MIC3203 데이터 시트보기 (PDF) - Micrel

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MIC3203

High-Brightness LED Driver Controller with High-Side Current Sense

Micrel 

Micrel, Inc.

Functional Diagram

MIC3203

Figure 1. MIC3203/MIC3203-1 Block Diagram

Functional Description

The MIC3203 is a hysteretic step-down driver which

regulates the LED current over wide input voltage range.

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 reaches

4.5V, the internal 5V VCC is regulated and the DRV pin

is pulled high to turn on an external MOSFET if EN pin

and DIM pin are high. The inductor current builds up

linearly. When the CS pin voltage hits the VCS(MAX) with

respect to VIN, the MOSFET turns off and the Schottky

diode takes over and returns the current to VIN. Then the

current through inductor and LEDs starts decreasing.

When CS pin hits VCS(MIN), 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

calculation for frequency of operation is given in application

section.

The MIC3203 has an on board 5V regulator which is for

internal use only. Connect a 1µF capacitor on VCC pin to

analog ground.

The MIC3203 has an EN pin which gives the flexibility to

enable and disable the output with logic high and low

signals.

The MIC3203 also has a DIM pin which can turn on and off

the LEDs if EN is in HIGH state. This DIM pin controls the

brightness of the LED by varying the duty cycle of DIM pin

from 1% to 99%.

March 2010

10

M9999-032910-A

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