Microchip MIC4812YMME Handleiding

Bekijk gratis de handleiding van Microchip MIC4812YMME (4 pagina’s), behorend tot de categorie Niet gecategoriseerd. Deze gids werd als nuttig beoordeeld door 213 mensen en kreeg gemiddeld 4.5 sterren uit 6 reviews. Heb je een vraag over Microchip MIC4812YMME of wil je andere gebruikers van dit product iets vragen? Stel een vraag

MIC4812 Evaluation Board

High Current 6 Channel Linear WLED

Driver with DAM™ and Ultra Fast

PWM™ Control

Ultra Fast PWM and DAM™Dynamic Averagie Matching are trademarks of Micrel, Inc.

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

General Description

The MIC4812 is a high efficiency linear White LED

(WLED) driver; it is designed to drive up to six high current

WLEDs while maintaining constant current in each

channel. The MIC4812 features Dynamic Average

Matching™ (DAM™) which is specifically designed to

provide optimum matching across all WLEDs. These high

accuracy (±1% typical) current regulated WLED channels

ensure uniform display illumination under all conditions. A

typical dropout of 190mV at 100mA is expected.

The MIC4812 is available in a 10-pin Epad MSOP

package with a junction temperature range of -40°C to

+125°C.

Datasheets and support documentation can be found on

Micrel’s web site at: www.micrel.com

Requirements

The MIC4812 evaluation board requires a power supply

that is capable of delivering at least 1A while providing an

input voltage between 3.0V and 5.5V.

Precautions

The MIC4812 evaluation board is designed for an input

voltage no greater than 6V. This evaluation board does not

have reverse polarity protection; hence, applying a

negative voltage to the VIN terminal may damage the

device.

Getting Started

1. Connect an external supply to VIN. Apply the

desired input voltage across VIN and ground

terminals, J1 and J2, respectively, paying careful

attention to polarity and supply voltage

(3.0V≤VIN≤5.5V). An ammeter may be placed

between the input supply and the VIN terminal to

the evaluation board. Ensure that the supply

voltage is monitored at the VIN terminal. The

ammeter and/or power lead resistance can reduce

the voltage supplied to the input.

2. Enable/Disable the MIC4812

To enable the device, apply a DC voltage of 1.2V or

greater to the EN pin (J3). This allows for full

brightness of the WLEDs (100% duty cycle). The EN

pin can also be used for dimming by connecting a

PWM signal and varying its duty cycle (please refer to

the Ultra Fast PWM™ Dimming Interface Section in

datasheet). Pulling EN low for more than 20ms forces

the MIC4811 into a low IQ sleep mode. Do not leave

the EN pin floating as this may cause an indeterminate

output state. A pull down resistor of 200kΩ is placed from

EN to GND to ensure that the WLEDs are OFF when an

enable signal is not applied.

3. Setting LED current with RSET resistor.

The average LED current may be calculated using the

equation below:

( )

139.0)(

820

)(

139.0

)(

820

)(

−Ω

⋅

=

+

⋅

=Ω

kR

D

mAI

mAI

D

kR

SET

LED

LED

SET

D is the duty cycle of the LED current during PWM

dimming; D=1 when device is fully ON. The stock

evaluation board uses an RSET value of 8.25kΩ which

corresponds to ILED of 10mA.

4. Measuring WLED current.

To measure WLED current, simply insert an ammeter

in series with the WLED(s). Keep in mind that a series

ammeter will add a small voltage drop, so the voltage

at the WLED terminal(s), D1-D6, should be used when

making dropout measurements with a series ammeter.

Ordering Information

Part Number Description

MIC4812YMME EV Evaluation board with Six Channel

WLED Driver

March 2011 M9999-032111-B

Product specificaties