MIC23051 Evaluation Board 4MHz PWM Buck Regulator with HyperLight Load™ and Voltage Scaling General Description Micrel’s MIC23051 is a 600mA 4MHz switching regulator with HyperLight Load™ mode. The MIC23051 is highly efficient throughout the load range and only draws 20μA of quiescent current. Sub-1mm solution is easily obtainable using the tiny package (2mm x 2mm x 0.85mm) MIC23051, which only requires four external components. Small and fast, the MIC23051 can respond to a load transient at ultra-fast speed while reducing output peak-topeak voltage. The MIC23051 also features a voltage scaling function that can be used to set the output voltage to two different voltage levels. The MIC23051 has two modes of operation which is automatically selected by the internal circuitry. Under light load conditions from 1mA to 50mA, the MIC23051 goes into HyperLight Load™ mode. The MIC23051 HyperLight Load™ uses a Pulse-Frequency Modulation (PFM) control scheme that controls the off time at light load and keeps constant switching frequency in continuous mode. This allows the device to reduce the amount of switching needed at light loads, thus reducing the switching losses. The MIC23051 can attain 85% efficiency at 1mA output load. When the load is more than 50mA, HyperLight Load automatically switches back to Pulse-Width Modulation (PWM) mode to ensure high efficiency at higher loads. The two modes of operation ensure that the MIC23051 maintains the highest efficiency throughout the load range. The MIC23051 features Voltage Scaling via the VSC pin. This function allows the MIC23051 to alternate between two different voltage levels. A high input logic on the VSC pin will cause the MIC23051 to regulate at the higher voltage level, while a low input logic will set the MIC23051 to regulate at the lower voltage level. The MIC23051 operates from a 2.7V to 5.5V input and features internal power MOSFETs that can supply up to 600mA of output current. It can operate with a maximum duty cycle of 80%. Requirements The MIC23051 evaluation board requires an input power source that is able to deliver greater than 650mA at 2.7V. The output load can either be an active or passive source. Getting Started 1. Connect an external supply to the VIN (J1) terminal. Apply desired input voltage to the VIN (J1) and ground (J2 and J4) terminals of the evaluation board, paying careful attention to polarity and supply voltage (2.7V ≤ VIN ≤ 5.5V). An ammeter may be placed between the input supply and the VIN (J1) terminal to the evaluation board. Be sure to monitor that the supply voltage at the VIN (J1) terminal. The ammeter and/or power lead resistance can reduce the voltage supplied to the input. 2. Connect a load to the VO (J3) output and ground terminal. The load can be either passive (resistive) or active (electronic load). An ammeter can be placed between the load and the output terminal. Ensure that the output voltage is monitored at the Vo (J3) terminal. 3. Scale the output voltage. Connect the VSC (J6) pin to VIN (J1) to scale the output voltage to the higher voltage. Connect the VSC (J6) pin to GND (J2) to scale the output voltage to the lower voltage. Do not leave floating. 4. Enable the MIC23051. Apply a 1.2V or greater voltage source to the enable pin (EN). Be sure that the enable voltage never exceeds the input voltage. Do not leave floating. Output Voltage The MIC23051 evaluation board has fixed voltage options (1.2V/1V and 1.8V/1V) available. Ordering Information Part Number Description MIC23051-C4YML EV 1.2V / 1V Output Evaluation Board MIC23051-CGYML EV 1.8V / 1V Output Evaluation Board HyperLight Load 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 November 2008 M9999-112008-B Micrel, Inc. HyperLight Load™ Mode MIC23051 uses a minimum on and off time proprietary control loop. When the output voltage falls below the regulation threshold, the error comparator begins a switching cycle that turns the PMOS on and keeps it on for the duration of the minimum-on-time. When the output voltage is over the regulation threshold, the error comparator turns the PMOS off for a minimum-off-time. The NMOS acts as an ideal rectifier that conducts when the PMOS is off. Using a NMOS switch instead of a diode allows for lower voltage drop across the switching device when it is on. The asynchronous switching combination between the PMOS and the NMOS allows the control loop to work in discontinuous mode for light load operations. In November 2008 MIC23051 Evaluation Board discontinuous mode MIC23051 works in pulse frequency modulation (PFM) to regulate the output. As the output current increases, the switching frequency increases. This improves the efficiency of MIC23051 during light load currents. As the load current increases, the MIC23051 goes into continuous conduction mode (CCM) at a constant frequency of 4MHz. The equation to calculate the load when the MIC23051 goes into continuous conduction mode may be approximated by the following formula: ⎛ (V − VOUT ) × D ⎞ ILOAD = ⎜ IN ⎟ 2L × f ⎝ ⎠ 2 M9999-112008-B Micrel, Inc. MIC23051 Evaluation Board MIC23051 Evaluation Board Schematic Bill of Materials Item Part Number Manufacturer (1) Description Qty C1, C2 C1608X5R0J476K TDK 4.7µF Ceramic Capacitor, 6.3V, X5R, Size 0603 2 C3 C1608C0G1H561J TDK(1) 560pF Ceramic Capacitor, 50V, NPO, Size 0603 1 LQM21PN1R0MC0D LQH32CN1R0M33 L1 LQM31PN1R0M00 CPL2512T1R0M LQM31PNR47M00 MIPF2520D1R5 R1, R2 U1 CRCW06031003FKEYE3 MIC23051-xxYML Murata(2) 1µH, 0.8A, 190mΩ, L2mm x W1.25mm x H0.5mm (2) Murata 1µH, 1A, 60mΩ, L3.2mm x W2.5mm x H2.0mm (2) Murata 1µH, 1.2A, 120mΩ, L3.2mm x W1.6mm x H0.95mm TDK(1) Murata(2) FDK 0.47µH, 1.4A, 80mΩ, L3.2mm x W1.6mm x H0.85mm (3) 1.5µH, 1.5A, 70mΩ, L2.5mm x W2mm x H1.0mm Vishay(4) Micrel, Inc. 1 1µH, 1.5A, 100mΩ, L2.5mm x W1.5mm x H1.2mm (5) 100kΩ, 1%, 1/16W, Size 0603 2 4MHz PWM Buck Regulator with HyperLight Load™ Mode 1 Notes: 1. TDK: www.tdk.com 2. Murata: www.murata.com 3. FDK: www.fdk.co.jp 4. Vishay: www.vishay.com 5. Micrel, Inc: www.micrel.com November 2008 3 M9999-112008-B Micrel, Inc. MIC23051 Evaluation Board PCB Layout Recommendations Top Layer Bottom Layer November 2008 4 M9999-112008-B Micrel, Inc. MIC23051 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. © 2007 Micrel, Incorporated. November 2008 5 M9999-112008-B