DESCRIPTION
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.

FEATURES
■ Two 8-Bit Current DACs
■ DACs Guaranteed Monotonic
■ Known IC State on Power-Up
■ Serial Interface Watchdog Timer with Disable
■ 2-Wire Serial Interface Compatible with I2C™and SMBus
■ 2 Programmable Fan Tachometer Interfaces
■ 4 Programmable General Purpose I/Os
■ Small 16-Pin SSOP Package
■ Single 2.7V to 5.75V Supply Operation
■ Fault Output Signal
■ Status Register
■ Fan Blasting Function
■ Nine Addresses Using Two Programming Lines