MIC22950YML Evaluation Board Integrated 10A Synchronous Buck Regulator General Description The Micrel MIC22950 is a high-efficiency, 10A integrated synchronous buck (step-down) regulator. The MIC22950 is optimized for highest power density and achieves over 90% efficiency while switching at 400kHz to 2MHz. The MIC22950 features integrated 10A MOSFETs, flexible sequencing and tracking abilities. This board enables the evaluation of the MIC22950. The board is optimized for ease of testing, with all the components on a single side. The voltage mode feedback loop is designed to allow high bandwidth with just 2 external compensation components. The high-side MOSFET is a P-Channel, allowing duty-cycle control up to 100%. 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. The MIC22950 offers a full-range of sequencing and tracking options. The EN/DLY pin combined with the PG/POR pin allows multiple outputs to be sequenced in any way on turn-on and turn-off using EN/DLY pin. The RC (Ramp Control™) pin allows the device to be connected to another MIC22950 device to keep the output voltages within a certain delta V on start up. Requirements This board needs a single bench power source adjustable over the input voltage of 2.6V< VIN < 5.5V that can provide at least 10A of current. The load can either be active (electronic load) or passive (resistor) with the ability to dissipate the maximum load power while keeping accessible surfaces ideally < 70°C. Precautions There is no reverse input voltage protection on this board. When connecting an input source, ensure that correct polarity is observed. Under extreme load conditions such as short circuit testing, input transients can be quite large if long test leads are used. In such cases, a 1200µF, 10V Electrolytic capacitor is installed at the VIN terminals to prevent over voltage damage to the IC. Getting Started 1. Connect VIN supply to the input terminals PVIN and PGND. With the output of this supply disabled, set its voltage to the desired input test voltage (2.6V< VIN < 5.5V). 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. 2. Connect the loads to the output terminals between VOUT and PGND. Again, this output voltage should be monitored by connecting the voltmeter at the VOUT and SGND terminals. An ammeter can be added inline with the VOUT terminal of the evaluation board to accurately measure the output current. Output voltage is set to 1.8V. Output voltage can be changed by selecting the resistor R2. The resistor divider network for a desired VOUT is given by: R2 = R1 ⎞ ⎛ VOUT ⎜⎜ − 1⎟⎟ ⎠ ⎝ VREF where VREF is 0.7V and VOUT is the desired output voltage. 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 an input supply of > 2.6V is applied. When this input 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 MIC22950, a test point is provided. Ordering Information Part Number Description MIC22950YML EV Evaluation Board with the Integrated 10A MIC22950 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 December 2009 M9999-122209-A Micrel, Inc. MIC22950 Evaluation Board Other Features DELAY Time Input Adding an external capacitor to this DELAY pin allows the Power Good delay to be adjusted to perform as a PowerOn Reset (POR). As with the RC pin, this pin has an internal 1µA current source and sink. After EN pin voltage is driven high, VOUT will start to rise (rate determined by RC pin capacitor). As the FB pin voltage goes above 90% of its nominal set voltage, DELAY pin voltage begins to rise as the 1µA source charges the external capacitor. When the threshold of 1.24V is crossed, POR/PG pin is asserted high and DELAY pin continues to charge to a voltage SVIN. When FB pin voltage falls below 90% of nominal, POR/PG is asserted low immediately. However, if EN pin is driven low, POR/PG pin voltage will fall immediately to the low state and DELAY pin voltage will begin to fall as the external capacitor is discharged by the 1µA current sink. When the threshold of ((VTP+1.24V)-1.24V) is crossed (VTP is the internal voltage clamp, VTP-=0.9V), VOUT will begin to fall at a rate determined by the RC pin capacitor. As the voltage change in both cases is 1.24V, both rising and falling delays are matched. EN/DLY Input C13 creates a delay set by an internal 1µA source charging to a 1.25V threshold. A switch (Q1) is used from EN pin to ground as shutdown ‘SHDN’ control. 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/DLY terminal will remove this delay as it defeats the internal 1µA source. RC (Ramp Control™) Pin Capacitor The MIC22950 has a nominal 1µA current source/sink to the RC pin. The startup output voltage waveform tracks the voltage on RC pin. 100% output voltage is represented by 0.7V on RC pin. The default capacitor C12, 220pF on RC pin sets the ramp up time to approximately 150µs. 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 = R1xVREF/(VO – VREF) where VREF = 0.7V. December 2009 POR (Power-On Reset) Output This is an open drain connection with an on board pull-up resistor (R4) to PVIN. 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. 2 M9999-122209-A Micrel, Inc. MIC22950YML Evaluation Board Evaluation Board Performances 100 Efficiency vs. Load Current (VOUT=1.8V) 100 95 95 90 VIN = 3.6V EFFICIENCY (%) EFFICIENCY (%) 90 85 VIN = 2.6V 80 75 VIN = 5V 70 85 80 75 70 65 65 60 60 0 December 2009 Efficiency vs. Load Current (VOUT=3.3V) 2 4 6 8 LOAD CURRENT (A) 0 10 2 4 6 8 10 LOAD CURRENT (A) 3 M9999-122209-A Micrel, Inc. MIC22950YML Evaluation Board Evaluation Board Schematic Bill of Materials Item C1, C2, C3, C4 C5 Part Number GRM21BR60J226ME39L C2012X5R0J226K C8 December 2009 TDK(2) AVX(3) GRM188R60J106ME47D muRata C1608X5R0J106K VJ0603Y390KXXMB C7 muRata(1) 08056D226MAT2A 06036D106MAT2A C6 Manufacturer TDK AVX Vitramon(4) 06033A390FAT2A AVX C1608C0G1H390J TDK VJ0603Y101KXAAT Vitramon 06025A101KAT2A AVX C1608C0G1H101J TDK VJ0603Y391KXAAT Vitramon 06035A391JAT2A AVX C1608C0G1H391J TDK 4 Description Qty. Ceramic Capacitor, 22µF, 6.3V, X5R, 0805 4 Ceramic Capacitor, 10µF, 6.3V, X5R, 0603 1 Ceramic Capacitor, 39pF, 25V, X7R, 0603 1 Ceramic Capacitor, 100pF, 50V, 0603 1 Ceramic Capacitor, 390pF, 50V, 0603 1 M9999-122209-A Micrel, Inc. MIC22950YML Evaluation Board Bill of Materials (continued) Item Part Number GRM31CR60J476ME19L C9. C10 Manufacturer muRata C3216X5R0J476M TDK 12066D476MAT2A AVX Description Qty. Ceramic Capacitor, 47µF, 6.3V, 1206 2 C11 C13 VJ0603Y102KXXMB Vitramon Ceramic Capacitor, 1nf, 50V, 0603 1 C14 VJ0603Y103KXXMB Vitramon Ceramic Capacitor, 10nf, 50V, 0603 1 C12 06035A121JAT2A AVX C1608COG1H121J TDK GRM1885C1H121JA01D muRata CIN EEE-FPA122UAP L1 CDEP105ME-1R2MC Sumida(5) 1 1.2µH, 21A , Inductor 1 R1 CRCW06031101FRT1 Vishay Dale(4) Resistor, 1.1k, 1%, 0603 1 R2 CRCW0603698RFRT1 Vishay Dale Resistor, 698Ω, 1%, 0603 1 R3 CRCW06032002FRT1 Vishay Dale Resistor, 20k, 1%, 0603 1 R4 CRCW06034752FRT1 Vishay Dale Resistor, 47.5k 1%, 0603 1 R5 CRCW06031003FRT1 Vishay Dale Resistor, 100k 1%, 0603 1 U1 2N7002E(SOT-23) Panasonic(7) Electrolitic 1200uF, 10V, 10x10.2-Case Q1 Notes: 1. Ceramic Capacitor, 120pF, 50V, COG, 0603 Vishay Corp CMDPM7002A Central Semiconductor(5) MIC22950YML Micrel(6) 1 Signal MOSFET-SOT-236 10A Integrated Switch Synchronous Buck Regulator with Frequency Programmable to 2MHz 1 TDK: www.tdk.com 2. AVX: www.avx.com 3. muRata: www.murata.com 4. Vishay: www.vishay.com 5. Central Semiconductor: www.centralsemi.com 6. Micrel, Inc.: www.micrel.com 7. Panasonic: www.panasonic.com December 2009 5 M9999-122209-A Micrel, Inc. MIC22950YML Evaluation Board PCB Layout Recommendations Top Layer Bottom Layer December 2009 6 M9999-122209-A Micrel, Inc. MIC22950YML Evaluation Board PCB Layout Recommendations (continued) Middle Layer Middle Layer December 2009 7 M9999-122209-A Micrel, Inc. MIC22950YML 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 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. December 2009 8 M9999-122209-A