LTC1840

The LTC^®1840 is a fan controller with two 8-bit current output DACs, two tachometer interfaces, and four general purpose I/O (GPIO) pins.  It operates from a single supply with a range of 2.7V to 5.75V. A current output DAC is used to control an external switching regulator, which controls the fan speed. A current output DAC and tachometer allow a controller to form a closed control loop on fan velocity. The GPIO pins  can be used as digital inputs or open drain
pull-down outputs.

The part of LTC1840 features a simple 2-wire I²C and SMBus compat-ible serial interface that allows communication between many devices. The interface includes a fault status register that reflects the state of the part and which can be polled to find the cause of a fault condition. Other operational characteristics of the part, such as DAC output currents, GPIO modes, and tachometer frequency, are also pro-grammed through the serial interface. Two address pins provide nine possible device addresses.

The BLAST</a>pin of LTC1840 is provided to force the DAC output currents to program the maximum regulator output voltages through a single pin and gate the operation of the serial access timer.