MIC22400YML Evaluation Board Integrated 4A Synchronous Buck Regulator General Description This board enables the evaluation of the MIC22400; a high-power density, frequency-adjustable synchronous buck regulator. The MIC22400 features, integrated 4A MOSFETs, integrated frequency compensation, flexible sequencing and tracking abilities. The board is optimized for ease of testing, so all major components are on a single side. The voltage mode feedback loop is designed to allow high bandwidth with just two external compensation components. The high-side MOSFET is PChannel allowing duty cycle control up to 100%. The Micrel MIC22400 is a high-efficiency 4A integrated synchronous buck (step-down) regulator. The MIC22400 is optimized for highest power density and achieves over 85% efficiency whilst switching at 4MHz with only 1uH inductor and down to 22µF output capacitor. The ultra-high speed control loop keeps the output voltage within regulation even under extreme transient load swings commonly found in FPGAs and low voltage ASICs. The output voltage can be adjusted down to 0.7V to address all low-voltage power needs. A full range of sequence options are available with the MIC22400. The EN/DLY pin combined with the power POR pin allows multiple outputs to be sequenced in any way on turn on and turn off. The RC (Ramp Control™) pin allows the device to be connected to another MIC2240x family of products to keep the output voltages within a certain delta V on start-up. Requirements This board needs a single 30W bench power source adjustable over the input voltage of interest. The loads can either be active (electronic load) or passive (resistor) with the capability to dissipate the maximum load power while keeping accessible surfaces ideally <70°C. It is ideal to have an oscilloscope to view the circuit waveforms, but not essential. For the simplest tests, two voltage meters are required to measure input and output voltages. For efficiency measurements, two voltage and two current meters are required to prevent errors due to measurement inaccuracies. Precautions There is no reverse input protection on this board. Be cautious when connecting the input source to ensure correct polarity is observed. Under extreme loading conditions such as short circuit testing, input transients can be quite large if long test leads are used. In such cases, place a 22µF or 47µF, 6.3V Tantalum capacitor at the VIN terminals to prevent over voltage damage to the IC. Getting Started 1. Connect VIN supply to the input terminals +VIN and GND. With the output of this supply disabled, set its voltage to the desired input test voltage. This supply voltage should be monitored at the test boards input terminals to allow voltage drops in the test cables (and ammeter if used) to be accounted for. An ammeter can be added inline with the +VIN input terminal to accurately measure input current as some power sources current and voltage displays can be misleading. 2. Connect the loads to the output terminals between +VO and GND. Again, this output voltage should be monitored by connecting the voltmeter at the +VO and GND terminals. An ammeter can be added inline with the +VO terminal of the evaluation board to accurately measure the output current. Initially, set the output load to 0A to check that the output is regulating properly prior to loaded tests. 3. Enable the input supply. By default, the output voltage is enabled when the input supply of >2.5V is applied. When this threshold is crossed, the enable pin capacitor (1nF) begins to charge at 1V/µs until it reaches 1.25V where switching begins. To test the Enable functions of the MIC22400, a test point is provided. Ordering Information Part Number MIC22400YML EV Description Evaluation board with the Integrated 4A MIC22400 device Ramp Control is a trademark of Micrel, 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 June 2011 M9999-060711-A Micrel, Inc. Other Features EN/DLY C6 creates a delay set by an internal 1µA source charging to a 1.25V threshold. Using a switch-to-ground (Q1) using “SHDN” to enable the part will exhibit approximately 1.3µs enable delay from “SHDN” going low to the start of switching. Using a pulse generator with a low-impedance output connected to the EN terminal will remove this delay as it defeats the internal 1µA source. MIC22400YML Evaluation Board Power-on-Reset (POR) This is an open-drain connection with an on board pull-up resistor (R3) to VIN. This is only asserted high when the FB pin reaches >90% of its nominal set voltage. This can be used as part of the tracking and sequencing function described in the data sheet. Evaluation Board RC (Ramp Control™) Capacitor The MIC22400 has a nominal 1µA current source/sink to the RC pin. The startup output voltage waveform tracks the voltage on RC. 100% output voltage is represented by 0.7V on RC. The default capacitor on RC (C7) of 10nF therefore sets the ramp up time to approximately 700µs. Feedback resistors The output is set nominally at 1.8V. This can be changed by adjusting the upper or lower resistor in the FB potential dividers. It is recommended that R1 or R2 value should be kept <10k to reduce noise susceptibility and offset currents from creating voltage errors. Therefore, choosing R1<10k: R2 = R1 VREF/(VO – VREF) Where VREF = 0.7V DELAY Adding an external capacitor to this pin allows the Power Good delay to be adjusted to perform as a Power-on Reset (POR). As with the RC pin, this pin has an internal 1µA current source and sink. When VFB reaches 90% of its nominal voltage (~ 630mV) the internal 1µA current source charges the capacitor on this pin (C8) to the rising threshold of 1.25V, at this point, PG is asserted high. When the enable pin is set low, POR is asserted low immediately. However, the internal “DELAY” current sink discharges the capacitor (C8) to 1.25V lower than its starting point, at which point, it enables the RC pin 1µA current sink to begin discharging C7. June 2011 2 M9999-060711-A Micrel, Inc. MIC22400YML Evaluation Board Evaluation Board Performances June 2011 3 M9999-060711-A Micrel, Inc. MIC22400YML Evaluation Board Evaluation Board Schematic Bill of Materials Item C1, C2 Part Number AVX C2012X5R0J226M TDK(2) 06036D225TAAT2A GRM188R7160J225M C1608X5R0J225M GRM188R71H102KA01D C4, C5, C12 C1608C0G1H102J 06035C102KAT2A GRM188R71H103KA01D C6 C7 C9 Capacitor, 2.2µF, 6.3V, X7R, Size 0805 TDK(2) Capacitor, 2.2µF, 6.3V, X5R, Size 0805 Murata(3) TDK Capacitor, 1nF, 50V, COG, Size 0603 (1) AVX 2 Murata(3) Capacitor, 10nF, 50V, X7R, Size 0603 1 Capacitor, 39pF, 50V, Size 0603 1 Capacitor, 390pF, 50V, Size 0603 1 Capacitor, 100pF, 50V, Size 0603 1 AVX Murata(3) TDK(2) (1) AVX Murata(3) 06035A391JAT2A (1) C1608COG1H101J 1 Capacitor, 1nF, 50V, X7R, Size 0603 (2) TDK(2) 06035A101JT2A June 2011 Murata 1608COG1H391J GRM188R71H101JA01 2 Capacitor, 2.2µF, 6.3V, X5R, Size 0805 (3) 06035C103KAT2A GRM188R71H391JA01 C8 AVX(1) (1) 06035A390JAT2A Capacitor, 22µF, 6.3V, X5R, Size 0805 Murata TDK(2) C1608COG1H390J Qty. (3) C1608X7R1H103K GRM188R71H390JA01 Description (1) 08056D226MAT GRM21BR60J226ME39L C3 Manufacturer AVX Murata(3) TDK(2) (1) AVX 4 M9999-060711-A Micrel, Inc. MIC22400YML Evaluation Board Bill of Materials (Continued) Item Part Number GRM31CR60J476ME19 C10, C11 CIN L1 Manufacturer Description Qty. (3) Murata C3216X5R0J476M TDK(2) 12066D476MAT2A (1) AVX B41125A3477M Epcos Capacitor, 47µF, 6.3V, X5R, Size 1206 2 470µF, 10V, Electrolytic, 8x10-case (5) FP3-1R0-R( 7.2x6.7x3mm ) Cooper Inductor, 1µH, 6.26A 1 CDRH8D28NP-1R0NC ( 8x6x3mm ) Sumida(6) Inductor, 1µH, 8A 1 Inductor, 1µH, 12A 1 SPM6530T-1R0M120 ( 7x6.5x3mm ) (2) TDK (4) R1 CRCW06031101FKEYE3 Vishay Resistor, 1.1k, 1%, Size 0603 1 R2 CRCW06036980FKEYE3 Vishay(4) Resistor, 698, 1%, Size 0603 1 R3 CRCW06032002FKEYE3 Vishay(4) Resistor, 20k, 1%, Size 0603 1 R4 CRCW06034752FKEYE3 (4) Vishay Resistor, 47.5k, 1%, Size 0603 1 R5 CRCW06031003FKEYE3 Vishay(4) Resistor, 100k, 1%, Size 0603 1 (4) Resistor, 2.2Ω, 1%, Size 0603 1 (4) Resistor, 49.9Ω, 1%, Size 0603 1 (4) R6 CRCW06032R20FKEA R7 CRCW060349R9FKEA Vishay Vishay Q1 2N7002E Vishay Open 1 U1 MIC22400YML Micrel(7) Integrated 4A Synchronous Buck Regulator 1 Notes: 1. AVX: www.avx.com. 2. TDK: www.tdk.com. 3. Murata: www.murata.com. 4. Vishay: www.vishay.com. 5. Cooper Bussmann: www.cooperet.com. 6. Sumida: www.sumida.com. 1. Micrel, Inc.: www.micrel.com. June 2011 5 M9999-060711-A Micrel, Inc. MIC22400YML Evaluation Board PCB Layout Recommendations Top Silk Top Layer June 2011 6 M9999-060711-A Micrel, Inc. MIC22400YML Evaluation Board PCB Layout Recommendations (Continued) Mid Layer 1 Mid Layer 2 June 2011 7 M9999-060711-A Micrel, Inc. MIC22400YML Evaluation Board PCB Layout Recommendations (Continued) Bottom Silk Bottom Layer June 2011 8 M9999-060711-A Micrel, Inc. MIC22400YML 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 Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. 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. June 2011 9 M9999-060711-A