MIC2182 Evaluation Board Micrel MIC2182 Evaluation Board Synchronous Buck 4A Evaluation Board Do not exceed the 10V maximum rating of the output capacitors. Jumper JP3 is hard wired in the evaluation board. This prevents accidental removal of the jumper when the adjustable version of the MIC2182 is used. If JP3 is removed when using the adjustable version, the controller may run at maximum duty cycle causing the output voltage to rise up near the input voltage. The output tantalum capacitors will be damaged or may catch fire if their voltage rating is exceeded. General Description This evaluation board provides a platform for evaluating the MIC2182 synchronous buck controller IC. The evaluation board schematic is shown in Figure 1. The board comes with the adjustable version of the MIC2182. Jumpers allow easy selection of preset or custom output voltages and operating modes. The board provides 4A output current, while only occupying 1.9 in2 board space. Full-load efficiency is better than 90%. The MIC2182 switches at a nominal frequency of 300kHz with the capability to synchronize up to higher frequencies. Please refer to the MIC2182 data sheet for a detailed explanation of the MIC2182 and synchronous buck converter operation. Specifications Recommended Operating Input Voltage .......... 4.5V to 28V Maximum Input Voltage ................................................ 28V Output Voltage .................................................. selectable* Maximum Output Current ................................................ 4A Getting Started 1. Connect an input voltage source to VIN terminal (J1) and GND terminal (J7). An ammeter may be placed between the source and VIN terminal to monitor input current. Connect a load to the output terminal (J8) and GND terminal (J6). An ammeter may be used at the output as well. Using banana jacks or hard wiring the connections to the board instead of using the terminal pins may reduce the contact resistance of these connections. 2. Select the output voltage with jumper JP4. Make sure jumpers JP3 and JP2 are installed and jumper JP1 is set for the desired mode of operation. See Table 1 for jumper configurations. 3. Apply 5V to the input. The output voltage, measured at terminals J7 and J8, should be at the selected value. 4. The switching waveform (VSW) may be monitored with an oscilloscope at the input side of the inductor L1 (junction of the inductor and C6 on the PCB). If the waveform is difficult to trigger, the converter may be operating in skip mode. Either install jumper JP1 (forcing PWM mode) or increase the output current to 2A. Output Voltage Selection Four standard voltages may be selected by placing the shorting jumper across the proper pins of header JP4, as * 1.8V, 2.5V, 3.3V, or resistor programmable 1.3V to 6V Requirements A power source capable of supplying 4A is recommended. The output may be loaded with a resistive or active load. An active load may be set for constant current or constant resistance mode. Precautions This evaluation board does not have input reverse polarity protection. Applying a negative voltage at the VIN terminal (with respect to ground) may permanently damage the components on the board. The maximum input capacitor voltage is 35V. Exceeding this voltage will damage both the capacitors and the MIC2182. The tantalum output capacitors are rated at 10V. Jumper Open Closed JP1 Automatic PWM/skip-mode selection Forced PWM-mode operation JP2 External sync No external sync Jumper Output Voltage Connects external feedback for MIC2182BM controller See “ Precautions.” JP4a 1.8V JP4b 2.5V JP3 Disconnects external feedback for MIC2182-3.3BM or MIC2182-5.0BM fixed controllers JP4c 3.3V JP4d 5.0V Table 1a. Operating Configuration Jumpers Table 1b. Output Voltage Jumpers Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com February 2000 1 MIC2182 Evaluation Board MIC2182 Evaluation Board MIC2182 Evaluation Board J1 VIN C11 22µF 35V J8 GND J2 UVLO R7 100k 10 C5 0.1µF R8 open 6 J3 PWM 2 2 MODE: OPEN = AUTO CLOSED = PWM JP1 J4 SYNC J5 GND R1 10k 11 BST 14 EN/UVLO HSD 16 PWM 15 VSW D2 SD103BWS C6 0.1µF C9 4.7µF 16V R9 LSD 3 5 13 PGND 12 COMP CSH 8 SYNC VOUT 9 FB/VREF 7 SS C2 1nF SGND JP2 SYNC: OPEN = EXTERNAL CLOSED = INTERNAL 4 Q2 Si4800DY L1 10µH OPTION OPTION C4 1nF 1 C3 0.1µF U1 MIC2182BSM VIN VDD C10 22µF 35V R6 Q1 Si4800DY D1 B140 R2 0.020Ω J6 VOUT R5 OPTION C7 220µF 10V C14 OPTION C13, 1nF C1, 0.1µF FIXED VERSIONS ONLY C8 220µF 10V C15 OPTION C12 0.1µF 50V J7 GND R4 10k JP3 DEVICE VERSION: OPEN = FIXED CLOSED = ADJ. MUST BE CONNECTED FOR ADJUSTABLE VERSION SEE PRECAUTIONS ON PAGE 1. JP4 OUTPUT VOLTAGE SELECTION R14 22.6k R13 10k R12 6.04k R3 3.32k 1.8V 2.5V 3.3V 5V Figure 1. Evalutation Board Schematic Micrel February 2000 MIC2182 Evaluation Board Micrel illustrated in the output voltage jumper chart. A custom programmed voltage may be obtained by replacing R3 with the appropriate value resistor. For a desired output voltage, resistor value R3 is calculated by the following equation: R3 = R8 = where: VIN = desired input voltage when the MIC2182 starts switching R7 = 100kΩ (supplied with the evaluation board) Additional Features Resistor locations R9 and R6, on the back of the board, are used to slow down or dampen the gate drive signal to the MOSFETs. The etch shorting the resistor pads must be cut before the resistor is inserted. An RC snubber can be used in locations C14 and R5, on the back of the board, to dampen the VSW waveform. Capacitor location C15 is provided if additional compensation of the voltage control loop is required. 1.245 × R4 VOUT − 1.245 where: R4 = 10kΩ Fixed vs. Adjustable Versions The evaluation board comes with an adjustable version of the MIC2182. To use one of the fixed output voltage versions of the MIC2182, jumper JP3 must be removed and a 0.1µF ceramic capacitor must be soldered in location C1. Input Undervoltage Lockout Resistors R7 and R8 set the input undervoltage lockout feature. When pin 6 (UVLO) is pulled up to VIN, the MIC2182 typically starts switching at an input voltage of 4.4V. The startup voltage is increased using the R7-R8 voltage divider. The formula to calculate the turn on voltage is: February 2000 2.5 × R7 VIN − 2.5 3 MIC2182 Evaluation Board MIC2182 Evaluation Board Micrel Bill of Materials Item Part Number Manufacturer U1 MIC2182BSM Micrel Q1, Q2 Si4800DY D1 B140 D2 SD103BWS CMDSH2-3 L1 CDRH127-100 Description Qty. high-eff. synchronous buck controller 1 Vishay/Siliconix MOSFET 2 Vishay/Lite-On 1A 40V, Schottky 1 100mA 30V, Schottky 1 10µH 5A 1 AVX 0.1µF 25V, X7R ceramic 0 AVX 1nF 50V, X7R ceramic 3 Vishay/Lite-On Central Semiconductor Sumida C1* C2, C4, C13 08055C102MAT2A C3, C5, C6, C12 08055C104MAT2A AVX 0.1µF 25V, X7R ceramic 4 C7, C8 TPSE227M010R0100 AVX 220µF 10V, tantalum 2 C9 TAJA475M016R AVX 4.7µF 16V, tantalum 1 C10, C11 TPSE226M035R0300 AVX 22µF 35V, tantalum 2 AVX open (0805 size) C14, C15 R1, R4, R13 CRCW08051002FRT1 Vishay/Dale 10k ±1% 3 R2 WSL-2010-R020-F LR2010-01-R020-F Vishay/Dale IRC 0.020Ω ±1% (2010 size) 1 R3 CRCW08053321FRT1 Vishay/Dale 3.32k ±1% 1 open 4 R5, R6, R8, R9 R7 CRCW08051003FRT1 Vishay/Dale 100k ±1% 1 R12 CRCW08056041FRT1 Vishay/Dale 6.04k ±1% 1 R14 CRCW08052262FRT1 Vishay/Dale 22.6k ±1% 1 J1–J8 2551-2-00-01-00-00-07-0 turret pin 8 JP1–JP3 S1012-02-ND (PTC26SAAN) Sullins 1×2 header 3 JP4 S2012-04-ND (PTC36DAAN) Sullins 4×2 header 1 — 929955-06 jumper 1 Mill-Max 3M * Used with MIC2182-x.xBSM (fixed) applications only. Vendor Telephone Number Vishay/Lite-On (805) 446-4800 Vishay/Dale (402) 644-4218 Vishay/Siliconix (408) 988-8000 Central Semiconductor (516) 435-1110 Sumida (847) 956-0666 AVX (803) 448-9411 Component Vendors MIC2182 Evaluation Board 4 February 2000 MIC2182 Evaluation Board Micrel Printed Circuit Layouts February 2000 Top-Side Silk Screen Bottom-Side Silk Screen Top-Side Copper Bottom-Side Copper 5 MIC2182 Evaluation Board MIC2182 Evaluation Board MIC2182 Evaluation Board Micrel 6 February 2000 MIC2182 Evaluation Board February 2000 Micrel 7 MIC2182 Evaluation Board MIC2182 Evaluation Board Micrel MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB USA http://www.micrel.com This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. © 2000 Micrel Incorporated MIC2182 Evaluation Board 8 February 2000