MIC23158/9 Evaluation Board 3MHz, PWM, Dual 2A Buck Regulator with HyperLight Load® and Power Good General Description This board enables the evaluation of the MIC23158, a fully-integrated 2A, 3MHz, dual switching regulators ® featuring HyperLight Load mode, power good output indicator, and programmable soft-start. The MIC23158 is highly efficient throughout the entire output current range, drawing just 45µA of quiescent current for both outputs in ® package, in operation. The 3mm × 4mm MLF combination with the 3MHz switching frequency, enables a compact sub-1mm height solution. The MIC23158 provides accurate output voltage regulation under the most demanding conditions and responds extremely quickly to a load transient with exceptionally small output voltage ripple. Requirements This board requires a single 15W 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 7W. It is ideal to have an oscilloscope available to view the circuit waveforms, but not essential. For the simplest tests, three voltage meters are required to measure input and two output voltages. For efficiency measurements, three voltage meters and three ammeters are required to prevent errors due to measurement inaccuracies. Precautions There is no reverse input protection on this board, therefore caution is advised when connecting the input source to ensure correct polarity is observed. Evaluating the MIC23159YML The MIC23159YML provides an auto discharge feature that switches in a 225Ω pull down circuit on its output to discharge the output capacitor when disabled. The evaluation board can be easily modified by interchanging the MIC23158 device with MIC23159. Getting Started 1. Connect an external supply to the VIN (J1 or J5) and GND terminals. 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 (J1 or J5) terminal. Be sure to monitor the supply voltage at the VIN (J1 or J5) terminal, as the ammeter and/or power lead resistance can reduce the voltage supplied to the device.. 2. Connect a load to the VOUT (J2 and J6) and GND terminals. The load can be either passive (resistive) or active (electronic load). An ammeter may be placed between the load and the output terminals. Ensure the output voltage is monitored at the VOUT (J2 and J6) terminals. 3. Enable the MIC23158 (J9 and J10). The MIC23158 evaluation board has a pull-up resistor 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 0.4V to the EN terminals. 4. Power Good (J11 and J12). A power good test point is provided to monitor the power good function. The power good output will go high approximately 70µs after the output voltage reaches 90% of its nominal voltage. Ordering Information Part Number Description MIC23158YML EV Adjustable Output Evaluation Board (VOUT1 = 1.8V, VOUT2 = 1.5V) Datasheets and support documentation are available on Micrel’s web site at: www.micrel.com. HyperLight Load is a registered 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 February 4, 2013 Revision 1.0 Micrel, Inc. MIC23158/9 Evaluation Board Evaluation Board Some example values are shown in Table 1: Table 1. Feedback Resistor Values for Adjustable Outputs VOUT R4 and R5 R6 and R7 274k 294k 1.5V 316k 221k 1.8V 301k 158k 2.5V 324k 107k 3.3V 309k 71.5k The feed-forward capacitors (C11 and C12) are typically not fitted. The transient performance can be improved slightly by fitting a capacitor at C11 and C12 to inject fast output voltage deviations directly into the feedback comparator. This improved load regulation is 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. Features Soft-Start Capacitors (C9 and C10) The MIC23158 has a nominal 296kΩ resistor charging the capacitor on the SS pin. This enables the output to follow a controlled soft start characteristic. Setting C9 and C10 to 470pF sets the startup time to approximately 320µs. The start-up time can be determined by Equation 1: 3 TSS = 296 × 10 × ln(10) × CSS Power Good (PG) The evaluation board has a test point provided for monitoring the power good feature. This is an open drain connection with an on-board pull-up resistor of 10k to the output voltage. Power good is asserted high approximately 70µs after the output voltage passes 90% of the nominal set voltage. HyperLight Load Mode MIC23158 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 synchronous 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 MIC23158 works in pulse frequency modulation (PFM) to regulate the output. As the output current increases, the off-time decreases, thus providing more energy to the output. This switching scheme improves the efficiency of MIC23158 during light load currents by only switching when it is needed. Eq. 1 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 (R4, R5, R6, and R7) for Adjustable Outputs The output voltages are set nominally to 1.8V and 1.5V. These outputs can be changed by adjusting the upper resistor, R4 and R5, in the feedback potential divider. Therefore: R4 = R6 x (VO−VREF)/VREF R5 = R7 x (VO−VREF)/VREF where VREF = 0.62V. February 4, 2013 1.2V 2 Revision 1.0 Micrel, Inc. MIC23158/9 Evaluation Board As the load current increases, the MIC23158 goes into continuous conduction mode (CCM) and switches at a frequency centered at 3MHz. The equation to calculate the load when the MIC23158 goes into continuous conduction mode may be approximated by Equation 2: ILOAD > (VIN − VOUT ) × D 2L × f Eq. 2 As shown in Equation 2, the load at which MIC23158 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). Refer to the “Switching Frequency vs. Output Current” graph in the Evaluation Board Performance section to see an example of how when the output current increases, the switching frequency also increases until the MIC23158 goes from HyperLight Load mode to PWM mode at approximately 180mA. The MIC23158 will switch at a relatively constant frequency around 3MHz once the output current is over 180mA. February 4, 2013 3 Revision 1.0 Micrel, Inc. MIC23158/9 Evaluation Board Evaluation Board Performance 100 90 90 80 80 VIN = 4.2V 70 VIN = 5V EFFICIENCY (%) 60 50 40 30 20 90 80 70 VIN = 4.2V VIN = 3.6V VIN = 5V 60 50 40 30 COUT=4.7µF L=1µH COUT=4.7µF L=1µH 10 0 10 100 1000 10000 10 100 1000 RISE TIME (µs) EFFICIENCY (%) VIN = 2.7V VIN = 5V VIN = 4.2V 40 COUT=4.7µF L=1µH 10 0 1 10 100 1000 OUTPUT CURRENT (mA) February 4, 2013 10000 100 1000 10000 5.0 10000 1000 100 10 100 10 Switching Frequency vs. Output Current 30 20 COUT=4.7µF L=1µH 1 1000000 VIN = 3.6V 50 30 OUTPUT CURRENT (mA) 100000 60 40 10000 90 70 50 VOUT Rise Time vs. CSS 80 VIN = 5V VIN = 4.2V OUTPUT CURRENT (mA) Efficiency (VOUT = 1.5V) vs. Output Current VIN = 3.6V 0 1 OUTPUT CURRENT (mA) 100 VIN = 2.7V 60 10 0 1 70 20 20 10 Efficiency (VOUT = 1.8V) vs. Output Current 100 VOUT = 1.8V COUT = 4.7µF SWITCHING FREQUENCY (MHz) EFFICIENCY (%) 100 Efficiency (VOUT = 2.5V) vs. Output Current EFFICIENCY (%) Efficiency (VOUT = 3.3V) vs. Output Current 4.5 4.0 L=1.0µH 3.5 3.0 L=0.47µH 2.5 2.0 1.5 1.0 0.5 0.0 1000 10000 CSS (pF) 4 100000 1000000 0.1 1 10 100 1000 10000 OUTPUT CURRENT (mA) Revision 1.0 Micrel, Inc. MIC23158/9 Evaluation Board Evaluation Board Schematic (Adjustable Output) February 4, 2013 5 Revision 1.0 Micrel, Inc. MIC23158/9 Evaluation Board Bill of Materials Item Part Name 06036D475KAT2A C1, C2, C7, C8 C3, C4 C9, C10 C13 L1, L2 R1, R2, R3, R12 R4 R5 R6 R7 R8, R9 R10, R11 U1 GRM188R60J475KE19D Manufacturer (2) TDK AVX Murata TDK AVX Murata TDK LQH44PN1R0NJ0 CRCW06030000Z0EA CRCW06033013FKEA CRCW06033163FKEA CRCW06031583FKEA CRCW06032213FKEA CRCW06031003FKEA CRCW06031002FKEA MIC23158YML 4.7µF, 6.3V, X5R, 0603 4 1µF, 0603, 6.3V 2 470pF, 50V, 0603 2 Cap Alum, 100µF, 50V, 20%, Radial 1 (3) 06036D105KAT2A GRM188R60J105KA01D C1608X5R0J105K 06035A471JAT2A GRM1885C1H471JA01D C1608C0G1H471J CDRH4D28CLDNP-1R0P Qty. AVX Murata C1608X5R0J475K EKY-500ELL101MHB5D Description (1) United Chemi-con Sumida (4) 1µH, 3.0A, 14mΩ, L5.1mm × W5.1mm × H3.0mm (5) Murata Vishay/Dale (6) Vishay/Dale Vishay/Dale Vishay/Dale Vishay/Dale Vishay/Dale Vishay/Dale (7) Micrel, Inc. 1µH, 2.0A, 48mΩ, L4.0mm × W4.0mm × H1.1mm 2 0Ω, 1/10W, 0603 4 301KΩ, 1%, 1/10W, 0603 316KΩ, 1%, 1/10W, 0603 158KΩ, 1%, 1/10W, 0603 221KΩ, 1%, 1/10W, 0603 100KΩ, 1%, 1/10W, 0603 10KΩ, 1%, 1/10W, 0603 3MHz, PWM, Dual 2A Buck Regulator with HyperLight Load and Power Good 1 1 1 1 2 2 1 Notes: 1. AVX: www.avx.com. 2. Murata: www.murata.com. 3. TDK: www.tdk.com. 4. United Chemi-con: www.chemi-con.com. 5. Sumida: www.sumida.com. 6. Vishay: www.vishay.com. 7. Micrel, Inc.: www.micrel.com. February 4, 2013 6 Revision 1.0 Micrel, Inc. MIC23158/9 Evaluation Board PCB Layout Recommendations Top Layer Bottom Layer February 4, 2013 7 Revision 1.0 Micrel, Inc. MIC23158/9 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. © 2013 Micrel, Incorporated. February 4, 2013 8 Revision 1.0 Micrel, Inc. MIC23158/9 Evaluation Board Revision History Date Change Description/Edits by: 02/04/13 Initial draft version reflowed into 2013 template – by S. Thompson February 4, 2013 Rev. 9 1.0 Revision 1.0