MIC4682 Evaluation Board Micrel, Inc. MIC4682 Evaluation Board Programmable Current Limit SOP-8 SuperSwitcher™ 4V to 34V Input / 200kHz is forward biased. During this portion of the cycle, current flows through the diode, inductor and load. Figure 2 shows the 5V output efficiency versus input voltage and continuous output current. General Description The MIC4682 is an easy-to-use adjustable step-down (buck) switch-mode voltage regulator, with 10% programmable current limit. The current-limit feature makes the MIC4682 ideal for constant-voltage constant-current applications, such as simple battery chargers. The 200kHz MIC4682 achieves 2.1A peak output current in a small SOP-8 across a 4V to 34V input voltage range. In shutdown mode, the MIC4682 draws typically 1µA standby current. The regulator performs cycle-by-cycle current limiting and thermal shutdown for protection under fault conditions. The MIC4682 requires a minimum number of external components and can operate using a standard series of inductors. The MIC4682 is available in the 8-lead SOP with a –40°C to +125°C junction temperature range. Precautions MIC4682 has no protection from reversed polarity being applied to its input. Any momentary reversal of the dc power supply connections can cause permanent damage to the circuit. Use extreme care with these connections. The safest way to power up the MIC4682 evaluation board is to set the power supply to zero Volts, and then gradually increase the supply voltage. Monitor the input supply current while increasing the input voltage. If the circuit draws excessive current with no load applied (greater than 100mA) then there is probably a problem with the set-up. Immediately shut off the main power supply and check for proper power supply connections. This simple procedure can avoid most catastrophic failures. Warning: Tantalum capacitors may explode if improperly connected. Always wear safety glasses when operating the evaluation board. The maximum input voltage to the board is 34V. The tantalum output capacitor is rated at 10V. Do not exceed 10V. Requirements The MIC4682 evaluation board requires a power supply capable of at least 2.5A at up to 34V. The load should be capable of delivering 2.0A peak under normal operation or 3A in current limit. Operation Figure 1 shows the schematic of the evaluation board circuit. When the internal high-side switch turns on, one side of the inductor is fed from the input voltage, charging the inductor (+) and (–). During this period, current flows from the input, through the internal switch, inductor and load. When the internal switch turns off, the inductor polarity switches to (–) and (+), the SW pin voltage drops until the freewheeling diode 90 Efficiency vs. Output Current EFFICIENCY (%) 80 70 60 50 40 VIN = 7.5V VIN = 12V VIN = 24V VIN = 30V 30 20 10 VOUT = 5V 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 OUTPUT CURRENT (A) Figure 2. 24.9k Figure 1. Evaluation Board Schematic SuperSwitcher is a trademark of Micrel, Inc. Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 474-1000 • fax + 1 (408) 474-1000 • http://www.micrel.com March 2005 1 MIC4682 Evaluation Board MIC4682 Evaluation Board Micrel, Inc. Current Limit Setting Output Voltage Setting Two options of current limit are provided on the evaluation board. To select the current limit, place the shorting jumper across the proper pins of header JP3. See "Typical Characteristics: Current Limit vs. RISET at TJ = 25°C", from the MIC4682 data sheet for more detailed information. Do not short or float the ISET pin. Shorting the ISET pin will set the peak current limit above 2A. Floating the ISET pin will exhibit unstable conditions. Jumper Current Limit JP3a 0.6A JP3b 1.0A Table 1. Typical Current Limit Four standard voltages may be selected by placing the shorting jumper across the proper pins of header JP2. If a non-standard output voltage is desired, resistor value R5 is calculated by the following equation. R5 = R1 VOUT –1 VFB VFB = 1.23V Jumper Output Voltage JP2a 1.8V JP2b 2.5V JP2c 3.3V JP2d 5.0V Table 2. Typical Output Voltage Typical Safe Operating Area (SOA)(1) 5V Output SOA TA = 25°C 1.2 1 TA = 60°C 0.8 0.6 VOUT = 5V TJ = 125°C D = Max Peak ILIMIT= 2A 0.4 0.2 0 0 5 OUTPUT CURRENT (A) 1.2 1 TA = 60°C 0.8 0.6 VOUT = 3.3V TJ = 125°C D = Max Peak ILIMIT= 2A 0.4 0.2 0 0 10 15 20 25 30 35 40 INPUT VOLTAGE (V) TA = 25°C 1.6 1.4 5 2.5V Output SOA 2 TA = 25°C 1.4 1.2 TA = 60°C 1.0 0.8 VOUT = 2.5V TJ = 125°C D = Max Peak ILIMIT= 2A 0.6 0.4 5 1.8 1.6 TA = 25°C 1.4 1.2 TA = 60°C 1 0.8 VOUT = 1.8V TJ = 125°C D = Max = 2A Peak I 0.6 0.4 0.2 0 0 10 15 20 25 30 35 40 INPUT VOLTAGE (V) 10 15 20 25 30 35 40 INPUT VOLTAGE (V) 1.8V Output SOA 2 1.8 1.6 0.2 0 0 OUTPUT CURRENT (A) 1.6 1.4 3.3V Output SOA 2 1.8 OUTPUT CURRENT (A) OUTPUT CURRENT (A) 2 1.8 LIMIT 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) Note 1. SOA measured on the MIC4682 evaluation board. MIC4682 Evaluation Board 2 March 2005 MIC4682 Evaluation Board Micrel, Inc. Printed Circuit Layout March 2005 Figure 3a. Top Silkscreen Figure 3c. Bottom Silkscreen Figure 3b. Top Layer Figure 3d. Bottom Layer 3 MIC4682 Evaluation Board MIC4682 Evaluation Board Micrel, Inc. Bill of Materials Item Part Number Manufacturer Description U1 MIC4682BM Micrel Semiconductor1 Programmable Current Limit Buck Regulator 1 C1 GRM55DR61H106KA88L Murata7 10µF/50V, Ceramic, X5R 1 C3, C7 VJ0805Y104KXAMT Vishay Vitramon3 0.1µF/50V 2 593D227X0010D2T Vishay Sprague2 C2, C4, C6 C5 Qty. Optional Inc.4 220µF/10V 1 Schottky 3A, 40V 1 D1 B340A SS34A Diode, L1 CDRH127-680MC Sumida5 68µH 1 R1 CRCW08053011FRT1 Vishay-Dale6 3.01k, 1% 1 R2 CRCW08059760FRT1 Vishay-Dale6 976Ω, 1% 1 CRCW08051781FRT1 Vishay-Dale6 1.78k, 1% 1 R4 CRCW08052941FRT1 Vishay-Dale6 2.94k, 1% 1 R5 CRCW08056491FRT1 Vishay-Dale6 6.49k, 1% 1 R6 CRCW08052492FRT1 Vishay-Dale6 24.9k, 1% 1 R7 CRCW08051622FRT1 Vishay-Dale6 16.2k, 1% 1 R8 — — Optional — R9 CRCW08051005FRT1 Vishay-Dale6 10M, 1% 1 J1-J4 2551-2-00-01-00-00-07-0 Millmax Turrets pins 4 R3 JP1, JP2, JP3 Jumpers 1. Micrel Semiconductor, tel: 408-944-0800, http://www.micrel.com 2. Vishay Sprague Inc., tel: 207-490-7256, http://www.vishay.com 3. Vishay Vitramon Inc., tel: 203-452-5615, http://www.vishay.com 4. Diode, Inc., tel: 805-446-4800, http://www.diodes.com 5. Sumida, tel: 510-668-0600, http://www.sumida.com 6. Vishay-Dale, tel: 402-644-4218, http://www.vishay.com 7. Murata, tel: 770-436-1300, http://www.murata.com 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. © 2002 Micrel, Incorporated MIC4682 Evaluation Board 4 March 2005