MIC24054 Evaluation Board 9A, 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 MIC24054 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 9A of load current. The output voltage of the MIC24054 evaluation board is 19V. The voltage is adjustable down to 0.8V with a typical accuracy of evaluation board has two different layout designs, one 1%. optimized for evaluation (Figure 1) and another one Micrels HyperLight Load architecture maintains high optimized for smaller footprint (Figure 2). The evaluation efficiency under light load conditions by transitioning to board is only populated with components shown in variable frequency, discontinuous mode operation. The schematic Figure 1. Hyper Speed Control allows smaller output capacitance. The device operates at a switching frequency of 600kHz, Getting Started which remains relatively constant with changes in input 1. VIN Supply. voltage and output load. Connect a supply to the VIN and GND terminals, The MIC24054 uses an adaptive T ripple control ON paying careful attention to the polarity and the supply architecture. An undervoltage lockout feature is provided to range (5V < VIN < 19V). An ammeter may be placed ensure proper operation under power-sag conditions. An between the input supply and the VIN terminal to the internal soft-start feature is provided to reduce the inrush evaluation board. Make sure that the supply voltage is current. Foldback current limit and hiccup mode short-circuit monitored at the VIN terminal. The ammeter and/or protection, and thermal shutdown ensures protection of the power lead resistance can reduce the voltage supplied IC during fault conditions. to the input. Do not apply power until Step 4. The HyperLight Load and Hyper Speed Control features 2. Connect the load to the V and ground terminals. OUT allow ideal transition from light load to full load and vice versa. The load can be either passive (resistive) or active (as The 19V operating rating of the device provides ample design in an electronic load). An ammeter can be placed safety margin for 12V input applications. between the load and the V terminal. Make sure OUT The basic parameters of the MIC24051 evaluation board that the output voltage is monitored at the V OUT are a VIN supply of 5V to 19V, output voltage of 0.8V to 5V terminal. (1) at 6A , and 600kHz switching frequency. 3. Enable Input. Note: An EN connector is provided on the evaluation board 1. Refer to the temperature curves shown in Evaluation Board so that users can easily access the enable feature. Performance. The typical minimum input voltage to maximum output The output of the MIC24054 turns on when VDD voltage conversion is limited by the maximum duty cycle. exceeds the UVLO threshold. The output of the MIC24054 may be turned off by shorting the EN pin to ground. Datasheets and support documentation are available on Micrels web site at: www.micrel.com. 4. Turn on the Power. Turn on VIN power supply and verify that the output Requirements voltage is regulated to 1.8V. The MIC24054 evaluation board requires only a single power supply with at least 10A current capability. The Ordering Information MIC24054 has internal VDD LDO so no external linear regulator is required to power the internal biasing of the IC. Part Number Description When VIN < 5.5V, VDD should be tied to PVIN pins to 9A HLL DC/DC Buck Regulator MIC24054YJL EV bypass the internal linear regulator by a jumper. The Evaluation Board output load can be either active or passive. 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. MIC24054 Evaluation Board Output Voltage The output voltage on the MIC24054 evaluation board is adjustable. It is set by adjusting the feedback resistors, as shown in 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, respectively. Leaving R open gives a 0.8V output voltage. The output BOTTOM voltage is set at the factory for a 1.8V output, but it can easily be changed by moving the jumper to the corresponding position to get an indicated voltage on the board. If a desired voltage is not shown on the board, it is easily changed by removing R and replacing it with BOTTOM the values that yield the desired output voltage. After 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: FB R4 0.8V R = Eq. 3 BOTTOM V 0.8V OUT Do not set the output voltage to exceed 5V because of the 6.3V rating of the output capacitor and the limitation of the line regulation. Please refer to the Setting Output Voltage and Ripple Injection subsections of the Application Information section of the MIC24054 datasheet for detailed information. Revision 1.1 February 11, 2013 2