MIC3202 Datasheet, PDF (9/19 Pages) Micrel Semiconductor – High-Brightness LED Driver with Integrated MOSFET and High-Side Current Sense

Micrel, Inc.
Functional Diagram
MIC3202
Figure 1. MIC3202/MIC3202-1 Functional Block Diagram
Functional Description
The MIC3202 is a hysteretic step-down driver which
regulates the LED current over wide input voltage range
and capable of driving up to eight 1A LEDs in series.
The device operates from a 6V to 37V input. When the
input voltage reaches 6V, the internal 5V VCC is
regulated and the LX pin is pulled low if the EN pin and
DIM pin are high. The inductor current builds up linearly.
When the CS pin voltage hits V_CS(MAX) with respect to V_IN,
the 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 MOSFET turns on and the cycle repeats.
The frequency of operation depends upon the input voltage,
total LED voltage drop, LED current and temperature. The
calculation for frequency of operation is given in the
Application Information section.
The MIC3202 has an EN pin which gives the flexibility to
enable and disable the output with logic high and low
signals.
The MIC3202 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%.
September 2010
9
M9999-091710-A