MIC4722 Evaluation Board 3mm × 3mm 2.75MHz Converter General Description The Micrel MIC4722 is a high efficiency PWM buck (step-down) regulator that provides up to 3A of output current. The MIC4722 operates at 2.7MHz and has proprietary internal compensation that allows a closed loop bandwidth of over 200 KHz. The low on-resistance internal p-channel MOSFET of the MIC4722 allows efficiencies over 94% and reduces external component count and eliminates the need for an expensive current sense resistor. The MIC4722 operates from 2.7V to 5.5V input and the output can be adjusted down to 1V. The devices can operate with a maximum duty cycle of 100% for use in low-dropout conditions. Requirements The MIC4722 evaluation board requires an input power source that is able to deliver greater than 2.7V at over 3A. The output load can either be an active or passive source. Precautions The evaluation board does not have reverse polarity protection. Applying a negative voltage to the VIN terminal may damage the device. In addition, the maximum operating voltage of the MIC4722 evaluation board is 5.5V. Exceeding 6V on the input could damage the device. For short circuit testing, an additional input capacitor over 22uF is required. This is preferably an electrolytic, but may be tantalum or ceramic. When using long test leads to provide power to the device, the inductance can be over 1uH. During a short circuit condition, the high peak currents through the test leads may cause the input voltage to spike and exceed the absolute maximum rating of 6V, possibly damaging the device. Getting Started 1. Connect an external supply to VIN. Apply desired input voltage to the VIN and ground terminals of the evaluation board, paying careful attention to polarity and supply voltage (2.7V<VIN<5.5V). An ammeter may be placed between the input supply and the VIN terminal to the evaluation board. Ensure 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. Connect the load to the VOUT and ground terminals. The load can be either passive (resistive) or active (as in an electronic load). An ammeter can be placed between the load and the VOUT terminal. Ensure the output voltage is monitored at the VOUT terminal. The default output voltage is set to 1.8V. This can be adjusted by changing the feedback resistors. See “Output Voltage.” 3. Enable the MIC4722. Apply a 1.3V or greater voltage source to the enable pin. Output Voltage The output voltage on the MIC4722 evaluation board is adjustable. The output voltage is controlled by the feedback resistors (R1 and R2) and can be calculated as follows: ⎛ R1 ⎞ VOUT = 1V × ⎜ + 1⎟ ⎝ R2 ⎠ The evaluation board is initially adjusted to 1.8V, but can easily be modified by removing R2 and replacing it with the value that yields the desired output voltage. (Removing R2 sets the output to 1V.) R2 = 10k Ω ⎛ V OUT ⎞ − 1⎟ ⎜ ⎝ 1V ⎠ 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 2007 M9999-101107-B Micrel, Inc. MIC4722 Evaluation Board Evaluation Board Schematic J4 PGOOD R3 10k C12 Open 11 R4 10 5 C7 0.1µF/10V 8 J3 EN VIN SW SW FB EN NC 10 L1 0.47µH J5 VOUT 1 12 D1 SSA33L BIAS 3 7 VIN 2 C6 10µF 2 C8 82pF R1 10k 6 AGND C5 10µF 1 C9 4.7µF C10 Open C11 Open R2 12.4k 4 2 J1 +VIN U1 MIC4722YML 9 C4 Open PGOOD C3 Open PGND C2 Open PGND C1 Open J6 GND J2 GND Bill of Materials Item C1-4, C10-12* C5, C6 C7 C8 C9 Part Number Manufacturer Description C1005X7R1C104K TDK(1) OPEN (0.1µF Ceramic Capacitor X7R 16V) GRM155R601A104M Murata(2) OPEN (0.1µF Ceramic Capacitor X5R 10V) (3) OPEN (0.1µF Ceramic Capacitor X7R 10V) VJ0402Y104KXQCW1BC Vishay C1608X5R0J106K TDK(1) GRM188R60J106M Murata(2) VJ0402Y104KXQCW1BC Vishay(3) TDK VJ0402A820KXXCW1BC Vishay(3) TDK C1680JFOJ475Z TDK(1) 2 0.1µF Ceramic Capacitor X7R 10V 1 0.1µF Ceramic Capacitor X7R 16V 82pF Ceramic Capacitor NPO 25V (1) C1005COG1H820J * 10µF Ceramic Capacitor X5R 6.3V (1) C1005X7R1C104K Qty. 1 82pF Ceramic Capacitor 50V 4.7µF Ceramic Capacitor 6.3V (2) 1 GRM188R60J475KE19D Murata SSA33L Vishay(3) MBRM330-13 Diodes, Inc.(4) SPM6530T-R47M170 TDK(1) 0.47µH Inductor 3.63mΩ 7.1mm (L) x 6.8mm (W) x 3mm (H) IHLP2525AHERR47M01 Vishay(3) 0.47µH Inductor 8.4mΩ (L) 6.47mm x (W) 6.86mm x (H) 1.8mm R1, R3 CRCW04021002FKEYE3 Vishay Dale(3) 10k 1% 0402 1/16W Resistor 1 R2 CRCW04021242FKEYE3 Vishay Dale(3) 12.4k 1% 0402 1/16W Resistor 1 R4 CRCW040210R0FKEYE3 Vishay Dale(3) 10 1% 0402 1/16W Resistor 1 U1 MIC4722YML Micrel(5) 2.7MHz 3A Buck Regulator 1 D1 L1 4.7µF Ceramic Capacitor X5R 6.3V 3A Schottky 30V 1 Notes: 1. TDK: www.tdk.com 2. Murata: www.murata.com 3. Vishay: www.vishay.com 4. Wurth Elektronik: www.we-online.de 5. Micrel, Inc.: www.micrel.com October 2007 2 M9999-101107-B 1 Micrel, Inc. MIC4722 Evaluation Board Printed Circuit Board Layouts Top Layer Bottom Layer October 2007 3 M9999-101107-B Micrel, Inc. MIC4722 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 This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. 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. © 2006 Micrel Incorporated October 2007 4 M9999-101107-B