The LTC?3783 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.