MIC4744YML Evaluation Board Dual 2A Buck Regulator General Description The Micrel MIC4744 is a high efficiency dual PWM buck (step-down) regulator that provides up to 2A of output current for each channel. The MIC4744 operates at 4MHz and has proprietary internal compensation that allows a closed loop bandwidth of over 200kHz. The low on resistance internal P-Channel MOSFET of the MIC4744 allows efficiencies up to 90%, reduces external component count and eliminates the need for an expensive external current sense resistor. The MIC4744 operates from a 2.9V to 5.5V input and its output is adjustable down to 0.6V. The devices can operate with a maximum duty cycle of 100% for use in low-dropout applications. 3. Enable the MIC4744. The enable pins are connected to pull up resistors. Both outputs of the MIC4744 turn on when VIN exceeds the UVLO threshold at the VIN pin. Each output of the MIC4744 may be turned off by shorting the enable pin to ground or bringing the enable pin below the enable threshold. An external connection on the board provides easy access to the enable pin. Output Voltage The output voltages on the MIC4744 evaluation board are adjustable. The output voltage is controlled by the feedback resistors (R11 and R12 for VOUT1, R21 and R22 for VOUT2) and can be calculated as follows: Requirements VOUT 1 = VREF × (1 + R11 ) R12 The MIC4744 evaluation board requires an input power source that is able to deliver greater than 2.9V at over 4A. The output load can either be an active or passive load. VOUT 2 = VREF × (1 + R 21 ) R 22 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 MIC4744 evaluation board is 5.5V. Exceeding 6V on the input could damage the device. Where VREF = 0.6V. The evaluation board is preset at 1.8V for VOUT1 and 1.2V for VOUT2, but can easily be modified by removing R12 or R22 and replacing them with the value that yields the desired output voltage. R12 = R11 × VREF VOUT − VREF R 22 = R 21 × VREF VOUT − VREF Getting Started 1. Connect an external supply to VIN terminal. Apply desired input voltage to the VIN and ground terminals of the evaluation board, paying careful attention to polarity and supply voltage (2.9V<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 VOUT1/VOUT2 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 VOUT1/VOUT2 terminal. Ensure the output voltage is monitored at the VOUT1/VOUT2 terminal. The default VOUT1 is set to 1.8V and the default VOUT2 is set to 1.2V. This can be adjusted by changing the feedback resistors. See “Output Voltage.” For VREF = 0.6V, this reduces to: R12 = R11 × 0.6V VOUT − 0.6V R 22 = R 21 × 0.6V VOUT − 0.6V Ordering Information Part Number Description Package MIC4744YML IC 16-Pin EPAD-MLF® MIC4744YML EV Evaluation Board 16-Pin EPAD-MLF® MLF is a registered trademark of Amkor Technology, 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 February 2009 M9999-021709-B Micrel, Inc. MIC4744YML Evaluation Board Evaluation Board Schematic Bill of Materials Item Part Number C11,C12 GRM188R60J106M C21,C22 C1608X5R0J106M Manufacturer TDK(2) 10µF Ceramic Capacitor, X5R, Size 0603, 6.3V 6 680pF Ceramic Capacitor, NPO, Size 0603, 6.3V 2 Vishay 82pF Ceramic Capacitor, NPO Size 0603, 10V 2 VJ0603Y104KXXAT Vishay(4) 0.1µF Ceramic Capacitor, X7R, Size 0603, 25V 5 SS2P3L Vishay(4) SSA23L Vishay(4) 2A Schottky 30V 2 0.47µH Inductor 20mΩ 4.45mm(L) x 4.06mm(W) x 1.2 mm(H) 2 10kΩ, 1%, Size 0603 Resistor 2 06036D106KMAT2A C13*,C23* VJ0603A681KXXCW Vishay(4) VJ0603A820KXXCW (4) C18,C28 D1,D2 C16,C26,C7 L1,L2 (3) AVX (5) B230A Diodes IHLP1616AB-01 R47 Vishay(4) R11,R12 CRCW060310K0FKXX R12,R22 CRCW06033K16FKXX (4) Vishay 3.16kΩ, 1%, Size 0603 Resistor For 2.5VOUT CRCW06034K99FKXX CRCW06036K65FKXX February 2009 Qty Murata C15,C25 C14,C24 Description (1) 4.99kΩ, 1%, Size 0603 Resistor For 1.8 VOUT (4) Vishay 6.65kΩ, 1%, Size 0603 Resistor For 1.5 VOUT CRCW060310K0FKXX 10kΩ, 1%, Size 0603 Resistor For 1.2 VOUT CRCW060315K0FKXX 15kΩ, 1%, Size 0603 Resistor For 1.0 VOUT 2 2 M9999-021709-B Micrel, Inc. MIC4744YML Evaluation Board Bill of Materials (continued) Item R13*, R23* R14, R24 R5 U1 Part Number CRCW06032R70FKXX CRCW060349K9FKXX CRCW060310R0FKXX MIC4744YML Manufacturer Description Qty (4) 2.7Ω, 1%, Size 0603 Resistor 2 (4) 49.9kΩ, 1%, Size 0603 Resistor 2 10Ω, 1%, Size 0603 Resistor 1 Dual 2A 2MHz Integrated Switch Buck Regulator 1 Vishay Vishay (4) Vishay Micrel, Inc. (7) Notes: 1. Murata: www.murata.com 2. TDK: www.tdk.com 3. AVX: www.avx.com 4. Vishay: www.vishay.com 5. Cooper: www.cooperbussmann.com 6. Diode: www.diodes.com 7. Micrel, Inc: www.micrel.com *only for ultra-low noise applications. February 2009 3 M9999-021709-B Micrel, Inc. MIC4744YML Evaluation Board Printed Circuit Board Layouts Figure 1a. Top Layer Figure 1b. Bottom Layer February 2009 4 M9999-021709-B Micrel, Inc. MIC4744YML Evaluation Board Figure 1c. Mid-Layer 1 Figure 1d. Mid-Layer 2 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 The 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. © 2008 Micrel, Incorporated. February 2009 5 M9999-021709-B