The LM3404 is a "Constant Current Buck Regulator for Driving High Power LEDs." One of the features the datasheet boasts is "LED dimming using pulse width modulation (PWM)." My question is, using this chip (and its associated support ciruitry), which of the following accurately reflects the nature of the current delivered to the LEDs?
- the LEDs are actually switched on and off (chopped current) at the configured constant current in relation to the PWM input signal
- the LED current is proportionately (i.e. in accordance with PWM duty cycle) reduced from the nominal fully bright constant current, but still driven by constant current (i.e. unmodulated).
- Something else, if so please explain