MIC3201_11 Datasheet, PDF (8/16 Pages) Micrel Semiconductor – High Brightness LED Driver with High-Side Current Sense

Micrel, Inc.
Functional Diagram
MIC3201
Figure 1. MIC3201 Block Diagram
Functional Description
The MIC3201 is a hysteretic step-down regulator which
regulates the LED current over wide input voltage range
and capable of driving up to four, 1A LEDs in series.
The device operates from a 6V to 20V input voltage range,
and includes an integrated 1.0A power switch. When the
input voltage approaches 6V, the internal 5V VCC is
regulated and the integrated MOSFET is turned on if EN
pin and DIM pin are high. The inductor current builds up
linearly. When the CS pin voltage hits the V_CS(MAX) with
respect to V_IN, the internal MOSFET turns off and the
Schottky diode takes over and returns the current to V_IN.
Then the current through inductor and LEDs starts
decreasing. When CS pin hits V_CS(MIN), the internal
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 MIC3201 has an on board 5V regulator which is for
internal use only. Connect a 1µF capacitor on VCC pin to
analog ground.
The MIC3201 has an EN pin which gives the flexibility to
enable and disable the output with logic high and low
signals.
The MIC3201 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 from 1% to
99%.
February 2011
8
M9999-021011-B