MIC33153-4YHJ-EV

MIC33153 Evaluation Board 4MHz 1.2A PWM Buck Regulator with HyperLight Load™ and Power Good General Description Getting Started This board enables the evaluation of the MIC33153, a fully integrated 1.2A, 4MHz switching regulator featuring HyperLight Load™ mode, Power Good (PG) output indicator, and programmable soft start. The MIC33153 is highly efficient throughout the entire output current range, drawing just 22µA of quiescent current in operation. The tiny 3.5mm x 3.0mm x 0.9mm MLF® package, in combination with the 4MHz switching frequency, enables a compact sub 1mm height solution with only two external input and output capacitors. The MIC33153 provides accurate output voltage regulation under the most demanding conditions and responds extremely quickly to a load transient with exceptionally small output voltage ripple. Datasheets and support documentation can be found on Micrel’s web site at: www.micrel.com. 1. Connect an external supply to the VIN (TP4) terminal and GND (TP3). With the output of the power supply disabled, set its voltage to the desired input test voltage (2.7V ≤ VIN ≤ 5.5V). An ammeter may be placed between the input supply and the VIN (TP4) terminal. Be sure to monitor the supply voltage at the VIN (TP4) terminal, as the ammeter and/or power lead resistance can reduce the voltage supplied to the device. 2. Connect a load to the VOUT (TP1) and ground (TP 2) terminals. The load can be either active passive (resistive) or active (electronic load). An ammeter may be placed between the load and the output terminal. Ensure the output voltage is monitored at the VOUT (TP1) terminal. 3. Enable the MIC33153. The MIC33153 evaluation board has a pull up resistor (R4) to VIN. By default, the output voltage will be enabled when the input supply of >2.7V is applied. To disable the device, apply a voltage below 0.5V to the EN (TP6) terminal. 4. Power Good (PG). A PG test point (TP5) is provided to monitor the Power Good function. The PG output will go high (VOUT) approximately 70µs after the output voltage reaches 92% of its nominal voltage. Requirements This board needs a single 5W bench power source adjustable from 2.7V to 5.5V. The loads can either be active (electronic load) or passive (resistor) with the capability to dissipate 5W. It is ideal to have an oscilloscope available to view the circuit waveforms, but not essential. For the simplest tests two voltage meters are required to measure input and output voltage. For efficiency measurements two voltage meters and two ammeters are required to prevent errors due to measurement inaccuracies. Precautions There is no reverse input protection on this board. Be cautious when connecting the input source to ensure correct polarity is observed. Ordering Information Part Number Description MIC33153-4YHJ 1.2V Fixed Output Evaluation Board MIC33153YHJ Adjustable Output Evaluation Board HyperLight Load is a trademark of Micrel, Inc. MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc. Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com December 2010 M9999-121710-A Micrel, Inc. MIC33153 Evaluation Board Soft start Capacitor The MIC33153 has a nominal 270kΩ resistor charging the capacitor on the SS pin. This enables the output to follow a controlled soft start characteristic. Setting C3 to 100pF sets the startup time to the minimum. The startup time can be determined by: TSS = 270 x 103 x ln(10) x CSS The action of the soft start capacitor is to control the rise time of the internal reference voltage between 0% and 100% of its nominal steady state value. Feedback Resistors (R1, R2) for Adjustable Output The output voltage is set nominally to 1.8V. This output can be changed by adjusting the upper resistor, R1, in the feedback potential divider. Therefore: R1 = R2 × VREF/(VO − VREF) where VREF = 0.62V. Some example values are: VOUT R1 R2 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, C4, is typically not fitted given that transient load regulation is already very good. However, it can be improved slightly by fitting a capacitor at C4 to inject fast output voltage deviations directly into the feedback comparator. This improved load regulation occurs 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. December 2010 Power Good (PG) The evaluation board has a test point provided to the right of EN for testing PG. This is an open drain connection with an on board pull up resistor of 10k to the output voltage. This is asserted high approximately 70µs after the output voltage passes 92% of the nominal set voltage. HyperLight Load™ Mode The MIC33153 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 MIC33153 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 MIC33153 during light load currents by only switching when it is needed. As the load current increases, the MIC33153 goes into continuous conduction mode (CCM) and switches at a frequency centered at 4MHz. The equation to calculate the load when the MIC33153 goes into continuous conduction mode may be approximated by the following formula: VOUT ) × D 2L × f As shown in the above equation, the load at which MIC33153 transitions from HyperLight Load™ mode to PWM mode is a function of the input voltage (VIN), output voltage (VOUT), duty cycle (D), inductance (L) and frequency (f). For example, if VIN = 3.6V, VOUT = 1.8V, D = 0.5, f = 4MHz and the internal inductance of MIC33153 is 0.47μH, then the device will enter HyperLight Load™ mode or PWM mode at approximately 200mA. ILOAD > 2 (VIN M9999-121710-A Micrel, Inc. MIC33153 Evaluation Board MIC33153-xYMT Evaluation Board Schematic (Fixed Output) Bill of Materials Item Part Number C3 R3, R4 C1608X5R0J475K GRM188R60J475KE19D C1608NPO0J471K CRCW06031002FKEA U1 MIC33153-xYHJ C1, C2 Manufacturer TDK(1) Murata(2) TDK(1) Vishay(3) Micrel, Inc.(4) Description Qty. Ceramic Capacitor, 4.7µF, 6.3V, X5R, Size 0603 2 Ceramic Capacitor, 470pF, 6.3V, NPO, Size 0603 Resistor, 10k, Size 0603 1 2 4MHz 1.2A Buck Regulator with HyperLight Load™ Mode and Fixed Output Voltage 1 Notes: 1. TDK: www.tdk.com. 2. Murata: www.murata.com. 3. Vishay: www.vishay.com. 4. Micrel, Inc.: www.micrel.com. December 2010 3 M9999-121710-A Micrel, Inc. MIC33153 Evaluation Board MIC33153 Evaluation Board Schematic (Adjustable Output) Bill of Materials Item Part Number C1, C2 C1608X5R0J475K GRM188R60J475KE19D C3 C1608NPO0J471K C4 R1 R2 R3, R4 − CRCW06033013FKEA CRCW06031583FKEA CRCW06031002FKEA U1 MIC33153-YHJ Manufacturer TDK(1) Murata(2) TDK(1) − Vishay(3) Vishay(3) Vishay(3) Micrel, Inc.(4) Description Qty. Ceramic Capacitor, 4.7µF, 6.3V, X5R, Size 0603 2 Ceramic Capacitor, 470pF, 6.3V, NPO, Size 0603 1 Not Fitted (NF) Resistor, 301k, Size 0603 Resistor, 158k, Size 0603 Resistor, 10k, Size 0603 0 1 1 2 4MHz 1.2A Buck Regulator with HyperLight Load™ Mode and Adjustable Output Voltage 1 Notes: 1. TDK: www.tdk.com. 2. Murata: www.murata.com. 3. Vishay: www.vishay.com. 4. Micrel, Inc.: www.micrel.com. December 2010 4 M9999-121710-A Micrel, Inc. MIC33153 Evaluation Board PCB Layout Recommendations Top Layer Bottom Layer December 2010 5 M9999-121710-A Micrel, Inc. MIC33153 Evaluation Board MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2010 Micrel, Incorporated. December 2010 6 M9999-121710-A