The SN3340 is a continuous mode inductive step-down converter, designed for driving single or multiple series connected LEDs efficiently from a voltage source higher
than the LED voltage. The device operates from an input
supply between 5V and 18V and provides an externally
adjustable output current of up to 350mA. Depending upon
supply voltage and external components, this can provide up to 10 watts of output power.
The SN3340 includes the output switch and a high-side
output current sensing circuit, which uses an external
resistor to set the nominal average output current.
Output current can be adjusted above, or below the set
value, by applying an external control signal to the ADJ pin.
The ADJ pin will accept either a DC voltage or a PWM
waveform. Depending upon the control frequency, this will
provide either a continuous or a gated output current. The
PWM filter components are contained within the chip.
The PWM filter provides a soft-start feature by controlling
the rise of input/output current. The soft-start time can be
increased using an external capacitor from the ADJ pin to ground.
Applying a voltage of 0.2V or lower to the ADJ pin turns the output off and switches the device into a low current standby state. The device is assembled in a TSOT23-5 package.