MIC4801 Evaluation Board High Efficiency 600mA Single Channel Linear WLED Driver with Ultra Fast PWM™ Control General Description The MIC4801 is a high efficiency, single channel, White LED (WLED) driver. This constant current linear device is designed to drive a single high power WLED up to 600mA and features a low dropout of 130mV at 400mA (typical). Brightness is controlled through an Ultra Fast PWM™ interface which can operate from 1% to 100% duty cycle. The MIC4801 is available in an 8-pin SOIC leaded package with a junction temperature range of -40°C to +125°C Requirements The MIC4801 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 MIC4801 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, J2 and J3, 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. VBAT is connected to VIN through a 0Ω resistor, R1. 2. Enable/Disable the MIC4801 To enable the device, apply a DC voltage of 1.2V or greater to the EN pin. This allows for full brightness of the WLED (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 40ms forces the MIC4801 into a low IQ sleep mode. Do not leave the EN pin floating as this may cause an indeterminate output state. A pull up resistor of 10kΩ is placed from EN (JP1) to VIN to ensure that the WLED is ON when an input signal is applied. 3. Setting LED current with RSET resistor. The average LED current may be calculated using the equation below: RSET (kΩ) = 4920 ⋅ D + 0.140 I LED (mA) I LED (mA) = 4920 ⋅ D (RSET (kΩ) − 0.140) 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 12.1kΩ which corresponds to ILED of 411mA. 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, D1, should be used when making dropout measurements with a series ammeter. Ordering Information Part Number Description MIC4801YM EV Evaluation board with the Single Channel MIC4801 device Ultra Fast PWM is a trademark 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. MIC4801 Evaluation Board MIC4801 Evaluation Board Schematic VBAT J1 R1 0Ω C2 open C1 2.2µF VIN J2 R2 open VIN R3 10kΩ LED1 MIC4801 EN GND J3 JP1 RSET J4 RSET R4 12.1kΩ D1 J6 D1 GND GND J5 Bill of Materials Item C1 Part Number Manufacturer C1608X5R0J225K TDK 06036D225KAT2A AVX(2) GRM188R60J225KE19D Murata(3) Qty. Ceramic Capacitor, 2.2µF, 6.3V, X5R, Size 0603 1 Open 1 Resistor, 0Ω, 1%, 1/16W, Size 0603 1 (4) VJ0603G225KXYAT Vishay CL10B225KQ8NNNC Samsung CRCW06030000FKEA Vishay (5) C2 R1 Description (1) R2 open R3 CRCW060310K0FKEA Vishay Resistor, 10kΩ, 1%, 1/16W, Size 0603 1 R4 CRCW060312K1FKEA Vishay Resistor, 12.1kΩ, 1%, 1/16W, Size 0603 1 LED1 W42180 Seoul Semiconductor(6) 3.8W High Power WLED 1 U1 MIC4801YM Micrel, Inc.(7) 600mA Single Channel Ultra Fast PWM™ Linear WLED Driver 1 Notes: 1. TDK: www.tdk.com 2. AVX: www.avx.com 3. Murata: www.murata.com 4. Vishay: www.vishay.com 5. Samsung: www.samsung.com 6. Seoul Semiconductor: www.seoulsemicon.com 7. Micrel, Inc.: www.micrel.com March 2011 2 M9999-032111-B Micrel, Inc. MIC4801 Evaluation Board PCB Layout Recommendations Top Layer Bottom Layer March 2011 3 M9999-032111-B Micrel, Inc. MIC4801 Evaluation Board 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. © 2011 Micrel, Incorporated. March 2011 4 M9999-032111-B