Microchip MIC3202YME Manual

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Side 1/7

MIC3202/MIC3202-1

Evaluation Board

High-Brightness LED Driver with Integrated

MOSFET and High-Side Current Sense

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

October 2010 M9999-102810

General Description

The MIC3202/MIC3202-1 is a hysteretic step-down,

constant-current, High-Brightness LED (HB LED) driver.

It provides an ideal solution for interior/exterior lighting,

architectural and ambient lighting, LED bulbs, and other

general illumination applications.

This board enables the evaluation of the

MIC3202/MIC3202-1 for 1A LED current. The board is

optimized for ease of testing, with all the components on

a single side. The device operates from a 6V to 37V

input voltage range, and includes an integrated 1.0A

MOSFET. When the input voltage approaches and

crosses UVLO threshold, 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 VIN, the internal MOSFET is turned 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 VCS(MIN), the internal

MOSFET is turned on and the cycle repeats.

Since the control scheme does not need loop

compensation, it makes for a very simple design and

avoids problems of instability.

Datasheets and support documentation can be found on

Micrel’s web site at: www.micrel.com.

Requirements

This board needs a single-bench power source

adjustable over the input voltage of 6V < V IN < 37V that

can provide at least 1A of current. The loads can either

be active (electronic load in CV mode) or passive

(LEDs) with the ability to dissipate the maximum load

power while keeping accessible surfaces ideally <70°C.

Precautions

There is no reverse input protection on this board. When

connecting the input sources, ensure that the correct

polarity is observed.

In the line transient condition, such as hot plug-in, an

electrolytic capacitor may be required at the VIN and

GND terminals in order to prevent IC damage from a

surge voltage.

Getting Started

1. Connect VIN supply to the input VIN and GND

terminals. With the output of this supply disabled,

set the supply voltage to the desired input test

voltage (6V < VIN < 37V). This supply voltage should

be monitored at the test boards input terminals to

allow voltage drops in the test cables (and ammeter

if used) to be accounted for. An ammeter can be

added inline with the +VIN input terminal to

accurately measure input current.

2. Connect the LEDs to the output terminals

between LED+ and LED−

−

−−. This LED voltage drop

depends on manufacturer tolerance and number of

LEDs. The LED current can be measured using an

ammeter or current probe. A 4.7µF ceramic

capacitor helps to reduce the current ripple through

the LED. The LED current is set to 1A by a 200mΩ

current-sense resistor (RCS).

3. Enable the input supply. By default, the IC is

enabled when the input voltage crosses the VIN

threshold (4V) and the internal VCC regulator and

internal MOSFET are turned on with the EN and

DIM pins are high. To use the EN and DIM functions

of the MIC3202/MIC3202-1, a test point is provided

for each of them.

Ordering Information

Part Number Description

MIC3202YME EV MIC3202YME Evaluation Board

Micrel, Inc. MIC3202/MIC3202-1 Evaluation Board

October 2010 2 M9999-102810

Other Features

EN Input

The EN pin provides a logic level control of the output

and the voltage has to be 2.0V or higher to enable the

current regulator. The output stage is gated by the DIM

pin. When the EN pin is pulled low, the regulator goes to

off-state and the supply current of the device is reduced

to below 1µA. Do not drive the EN pin above the supply

voltage.

DIM Input

The DIM pin provides a logic level control for brightness

of the LED. A PWM input can be used to control the

brightness of LED. DIM high enables the output and its

voltage has to be 2.0V or higher. DIM low disables the

output, regardless of EN high-state.

Current-Sense Input

The CS pin provides the high-side current sense to set

the LED current with an external sense resistor.

A sense resistor RCS is placed between VIN and LED+

terminals.

The current through LED is sensed by the sense resistor

(RCS). The sensed voltage is fed back to the MIC3202 to

regulate the LED current

RCS is given by:

)

V+V

LED

)MIN(CS)MAX(CS

CS Error!

Bookmark not defined.

ILED is LED current required to set.

RCS (Ω) ILED (A) I2R (W) Size (SMD)

1.33 0.15 0.03 0603

0.56 0.35 0.07 0805

0.4 0.5 0.1 0805

0.28 0.7 0.137 0805

0.2 1.0 0.2 1206

For VCS(MAX) and VCS(MIN) refers to the Electrical

Characteristics table.

Frequency of Operation

To calculate the frequency spread across input supply:

)V+V(×IΔ×L

)VR×IV(×)V+R×I+V(

INDL

LEDCSLEDINLEDCSLEDD

)MIN(CS)MAX(CS

=IΔ

where:

VD is Schottky diode forward drop

VLED is total LEDs voltage drop

VIN is input voltage

ILED is average LED current

According to the above equation, choose the inductor to

make the operating frequency no higher than 1MHz.

Refer to the datasheet Application Information for more

information on components selection guidelines.

Frequency Dithering

The MIC3202 is designed to modulate the V CS(MAX) with

amplitude ±6mV by a pseudo random generator to

generate the ±12% of the switching frequency dithering.

This spreads the frequency spectrum over a wider range

and reduce the EMI noise peaks.

The MIC3202-1 is non-dithering version of the MIC3202.

Produkt Specifikationer

Mærke:	Microchip
Kategori:	Ikke kategoriseret
Model:	MIC3202YME

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