MIC2253 Evaluation Board 3.5A 1MHz High Efficiency Boost Regulator with OVP and Softstart General Description The MIC2253 is a high power density 1MHz PWM DC/DC boost regulator. The 3.5A minimum switch current limit combined with a 1MHz switching frequency allows the MIC2253 to use smaller inductors and deliver high power in a tiny solution size. The 2.5V to 10V input voltage range of MIC2253 allows direct operation from 1 and 2 cell Li-ion as well as 3 to 4 cell NiCad, NiMH, Alkaline or lithium batteries. Maximum battery life is assured with a low 0.1µA shutdown current. Requirements The MIC2253 Evaluation board requires a single 10W bench power source adjustable from 2.5V to 10V. The load can either be active (electronic load) or passive (resistor) with the capability to dissipate 7W. It is ideal to have an oscilloscope available to view the circuit waveforms, but not essential. For the simplest test, two voltage meters are required to measure input and output voltage. For efficiency measurements, two voltage meters and two ammeters are required to prevent errors due to measurement inaccuracies. Precautions The evaluation board does not have input reverse polarity protection. Be cautious when connecting the input source to ensure correct polarity is observed. Getting Started 1. Connect an external supply to the VIN (J1) terminal and GND (J4). With the output of the power supply disabled, set its voltage to the desired input test voltage (2.5V ≤ VIN ≤ 10V). An ammeter may be placed between the power supply and the VIN (J1) terminal of the evaluation board. Be sure to monitor the supply voltage at the VIN (J1) terminal, as the ammeter and/or power lead resistance can reduce the voltage supplied to the input. 2. Connect a load to the VOUT (J6) and GND pins (J7) terminals. The load can be either passive (resistor) or active (electronic load). An ammeter may be placed between the load and output terminal. Be sure to monitor the output voltage at the VOUT (J6) terminal. 3. Enable/Disable the MIC2253 (J2). The MIC2253 evaluation board has an Enable pulldown resistor-to-GND. By default the MIC2253 will be disabled and the output voltage will be approximately VIN. By placing a jumper at J5, the enable pin is tied directly to VIN and the output voltage will be enabled when the input supply of ≥2.5V is applied. 4. Over-Voltage Protection. The MIC2253 evaluation board has a 0Ω resistor (R3) connecting the default 5.6V OVP protection circuit to the output. Please see the “Additional Information” section for instructions to externally adjust the OVP voltage. Ordering Information Part Number Description MIC2253-06YML EV Evaluation Board with MIC225306YML 6V OVP Device MLF and MicroLeadFrame are registered trademarks 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 March 2010 M9999-030310-A Micrel, Inc. MIC2253 Evaluation Board Evaluation Board Schematic March 2010 2 M9999-030310-A Micrel, Inc. MIC2253 Evaluation Board Bill of Materials Item C1 Part Number C1608X5R1C225K GRM188R61C225KE15 CL10A225K08NNN C2 C1608X7R1H104K/10 C5 TDK (1) Description Samsung Capacitor, 2.2µF, 16V, X5R, 0603 size Murata Capacitor, 0.1µF, 16V, X7R, 0603 size CL10B104KB8NNN Samsung Capacitor, 0.1µF, 16V, X7R, 0603 size C1608X5R1H103K TDK Capacitor, 10nF, 50V, X5R, 0603 size CL10B103KB8NNN Samsung Capacitor, 10nF, 50V, X5R, 0603 size 06035C103KA12A AVX Capacitor, 10nF, 50V, X5R, 0603 size LMK212BJ226MG-T Samsung Taiyo Yuden AVX Capacitor, 100µF, 16V, D case size C7 C1608C0G1H101J TDK Capacitor, 100pF, 50V, C0G, 0603 size Murata Capacitor, 100pF, 50V, C0G, 0603 size Samsung Capacitor, 100pF, 50V, C0G, 0603 size AVX(5) Capacitor, 100pF, 50V, C0G, 0603 size 06035A101AT2A D1 CMSH3-40M SK32 L1 Central (6) (7) MCC 1 1 1 Schottky Diode, 3A, 20V MCC Schottky Diode, 3A, 40V LTF5022T-2R2N3R2 TDK Inductor, 2.2µH, 3.4A, 5.2 x 5.0 x 2.2mm RLF7030T-2R2M TDK Coilcraft 1 Schottky Diode, 3A, 40V SK34 MOS6020-222ML 1 Capacitor, 22µF, 10V, X5R, 0805 size TPSD107K016R150 CL10C101JB8NNN 1 Capacitor, 22µF, 10V, X5R, 0805 size (4) C6 GRM1885C1H101JA01 1 Capacitor, 2.2µF, 16V, X5R, 0603 size (3) Capacitor, 0.1µF, 16V, X7R, 0603 size CL21A226MPCLRNC Qty. Capacitor, 2.2µF, 16V, X5R, 0603 size Murata(2) TDK GRM188R71H104KA93 C4 Manufacturer Inductor, 2,2µH, 5.4A, 6.8 x 7.3 x 3.2mm(11) (8) Inductor, 2.2µH, 3.56A, 6.0 x 7.1 x 2.4mm 1 (11) R1 CRCW06031002FRTI Vishay(9) Resistor, 10kΩ, 1%, 1/16W, 0603 size 1 R2 CRCW06036200FRTI Vishay Resistor, 620Ω, 1%, 1/16W, 0603 size 1 R3 CRCW06030000FKEA Vishay Resistor, 0Ω, 1%, 1/16W, 0603 size 1 R4 CRCW06031003FRTI Vishay Resistor, 100kΩ, 1%, 1/16W, 0603 size 1 R5 CRCW06033092FRTI Vishay Resistor, 30.9kΩ, 1%, 1/16W, 0603 size 1 1MHz High Power and High Efficiency Boost Regulator 1 U1 MIC2253-06YML Micrel, Inc. (10) Notes: 1. TDK: www.tdk.com 2. Murata: www.murata.com 3. Samsung: www.sem.samsung.com 4. Taiyo Yuden: www.t-yuden.com 5. AVX: www.avx.com 6. Central: www.centralsemi.com 7. MCC: www.mccsemi.com 8. Coilcraft: www.coilcraft.com 9. Vishay: www.vishay.com 10. Micrel, Inc.: www.micrel.com 11. For higher current applications, it is recommended to use the larger inductor specified. March 2010 3 M9999-030310-A Micrel, Inc. MIC2253 Evaluation Board PCB Layout Recommendations Top Layer Bottom Layer March 2010 4 M9999-030310-A Micrel, Inc. MIC2253 Evaluation Board Additional Information Ripple Measurements To properly measure voltage ripple on either the input or output of any regulator with a switching regulator near by, a proper ring in tip measurement is required. Standard oscilliscope probes come with a grounding clip, or a long wire with an alligator clip. Unfortunately, for high frequency measurements, this ground clip can pick up high frequency noise and erroneously inject it into the measured output ripple. The MIC2253 evaluation boards accommodate a home made ring in tip measurement by probing across input and output capacitors. This requires the removing of the oscilloscope probe sheath and ground clip from a standard oscilloscope probe and wrapping a nonshielded bus wire around the oscilloscope probe (as shown on the left). If there does not happen to be any non-shielded bus wire immediately available, the leads from axial resistors will work. By maintaining the shortest possible ground lengths on the oscilloscope probe, true ripple measurements can be obtained. Over-Voltage Protection (OVP) The MIC2253 provides a fixed 5.6V overvoltage protection. The overvoltage functionality will clamp the output voltage to a safe level (5.6V) in the event that a fault condition causes the output voltage to increase beyond control or the OVP pin exceeds 5.6V. To ensure the highest level of protection, the MIC2253 OVP pin will shut the switch off when an overvoltage condition is detected and regulates to the OVP set point. The OVP set point should be set below the rating of the output capacitor to ensure protection. Two external resistors can be used to change the OVP from the range of 5.7V to 30V. Be careful not to exceed the 30V rating of the switch. The OVP feature may be disabled by grounding the OVP pin. The OVP pin is connected internally to a reference voltage via a voltage divider circuit. For a 5.6V OVP setting, connect the OVP pin directly to the output voltage with a 0Ω resistor at R3. To increase the OVP voltage above 5.6V, replace the R3 and R6 resistor values on the evaluation board with the calculated values using the following equation: VOVP = 1.245 × 67 k × (R3 + R 6 ) (15k × R6) VOVP (V) R3 (kΩ) R6 (kΩ) 8.0 13.0 30.1 10 23.7 30.1 12 34.8 30.1 15 51.1 30.1 18 66.5 30.1 20 78.7 30.1 25 105 30.1 30 130 30.1 Table 1. OVP Example Resistor Values 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 to the user. A M9999-030310-A March 2010 5 be reasonably expected to result in a significant injury 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. © 2010 Micrel, Incorporated.