Created: May 18, 2017
No description available.
This reference design features a hysteretic, step-down, constant-current driver for high-brightness LEDs. The MAQ3203 is ideal for lighting applications with wide operating voltage range. It can operate from 4.5V up to 42V. The device has 90% efficiency with ±5% LED current accuracy. It can operate up to 1.5MHz switching frequency which allows the use of smaller external components minimizing space and cost.
As shown in the circuit, the MAQ3203 device have an enable (EN) and dimming (DIM) input pins. These pins must be pulled to HIGH but not above the input supply voltage in order for the device to operate and the output to be enabled. The device operates from a 4.5V to 42V input MOSFET voltage range and provides up to 0.5A source and 1A sink drive capability. When the input voltage at the VIN pin reaches 4.5V, the internal 5V regulator regulates the voltage and the DRV pin is pulled HIGH to turn on the external MOSFET Q1. The inductor current builds up linearly. When the CS pin voltage hits the current sense upper threshold with respect to VIN, the MOSFET turns off and the Schottky diode D1 takes over and returns the current to VIN. Then the current through inductor and LEDs starts decreasing. When CS pin voltage hits current sense lower threshold, the MOSFET turns on and the cycle repeats. The frequency of operation depends upon input voltage, total LEDs voltage drop, LED current, and temperature.
The enable (EN) and PWM dimming (DIM) pins are connected to header J1. The EN pin enables or disables the device through a HIGH or LOW signal. The DIM pin provides control of the LED brightness. It can be used to vary the duty cycle of the output from 1% to 99%. The screw terminal ST1 can be used to connect the input supply voltage while ST2 can be used to connect the high-brightness LEDs. The MAQ3203 provides an ideal solution for interior/exterior lighting, architectural and ambient lighting, LED bulbs, and other general illumination applications. It can be also used for automotive and industrial lighting applications.