MIC33030 Evaluation Board 8MHz Internal Inductor, 400mA Buck Regulator with HyperLight Load Getting Started General Description 1. Connect an external supply to the V IN This evaluation board enables the evaluation of the terminal and GND. With the output of the power MIC33030, a fully-integrated 400mA, 8MHz switching supply disabled, set its voltage to the desired regulator featuring an internal inductor and HyperLight input test voltage (2.7V V 5.5V). An IN Load mode. The MIC33030 is efficient throughout the ammeter may be placed between the input entire output current range, drawing just 20 A of supply and the V terminal. Be sure to monitor IN quiescent current in operation. The tiny 2.0mm x 2.5mm the supply voltage at the V terminal, as the IN MLF package, in combination with the internal inductor, ammeter and/or power lead resistance can enables a compact solution with only two external reduce the voltage supplied to the device. components. The MIC33030 provides accurate output 2. Connect a load to the V and GND OUT voltage regulation under the most demanding conditions terminals. The load can be either passive and responds extremely quickly to a load transient with (resistive) or active (electronic load). An exceptionally small output voltage ripple. ammeter may be placed between the load and Requirements the output terminal. Ensure the output voltage is monitored at the V terminal. OUT This board needs a single 2W bench power source adjustable from 2.7V to 5.5V. The loads can either be 3. Enable the MIC33030. The MIC33030 active (electronic load) or passive (resistor) with the evaluation board has a pull-up resistor to V . By IN capability to dissipate 1W. It is ideal to have an default, the output voltage will be enabled when oscilloscope available to view the circuit waveforms, but the input supply of 2.7V is applied. To disable not essential. For the simplest tests, two voltage meters the device, apply a voltage below 0.5V to the EN are required to measure input and output voltage. For terminal or jumper the EN terminal-to-GND. efficiency measurements, two Voltage meters and two Ammeters are required to prevent errors due to Ordering Information measurement inaccuracies. Part Number Description Precautions MIC33030 Internal Inductor Buck There is no reverse input protection on this board. Be MIC33030-AYHJ Regulator, Adjustable Evaluation Board cautious when connecting the input source to ensure correct polarity is observed. MIC33030 Internal Inductor Buck MIC33030-4YHJ Regulator, V =1.2V Evaluation Board OUT HyperLight Load is a trademark of Micrel, Inc. MLF and MicroLeadFrame are registered trademark Amkor Technology Inc. Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC33030 Evaluation Board HyperLight Load Mode Evaluation Board The MIC33030 uses a minimum on and off time proprietary control loop (patented by Micrel). 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. This increases the output voltage. If the output voltage is over the regulation threshold, then the error comparator turns the PMOS off for a minimum- off-time until the output drops below the threshold. 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 discontinuous mode, the MIC33030 works in pulse frequency modulation (PFM) to regulate the output. As the output current increases, the off-time decreases, thus provides more energy to the output. This switching scheme improves the efficiency of MIC33030 during light load currents by only switching when it is needed. As the load current increases, the MIC33030 goes into continuous conduction mode (CCM) and switches at a frequency centered at 8MHz. The load current at which the MIC33030 goes into continuous Other Features conduction mode may be approximated to 150mA. Feedback Resistors (R2, R3) for Adjustable Output The output voltage is set nominally to 1.8V. This output can be changed by adjusting the upper resistor (R2) in the feedback potential divider. Therefore: R2 = R3*(V -V )/V O REF REF Where V = 0.62V REF Some example values are: V R2 R3 OUT 1.2V 274k 294k 1.5V 316k 221k 1.8V 301k 158k 2.5V 324k 107k 3.3V 309k 71.5k The Feed-forward capacitor (C3) is typically not fitted since transient load regulation is already very good. However, it can be improved slightly by fitting a capacitor at C3 to inject fast output voltage deviations directly into the feedback comparator. This improved load regulation is at the expense of slightly increasing the amount of noise on the output at higher loads. Values between 100pF and 1nF are recommended to prevent instability. M9999-011211-A January 2011 2