MIC23150 Evaluation Board 4MHz 2A Buck Regulator with HyperLight Load Getting Started General Description 1. Connect an external supply to the V (J1) IN The MIC23150 is a 2A 4MHz switching regulator featuring terminal. Apply the desired input voltage to V IN HyperLight Load mode. The MIC23150 is highly efficient (J1) and ground (J2) terminals of the evaluation throughout the entire output current range, drawing just board, paying careful attention to polarity and 23A of quiescent current in operation. The tiny 2mm x supply voltage (2.7V V 5.5V). An ammeter IN 2mm MLF package, in combination with the 4MHz may be placed between the input supply and the switching frequency, enables a compact sub-1mm height V (J1) terminal. Be sure to monitor the supply IN solution with only three external components. The voltage at the V (J1) terminal, since the ammeter IN MIC23150 provides accurate output voltage regulation and/or power lead resistance can reduce the under the most demanding conditions and responds voltage supplied to the device. extremely quickly to a load transient with exceptionally small output voltage ripple. 2. Connect a load to the V (J3) and ground OUT Factoring in the output current, the internal circuitry of the terminal (J4). The load can be either passive MIC23150 automatically selects between two modes of (resistive) or active (electronic load). An ammeter operation for optimum efficiency. Under light load may be placed between the load and the output conditions, the MIC23150 goes into HyperLight Load terminal. Ensure the output voltage is monitored at mode. HyperLight Load uses a Pulse-Frequency the V (J3) terminal. OUT Modulation (PFM) control scheme that controls the off time 3. Enable the MIC23150. The MIC23150 evaluation at light load. This proprietary architecture reduces the board has a pull-up resistor to V . To disable the amount of switching needed at light load, thereby IN device, apply a voltage below 0.5V to the EN (J5) increasing operating efficiency. The MIC23150 attains up terminal. In the absence of the pull-up resistor, the to 87% efficiency at 1mA output load. As the load current device is enabled by applying a voltage greater increases beyond approximately 100mA, the device than 1.2V to the EN (J5) terminal. The enable pin operates using the Pulse-Width Modulation (PWM) method must be either pulled high or low for proper for up to 93% efficiency at higher load. The two modes of operation. Removing the pull-up resistor and operation ensure the highest efficiency across the entire leaving the pin floating will cause the regulator to load range. operate in an unknown state. The MIC23150 operates from an input voltage range of 2.7V to 5.5V and features internal power MOSFETs that Output Voltage deliver up to 2A of output current. This step-down regulator The MIC23150 evaluation board is available with the provides an output voltage accuracy of +/-2.5% across the following output voltage options listed below: junction temperature range of -40C to +125C. The MIC23150 is available in fixed output versions supporting an output voltage as low as 1.0V. Ordering Information (2) Requirements Part Number Description (1) The MIC23150 evaluation board requires an input power MIC23150-CYMT EV 1.0V Fixed Output Evaluation Board source that is able to deliver greater than 2A at 2.7V to the (1) MIC23150-4YMT EV 1.2V Fixed Output Evaluation Board MIC23150. The output load can either be an active MIC23150-GYMT EV 1.8V Fixed Output Evaluation Board (electronic) or passive (resistive) load. MIC23150-SYMT EV 3.3V Fixed Output Evaluation Board Note: 1. Contact Micrel Marketing 2. Other voltage options available on request. Contact Micrel. HyperLight Load is a trademark of Micrel, Inc. MLF is a registered trademark of Amkor Technology. Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC23150 Evaluation Board As shown in the previous equation, the load at which HyperLight Load Mode MIC23150 transitions from HyperLight Load mode to MIC23150 uses a minimum on and off time proprietary PWM mode is a function of the input voltage (V ), output IN control loop (patented by Micrel). When the output voltage voltage (V ), duty cycle (D), inductance (L) and OUT falls below the regulation threshold, the error comparator frequency (f). As shown in Figure 1, as the Output Current begins a switching cycle that turns the PMOS on and increases, the switching frequency also increases until the TM keeps it on for the duration of the minimum-on-time. This MIC23150 goes from HyperLight Load mode to PWM increases the output voltage. If the output voltage is over mode at approximately 120mA. The MIC23150 will switch the regulation threshold, then the error comparator turns at a relatively constant frequency around 4MHz once the the PMOS off for a minimum-off-time until the output drops output current is over 120mA. below the threshold. The NMOS acts as an ideal rectifier that conducts when the PMOS is off. Using a NMOS SW Frequency switch instead of a diode allows for lower voltage drop vs Output Current across the switching device when it is on. The 10 asynchronous switching combination between the PMOS V = 3.0V and the NMOS allows the control loop to work in IN V = 3.6V 1 IN discontinuous mode for light load operations. In discontinuous mode, the MIC23150 works in pulse V = 4.2V IN frequency modulation (PFM) to regulate the output. As the 0.1 output current increases, the off-time decreases, thus provides more energy to the output. This switching L = 4.7H 0.01 scheme improves the efficiency of MIC23150 during light V = 1.8V OUT load currents by only switching when it is needed. As the C = 4.7F OUT 0.001 load current increases, the MIC23150 goes into 1 10 100 1000 10000 continuous conduction mode (CCM) and switches at a OUTPUT CURRENT (mA) frequency centered at 4MHz. The equation to calculate the load when the MIC23150 goes into continuous conduction mode may be approximated by the following formula: Figure 1. SW Frequency vs. Output Current (V -V )D IN OUT I > LOAD 2Lf M9999-081709-A August 2009 2 SW FREQUENCY (MHz)