Features

• True Color PWM Delivers Constant Color with 3000:1 Dimming Ratio
• Fully Integrated Load FET Driver for PWM Dimming Control of High Power LEDs
• 100:1 Dimming from Analog Inputs
• Wide FB Voltage Range: 0V to 1.23V
• Constant Current or Constant Voltage Regulation
• Low Shutdown Current: IQ = 20μA
• 1% 1.23V Internal Voltage Reference
• 2% RUN Pin Threshold with 100mV Hysteresis
• Programmable Operating Frequency (20kHz to  1MHz) with One External Resistor
• Synchronizable to an External Clock Up to 1.3fOSC
• Internal 7V Low Dropout Voltage Regulator
• Programmable Output Overvoltage Protection
• Programmable Soft-Start
• Can be Used in a No RSENSE Mode for VDS < 36V
• 16-Lead DFN and TSSOP Packages

Typical Application

Description

The LTC3783 is a current mode LED driver and boost, flyback and SEPIC controller that drives both an N-channel power MOSFET and an N-channel load PWM switch. When using an external load switch, the PWMIN input not only drives PWMOUT, but also enables controller GATE switching and error amplifier operation, allowing the controller to store load current information while PWMIN is low. This feature (patent pending) provides extremely fast, true PWM load switching with no transient overvoltage or undervoltage issues; LED dimming ratios of 3000:1 can be achieved digitally, avoiding the color shift normally associated with LED current dimming. The FBP pin allows analog dimming of load current, further increasing the effective dimming ratio by 100:1 over PWM alone.

In applications where output load current must be returned to VIN, optional constant current/constant voltage regulation controls either output (or input) current or output voltage and provides a limit for the other. ILIM provides a 10:1 analog dimming ratio.

For low- to medium-power applications, No RSENSE mode can utilize the power MOSFET’s on-resistance to eliminate the current-sense resistor, thereby maximizing efficiency. The IC’s operating frequency can be set with an external resistor over a 20kHz to 1MHz range and can be synchronized to an external clock using the SYNC pin.

The LTC3783 is available in the 16-lead DFN and TSSOP packages.