HM2802 datasheet(9/12 Pages) HMSEMI

9 / 12 page

30V 1.5A 1MHz Sync Step-Down Dimmable LED Driver

Applications Information

Setting the LED Current

The LED current is controlled by the feedback resistor, RS1, in the following table. The current through the LEDs is

given by the equation 100mV/RS1. Following table shows the selection of resistors for a given LED current.

ILED (A)

R1 (Ω)

1.5

0.067

0.1

RS1=0.1 / ILED

ILED is average LED current.

Analog/PWM Dimming Control

1.Using a PWM Signal to DIM Pin

For controlling the LED brightness, the HM2802 can perform the dimming control by applying a PWM signal to

DIM pin. The internal soft start and the wide range dimming frequency can eliminate inrush current and audio noise

when dimming. The average LED current is proportional to the PWM signal duty cycle. The magnitude of the PWM

signal should be higher than the minimum enable voltage of DIM pin, in order to let the dimming control, perform

correctly, a 3V<= DIM <=VIN voltage is recommended.

2.Using a DC Voltage

When the VIN remains at a normal operating voltage, we can add a 0.65V to 1.2V DC voltage at the DIM Pin to

adjust the brightness of the LED lamp group.

DIM

RDM1 10KΩ

RDIM2

1MΩ

CDIM1

0.1μF

Dimming

Signal

0.65V to 1.2V

When the applied voltage signal increases linearly in the range of 0.65V to 1.2V, the current passing through the

LED will increase linearly and reach the set maximum (VFB/RS1) value around 1.2V, as shown in the following

graph. When the applied voltage exceeds 1.2V, the LED current will no longer increase linearly.

HM2802 Datasheet(PDF) 9 Page - Shenzhen Huazhimei Semiconductor Co., Ltd