MIC4812YMME-EV

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