LT1786F Datasheet | Linear Technology

LT1786F SMBus Programmable CCFL Switching Regulator Features s s s s s s s Wide Battery Input Range: 4.5V to 30V Grounded Lamp or Floating Lamp Configurations Open Lamp Protection Precision 100µA Full-Scale DAC Programming Current 2-Wire SMBus Interface Two Selectable SMBus Addresses DAC Setting Is Retained in Shutdown to-lamp-current control” and municates using the 2-wire SMBus serial interface. The LT1786F acts as an SMBus slave device using one of two selectable SMBus addresses set by the address pin ADR. On Power-up, the DAC output current assumes midrange or zero scale, depending on the logic state of the ADR pin.The entire IC can be shut down through the SMBSUS pin or by setting the SHDN bit = 1 in the SMBus mand byte. Digital data for the DAC output current is retained internally and the supply current drops to 40µA for standby operation. The active low SHDN pin disables the CCFL control circuitry, but keeps the DAC alive. Supply current in this operating mode drops to 150µA. The LT1786F control circuitry operates from a logic supply voltage of 3.3V or 5V. The IC also has a battery supply pin that operates from 4.5V to 30V. The LT1786F draws 6m A typical quiescent current. A 200k Hz switching frequency minimizes magnetic ponent size. Current mode switching techniques with cycle-by-cycle limiting gives high reliability and simple loop frequency pensation. The LT1786F is available in a 16-pin narrow SO package. , LTC and LT are registered trademarks of Linear Technology Corporation. U APPLICATIONS s s s Notebook and Palmtop puters Portable Instruments Personal Digital Assistants DESCRIPTION The LT ®1786F is a fixed frequency, current mode, switching regulator that provides the control function for Cold Cathode Fluorescent Lighting (CCFL). The IC includes an efficient high current switch, an oscillator, output drive logic, control circuitry and a micropower 6-bit 100µA fullscale current output DAC. The DAC provides simple “bits- TYPICAL...