MIC33163/4 Evaluation Board 4MHz PWM 1A Buck Regulator with Integrated Inductor and HLL Technology General Description Getting Started The MIC33163/4 evaluation board allows the customer to 1. Connect an external supply to the V (J1) and GND IN evaluate a fully-integrated MOSFETs & Inductor 1A, 4MHz (J2) terminals. synchronous buck regulator that features HyperLight With the output of the power supply disabled, set its Load mode, a Power Good output indicator, and voltage to the desired input test voltage (2.7V V IN programmable soft-start. The MIC33163/4 is highly 5.5V). An ammeter may be placed between the input efficient throughout the output current range. The tiny supply and the V (J1) terminal. Be sure to monitor IN 2.5mm x 3mm QFN package, in combination with the the supply voltage at the V (J1) terminal, as the IN 4MHz switching frequency, provides a compact sub- ammeter and/or power lead resistance can reduce the 1.1mm height solution and 7mm x 4.6mm total solution voltage supplied to the device. size that requires few external components. 2. Connect a load to the V (J3) and GND (J4) OUT The MIC33163/4 has a maximum 100% duty cycle and the terminals. MIC33164 incorporates an active discharge feature. It The load can be either passive (resistive) or active provides accurate output voltage regulation under the most (electronic load). An ammeter may be placed between demanding conditions and responds extremely quickly to a the load and the output terminal. Make sure the output load transient with exceptionally small output voltage voltage is monitored at the V (J3) terminal. OUT ripple. 3. Enable the MIC33163/4. Requirements The MIC33163/4 evaluation board has a pull-up The MIC33163/4 evaluation board requires a single 15W resistor (R3) to V . By default, the output voltage is IN bench power source adjustable from 2.7V to 5.5V. The enabled when the input supply of >2.7V is applied. To loads can either be active (electronic load) or passive disable the device, apply a voltage below 0.5V to the (resistor), and must be able to dissipate 10W. It is ideal, EN (J6) terminal. but not essential, to have an oscilloscope available to view the circuit waveforms. The simplest tests require two 4. Power Good. voltage meters to measure input and output voltages. A PG test point (J5) is provided to monitor the Power Efficiency measurements require two voltage meters and Good feature. The Power Good output will go high two ammeters to prevent errors caused by measurement (V ) approximately 90s after the output voltage OUT inaccuracies. reaches 92% of its nominal voltage. Precautions There is no reverse input protection on this board. Be Ordering Information careful when connecting the input source to ensure correct polarity is observed. Part Number Description Datasheets and support documentation are available on MIC33163YGJ EV MIC33163 Evaluation Board Micrels web site at: www.micrel.com. MIC33164YGJ EV MIC33164 Evaluation Board HyperLight Load is a registered trademark of Micrel, Inc. Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC33163/4 Evaluation Board Table 1. Example Feedback Resistor Values Evaluation Board V R1 R2 OUT 1.2V 215k 301k 1.5V 301k 261k 1.8V 340k 215k 2.5V 274k 107k 3.3V 383k 102k 5V 634k 102k The feed-forward capacitor, C4, provides essential compensation for the MIC33163/4. A typical value range of 15pF to 68pF is recommended. Power Good (PG) The evaluation board has a test point provided for testing the Power Good feature. This is an open-drain connection with an on-board pull-up resistor of 100k to the output voltage. Power Good is asserted high approximately 90s Features after the output voltage passes 92% of the nominal set voltage. Soft-Start Capacitor (C3) The soft start (SS) pin is used to control the output voltage HyperLight Load Mode ramp-up time. Setting C3 to 1nF sets the start-up time to MIC33163/4 uses a minimum on and off time proprietary the minimum. The start-up time can be determined by control loop (patented by Micrel). When the output voltage Equation 1: falls below the regulation threshold, the error comparator begins a switching cycle that turns the PMOS on and 3 T = 250 10 ln(10) C Eq. 1 SS SS keeps it on for the duration of the minimum-on-time. This increases the output voltage. If the output voltage is more than the regulation threshold, then the error comparator The action of the soft-start capacitor is to control the rise turns the PMOS off for a minimum-off-time until the output time of the internal reference voltage between 0% and drops below the threshold. The NMOS acts as an ideal 100% of its nominal steady-state value. rectifier that conducts when the PMOS is off. Using an NMOS switch instead of a diode allows for lower voltage Feedback Resistors (R1, R2) drop across the switching device when the NMOS is on. The output voltage of the evaluation board is set to 2V. The asynchronous switching combination between the This output can be changed by adjusting the upper PMOS and the NMOS allows the control loop to work in resistor, R1, in the feedback potential divider. The output discontinuous mode for light load operations. In voltage can be programmed between 0.7V and 5V using: discontinuous mode, the MIC33163/4 works in pulse frequency modulation (PFM) to regulate the output. As the R1 output current increases, the off-time decreases. This V = V 1 + OUT REF R2 provides more energy to the output. This switching Eq. 2 scheme improves the efficiency of MIC33163/4 during light Where V = 0.7V load currents by only switching when it is needed. REF As the load current increases, the MIC33163/4 goes into continuous conduction mode (CCM) and switches at a frequency centered at 4MHz. Revision 1.0 May 7, 2014 2