MIC24056 Evaluation Board 12A, High-Efficiency, Synchronous DC/DC Buck Regulator with HyperLight Load SuperSwitcher II Power-Up Precautions General Description The evaluation board does not have reverse polarity The MIC24056 DC/DC synchronous buck regulator operates protection. Applying a negative voltage to the VIN terminal over an input supply range of 4.5V to 19V and provides a may damage the device. The maximum VIN operating regulated output at up to 12A of load current. The output voltage of the MIC24056 evaluation board is 19V. It has voltage is adjustable down to 0.8V with a typical accuracy of two different layout designs, one (Figure 1) optimized for 1%. evaluation and a second (Figure 2) optimized for a smaller Micrels HyperLight Load architecture maintains high footprint. The evaluation board is only populated with efficiency under light load conditions by transitioning to components shown in Figure 1. variable frequency, discontinuous mode operation. The Hyper Speed Control allows using smaller output Getting Started capacitance. The device operates at a switching frequency of 1. VIN Supply. 600kHz, which remains relatively constant with changes in Connect a supply to the VIN and GND terminals, input voltage and output load. paying careful attention to the polarity and the supply The MIC24056 utilizes an adaptive T ripple control ON range (5V < VIN < 19V). An ammeter may be placed architecture. An undervoltage lockout feature is provided to between the input supply and the VIN terminal to the ensure proper operation under power-sag conditions. An evaluation board. Ensure that the supply voltage is internal soft-start feature is provided to reduce the inrush monitored at the VIN terminal. The ammeter and/or current. Foldback current limit and hiccup mode short-circuit power lead resistance can reduce the voltage supplied protection and thermal shutdown ensures protection of the IC to the input. Do not apply power until Step 4. during fault conditions. 2. Connect the load to the VOUT and ground The HyperLight Load and Hyper Speed Control features terminals. allow ideal transition from light load to full load and vice versa. The 19V operating rating of the device provides ample design The load can be either passive (resistive) or active (as safety margin for 12V input applications. in an electronic load). An ammeter can be placed between the load and the VOUT terminal. Ensure that The basic parameters of the MIC24056 evaluation board are the output voltage is monitored at the VOUT terminal. a VIN supply of 5V to 19V, output voltage of 0.8V to 5V at (1) 3. Enable Input. 12A , and 600kHz switching frequency. An EN connector is provided on the evaluation board Note: 1. Refer to the temperature curves presented in the Evaluation Board for users to easily access the enable feature. The Performance section. Also, note that the typical minimum input output of the MIC24056 turns on when VDD exceeds voltage to maximum output voltage conversion is limited by the the UVLO threshold. The output of the MIC24056 may maximum duty cycle. be turned off by shorting the EN pin to ground. 4. Turn on the power. Datasheets and support documentation are available on Turn on VIN power supply and verify that the output Micrels web site at: www.micrel.com. voltage is regulated to 1.8V. Requirements Ordering Information The MIC24056 evaluation board requires only a single Part Number Description power supply with at least 10A current capability. The MIC24056 has internal VDD LDO so no external linear 12A HLL DC/DC Buck Regulator MIC24056YJL EV regulator is required to power the internal biasing of the IC. Evaluation Board When VIN < 5.5V, VDD should be tied to PVIN pins to bypass the internal linear regulator by a jumper. The output load can either be an active or passive load. HyperLight Load is a registered trademark of Micrel, Inc. Hyper Speed Control, SuperSwitcher II, and Any Capacitor are trademarks 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. MIC24056 Evaluation Board Output Voltage The output voltage on the MIC24056 evaluation board is adjustable. It is set by adjusting the feedback resistors, referring Equation 1: R4 Eq. 1 V = V 1 + OUT FB R BOTTOM where V = 0.8V and R is one of the R5, R6, R7, FB BOTTOM R8, R9, R10, R11, R12 which corresponds to 0.9V, 1.0V, 1.2V, 1.5V, 1.8V, 2.5V, 3.3V, or 5V. Leaving the R BOTTOM open gives a 0.8V output voltage. The output voltage above is set at the factory for a 1.8V output, but it can easily be changed by moving the jumper to a respective position to get an indicated voltage on the board. If a desired voltage is not shown on the board, it is easily modified by removing R and replacing it with the BOTTOM values that yield the desired output voltage. Once R4 is selected, R can be calculated using Equation 2: BOTTOM R4 V FB R = Eq. 2 BOTTOM V V OUT FB For V = 0.8V, as in Equation 3: FB R4 0.8V R = Eq. 3 BOTTOM V 0.8V OUT The output voltage should not be set to exceed 5V due to the 6.3V rating of the output capacitor and limitation on line regulation. Please refer to the Setting the Output Voltage and Ripple Injection subsections in the Application Information section of the MIC24056 datasheet for more detailed information. Revision 1.0 February 11, 2013 2