LM3402/02HV switching regulator has the following characteristics: input voltage range? 6V ~ 75V, using the circuit layout of buck regulator; It can provide constant driving current for light-emitting diodes, and the feedback voltage is 200mV；; When the RON pin is at low potential, the turn-off current will be further reduced; Accurate PWM brightness control; Switching frequency is as high as1MHz; It has hysteresis function and fixed conduction time. Therefore, switching frequency (FSW) control can be performed in the entire input voltage range.
The LM3402/02HV switching regulator in the figure is equipped with a dedicated DIM pin, which can accurately control the brightness by using linear and PWM input signals. Generally, the lighting system using light-emitting diodes uses PWM light and shade control to control the brightness of lights, which has become a widely adopted standard in the industry. As long as the current of the forward LED is adjusted, the light output of the LED will increase or decrease linearly, but most of the light bands will shift. Some applications are not very strict about color, so linear brightness control mode will still be adopted. However, brake lights, LCD backlights, direct display RGB light-emitting diodes and other automobile lights have very strict requirements on brightness and color, so this kind of application generally adopts PWM to control brightness.
Application Diagram of LM3402/02HV Switching Regulator