MIC2174 3A Evaluation Board Constant Frequency, Synchronous Buck Controller Featuring Adaptive On- Time Control TM Hyper Speed Control Family VIN terminal to the evaluation board. Ensure the supply General Description voltage is monitored at the VIN terminal. The ammeter TM MIC2174, a member of the new Hyper Speed Control and/or power lead resistance can reduce the voltage family of buck controllers introduced by Micrel, is a supplied to the input. synchronous, adaptive on-time buck controller. This 2. Connect an external supply to VDD terminal. Apply controller is targeted for cost sensitive applications desired input voltage to the VDD (J6) and ground (J5) requiring high performance. The MIC2174 operates over terminals of the evaluation board, paying careful attention an input supply range of 3V to 40V, and is independent of to polarity and supply voltage (3.0V<VDD<5.5V). The VDD the IC supply voltage. power supply should be turned on no earlier than VIN Data sheets support documentation can be found on power supply. The recommended voltage for VIN is 5V. Micrels web site at www.micrel.com. 3. Connect the load to the VOUT and ground terminals. The load can be either passive (resistive) or active (as in an electronic load). An ammeter can be placed between Requirements the load and the VOUT (J2) terminal. Ensure the output voltage is monitored at the VOUT terminal. The default The MIC2174 evaluation board requires two power VOUT is set to 1.8V. This can be adjusted by changing the supplies: one to provide VIN (connect to HSD pin of feedback resistors. See Output Voltage. MIC2174), and the other to provide VDD (connect to IN pin of the MIC2174) for the control circuitry. The VIN power 4. Enable the MIC2174. The enable pin is floating by supply should be able to deliver greater than 3.0V at over default. The output of the MIC2174 turns on when VDD 3A. The VDD power source, which is recommended to be exceeds the UVLO threshold. The output of the MIC2174 5.0V typical, should be able to deliver greater than 3.0V. may be turned off by shorting the enable pin to ground or The typical VDD current is a few milliamps. An external bringing the enable pin below the enable threshold. An 20mA minimum power supply is recommended for VDD. external connection on the board provides easy access to the enable pin. Precautions Output Voltage The evaluation board does not have reverse polarity The output voltages on the MIC2174 evaluation board are protection. Applying a negative voltage to the VIN or VDD adjustable. The output voltage is controlled by the terminal may damage the device. In addition, the feedback resistors (R4 and R6) and can be calculated as maximum VIN operating voltage of the MIC2174 follows: evaluation board is 40V, and the maximum VDD operation R4 voltage is 5.5V. Exceeding 42V on VIN or exceeding 6V on V = V (1 + ) OUT REF VDD could damage the device. R6 An external VDD power supply is required and it should be where V = 0.8V. REF turned on no earlier than VIN power supply to make sure The evaluation board is preset at a 1.8V output, but can the soft-start behavior properly. easily be modified by removing R6 and replacing it with the Getting Started value that yields the desired output voltage. R4 V 1. Connect an external supply to VIN terminal. Apply REF R6 = desired input voltage to the VIN (J1) and ground (J4) V V OUT REF terminals of the evaluation board, paying careful attention For V = 0.8V, this reduces to: REF to polarity and supply voltage (3.0V<VIN<40V). An ammeter may be placed between the input supply and the Hyper Speed Control is a 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. MIC2164 5A Evaluation Board R4 0 .8V Ordering Information R6 = V 0 .8V OUT Part Number Description Package Ensure the output voltage set does not exceed 5V, since the output capacitor has a 6.3V voltage rating. When the MIC2174-1YMM IC 10-pin MSOP output voltage greater than 5V is desired, the output MIC2174-1YMM Evaluation Board 10-pin MSOP capacitor should be replaced with higher voltage rating. 3A EV December 2009 2 M9999-122309-A