the programmed low limit. This pin can be used to facilitate a system shutdown.
Communication is through a 2-wire serial interface accepting standard SMBus protocol. This interface is used to program the configuration of the MAX6660, including all temperature alarm thresholds, the fan trip threshold and gain settings. It is also used to directly set fan speed in open-loop mode.
The MAX6660 operates with a supply voltage between +3.0V and +5.5V. Average supply current is 250µA (typ) and standby current is just 3µA (typ).
Prices start at $3.19 (1000-up, FOB USA).
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