MIC4812YMME Evaluation Board User Guide

MIC4812 Evaluation Board
High Current 6 Channel Linear WLED
Driver with DAM™ and Ultra Fast
PWM™ Control
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:
RSET (kΩ) =
820 ⋅ D
+ 0.139
I LED (mA)
I LED (mA) =
820 ⋅ D
(RSET (kΩ) − 0.139)
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
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
March 2011
M9999-032111-B
Micrel, Inc.
MIC5337 Evaluation Board
MIC4812 Evaluation Board Schematic
Bill of Materials
Item
Part Number
Manufacturer
Description
Qty
Ceramic Capacitor, 2.2µF, 6.3V, X5R, Size 0603
1
WLED
6
(1)
C1608X5R0J225K
TDK
06036D225KAT2A
AVX(2)
GRM188R60J225KE1
9D
Murata(3)
VJ0603G225KXYAT
Vishay(4)
LED1–
LED6
OVS5WBCR4
OPTEK Technology, Inc(5)
R1
CRCW06038K25F5EA
Vishay(4)
Resistor, 8.25k, 1%, 1/16W, Size 0603
1
R2
CRCW06032003FKEA
Vishay(4)
Resistor, 200k, 1%, 1/16W, Size 0603
1
U1
MIC4812YMME
Micrel, Inc.(6)
High Current 6 Channel Linear WLED Driver
with DAM™ and Ultra Fast PWM™ Control
1
C1
Notes:
1. TDK: www.tdk.com
2. AVX: www.avx.com
3. Murata: www.murata.com
4. Vishay: www.vishay.com
5. OPTEK: www.optekinc.com
6. Micrel, Inc.: www.micrel.com
March 2011
2
M9999-032111-B
Micrel, Inc.
MIC5337 Evaluation Board
PCB Layout Recommendations
Top Layer
Bottom Layer
March 2011
3
M9999-032111-B
Micrel, Inc.
MIC5337 Evaluation Board
Package Information
10-Pin EPAD MSOP (MME)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This
information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability
whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical
implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
March 2011
© 2011 Micrel, Incorporated.
4
M9999-032111-B