MIC4930 Hyper Speed Control™ 3A Buck Regulator General Description The MIC4930 is a high-efficiency, 3A synchronous buck regulator with ultra-fast transient response perfectly suited for supplying processor core and I/O voltages from a 5V or 3.3V bus. The MIC4930 provides a switching frequency up to 3.3MHz while achieving peak efficiencies up to 95%. An additional benefit of high-frequency operation is very low output ripple voltage throughout the entire load range with the use of a small output capacitor. The MIC4930 is designed for use with a very small inductor, down to 1µH, and an output ceramic capacitor as small as 10µF without the need for external ripple injection. A wide range of output capacitor types and values can also be accommodated. The MIC4930 supports safe start-up into a pre-biased output. The MIC4930 is available in a 10-pin 3mm × 4mm DFN package with an operating junction temperature range from –40°C to +125°C. The MIC4930 is pin-to-pin compatible with the 5A-rated MIC4950YFL. Datasheets and support documentation are available on Micrel’s web site at: www.micrel.com. Features Input voltage: 2.7V to 5.5V 3A output current Up to 95% efficiency Up to 3.3MHz operation Safe start-up into a pre-biased output Power Good output Ultra-fast transient response Low output voltage ripple Low RDS(ON) integrated MOSFET switches 0.01µA shutdown current Thermal shutdown and current limit protection Output voltage as low as 0.7V 3mm × 4mm DFN-10L –40C to +125C junction temperature range Applications DTVs Set-top boxes Printers DVD players Distributed power supplies Typical Application 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 • http://www.micrel.com March 20, 2014 Revision 1.1 Micrel, Inc. MIC4930 Ordering Information Part Number (1) MIC4930YFL Top Mark Temperature Range MIC4930 –40°C ≤ TJ ≤ +125°C Package (2) 10-pin 3mm × 4mm DFN Lead Finish Pb-Free Note: 1. Other options are available. Contact Micrel for details. 2. DFN is a GREEN, RoHS-compliant package. Lead finish is NiPdAu. Mold compound is Halogen free. Pin Configuration 3mm × 4mm DFN (FL) (Top View) Pin Description Pin Number Pin Name Pin Function 1, 2, EP PGND Power ground. 3, 8 PVIN Power input voltage: Connect a 10µF ceramic capacitor between PVIN and PGND for input decoupling. Pins 3 and 8 are internally connected inside the package. 4 AVIN Analog input voltage: Connect a 1µF ceramic capacitor between AVIN and AGND to decouple the noise for the internal reference and error comparator. 5 AGND Analog ground input: Connect to a quiet ground plane for best operation. Do not route power switching currents on the AGND net. Connect AGND and PGND nets together at a single point. 6 FB Feedback (input): Connect an external divider between VOUT and AGND to program the output voltage. 7 PG Power Good (output): Open-drain output. A pull-up resistor from this pin to a voltage source is required to detect an output power-is-good condition. 9 EN Enable (input): Logic high enables operation of the regulator. Logic low will shut down the device. Do not leave floating. 10 SW Switch (output): Internal power MOSFET output switches. March 20, 2014 2 Revision 1.1 Micrel, Inc. MIC4930 Absolute Maximum Ratings(3) Operating Ratings(4) PVIN, AVIN Supply Voltage (VIN) .................... –0.3V to +6V SW Output Switch Voltage (VSW). ..................... –0.3V to VIN EN, PG (VEN, VPG) ............................................. –0.3V to VIN FB Feedback Input Voltage (VFB) ...................... –0.3V to VIN Storage Temperature (Ts)......................... –65°C to +150°C (5) ESD Rating ........................................................ 2kV, HBM Supply Voltage (VIN) ..................................... +2.7V to +5.5V Enable Input Voltage (VEN) ..................................... 0V to VIN Junction Temperature Range (TJ).......–40°C ≤ TJ ≤ +125°C Thermal Resistance DFN-10 (JA) ...................................................... 35°C/W Electrical Characteristics(6) VIN = VEN = 3.3V; L = 1.0µH; TA = 25°C, CIN = 10µH, COUT = 10µH unless otherwise specified. Bold values indicate –40°C≤ TJ ≤ +85°C, unless otherwise noted. Symbol Parameter VIN Supply voltage range VUVLO Undervoltage lockout threshold VUVLOH Undervoltage lockout hysteresis IQ Quiescent current IOUT = 0mA, FB >1.2 × VFB(Nominal) 0.8 2 mA ISD Shutdown current VEN = 0V 0.01 2 µA VFB Feedback voltage 0.609 0.625 0.640 V ILIMIT Current limit 3.5 5.75 8 A LINEREG Output voltage line regulation Condition Min. 2.7 2.41 (turn-on) Output voltage load regulation FB = 0.9V × VFB(Nominal) VIN = 2.7V to 3.5V, VOUTNOM = 1.8V, ILOAD = 20mA VIN = 4.5V to 5.5V if VOUTNOM ≥2.5V, ILOAD = 20mA 20mA < ILOAD < 500mA, VIN = 5.0V if VOUTNOM ≥ 2.5V 20mA < ILOAD < 3A, VIN = 3.6V if VOUTNOM < 2.5V 20mA < ILOAD < 3mA, VIN = 5.0V if VOUTNOM ≥ 2.5V RDSON-P RDSON-N PWM switch ON resistance March 20, 2014 2.5 Max. Units 5.5 V 2.61 V 400 20mA < ILOAD < 500mA, VIN = 3.6V if VOUTNOM < 2.5V LOADREG Typ. 1 %/V 0.3 % 1 % ISW = 1A P-Channel MOSFET 30 ISW = 1A N-Channel MOSFET 25 3 mV mΩ Revision 1.1 Micrel, Inc. MIC4930 Electrical Characteristics Continued(6) VIN = VEN = 3.3V; L = 1.0µH; TA = 25°C, CIN = 10µH, COUT = 10µH unless otherwise specified. Bold values indicate –40°C≤ TJ ≤ +85°C, unless otherwise noted. Symbol tON Parameter Maximum turn-on time Condition Min. Typ. VIN = 4.5V, VFB = 0.5V 665 VIN = 3.0V, VFB = 0.5V 1000 VIN = 2.7V, VFB = 0.5V 1120 Max. Units ns tOFF Minimum turn-off time VIN = 3.0V, VFB = 0.5V 176 ns tSOFT-ON Soft-start time VOUT = 90% of VOUTNOM 500 µs VEN Enable threshold Turn-on 0.5 IEN Enable input current Rising 82 1.2 V 0.1 1 µA 88 94 % 0.8 VOUTPG Power Good threshold VOUTPGH Power Good hysteresis 7 % TSD Overtemperature shutdown 150 °C TSDH Overtemperature shutdown hysteresis 20 °C Notes: 3. Exceeding the absolute maximum ratings may damage the device. 4. The device is not guaranteed to function outside its operating ratings. 5. Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5kΩ in series with 100pF. 6. Specification for packaged product only. March 20, 2014 4 Revision 1.1 Micrel, Inc. MIC4930 Typical Characteristics March 20, 2014 5 Revision 1.1 Micrel, Inc. MIC4930 Typical Characteristics (Continued) Switching Frequency vs. Temperature SWITCHING FREQUENCY (MHz) 3.0 2.8 2.6 2.4 VIN = 3.3V VOUT = 1.8V IOUT = 0A 2.2 2.0 -50 -20 10 40 70 100 130 TEMPERATURE (°C) March 20, 2014 6 Revision 1.1 Micrel, Inc. MIC4930 Functional Characteristics March 20, 2014 7 Revision 1.1 Micrel, Inc. MIC4930 Functional Characteristics (Continued) March 20, 2014 8 Revision 1.1 Micrel, Inc. MIC4930 Functional Block Diagram March 20, 2014 9 Revision 1.1 Micrel, Inc. MIC4930 FB To program the output voltage, an external resistive divider network is connected to this pin from the output voltage to AGND, as shown in the Typical Application circuit on page 1, and is compared to the internal 0.625V reference within the regulation loop. The following formula is used to program the output voltage. Functional Description PVIN The power input (PVIN) pin provides power to the internal MOSFETs for the switch mode regulator section of the MIC4930. The input supply operating range is from 2.7V to 5.5V. A low-ESR ceramic capacitor of at least 10µF is required to bypass from PVIN to (power) GND. See the Application Information section for further details. R1 VOUT VREF 1 R2 AVIN The analog power input (AVIN) pin provides power to the internal control and analog supply circuitry. Careful layout should be considered to ensure that high-frequency switching noise caused by PVIN is reduced before reaching AVIN. Always place a 1µF minimum ceramic capacitor very close to the IC between the AVIN and AGND pins. For additional high-frequency switching noise attenuation, RC filtering can be used (R = 10Ω). Eq. 1 Recommended feedback resistor values: EN A logic high signal on the enable (EN) pin activates the output of the switch. A logic low on EN deactivates the output and reduces the supply current to a nominal 0.01µA. Do not leave this pin floating. VOUT R1 R2 1.0V 120k 180k 1.2V 274k 294k 1.5V 316k 226k 1.8V 301k 160k 2.5V 316k 105k 3.3V 309k 71.5k The feed-forward capacitor (CF in the Typical Application diagram) is typically in the range of 22pF to 39pF. The MIC4930 features an internal ripple injection network, whose current is injected into the FB node and integrated by CF. Thus, the waveform at FB is approximately a triangular ripple. The size of CF dictates the amount of ripple amplitude at the FB node. Smaller values of C F yield higher FB ripple amplitudes and better stability, but also somewhat degrade line regulation and transient response. SW The switch (SW) pin connects directly to one side of the inductor and provides the current path during switching cycles. The other end of the inductor is connected to the load and output capacitor. Due to the high speed switching on this pin, the switch node should be routed away from sensitive nodes whenever possible to avoid unwanted injection of noise. PGND The power ground (PGND) pin is the ground return terminal for the high current in the switching node SW. The current loop for the PGND should be as short as possible and kept separate from the AGND net whenever applicable. Hyper Speed Control™ MIC4930 uses an ON- and OFF-time proprietary ripplebased control loop that features three different timers: AGND The analog ground (AGND) pin is the ground return terminal for the biasing and control circuitry. The current loop for the signal ground should be separate from the power ground (PGND) loop. Refer to the Layout Recommendations for further details. Minimum ON Time Maximum ON Time Minimum OFF Time When the required duty cycle is very low, the required OFF time is typically far from the minimum OFF time limit (about 176ns typically). In this case, the MIC4930 operates by delivering a determined ON time at each switching cycle, depending on the input voltage. A new ON time is invoked by the error comparator when the FB voltage falls below the regulation threshold. In this mode, the MIC4930 operates as an adaptive constant-ON-time ripple controller with nearly constant switching frequency. Regulation takes place by controlling the valley of the FB ripple waveform. PG The power-is-good (PG) pin is an open-drain output that indicates logic high when the output voltage is typically above 88% of its steady-state voltage. A pull-up resistor of 10kΩ or greater should be connected from PG to VOUT. When higher duty cycles are required, regulation can no longer be maintained by decreasing the OFF time below March 20, 2014 10 Revision 1.1 Micrel, Inc. MIC4930 the minimum OFF time limit. When this limit is reached, the OFF time is no longer reduced, and the MIC4930 smoothly transitions to an ON-time modulation mode. In the ON-time modulation region, frequency reduces with the increase of the required ON-time / duty cycle, and regulation finally takes place on the peak of the FB ripple waveform. Note that because of the shift of the regulation threshold between different modes, line regulation might suffer when the input voltage and/or duty cycle variations force the MIC4930 to switch form one regulation mode to the other. In applications where wide input voltage variations are expected, ensure that the line regulation is adequate for the intended application. March 20, 2014 11 Revision 1.1 Micrel, Inc. MIC4930 Also pay attention to the inductor saturation characteristic in current limit. The inductor should not heavily saturate even in current limit operation, otherwise the current might instantaneously run away and reach potentially destructive levels. Typically, ferrite-core inductors exhibit an abrupt saturation characteristic, while powedered-iron or composite inductors have a soft-saturation characteristic. Application Information The MIC4930 is a highly efficient, 3A synchronous buck regulator ideally suited for supplying processor core and I/O voltages from a 5V or 3.3V bus. Input Capacitor A 10µF ceramic capacitor or greater should be placed close to the PVIN pin and PGND pin for bypassing. A X5R or X7R temperature rating is recommended for the input capacitor. Take into account C vs. bias effect in order to estimate the effective capacitance and the input ripple at the VIN voltage. Peak current can be calculated by using Equation 2. 1 VOUT /VIN IPEAK IOUT VOUT 2 f L Output Capacitor The MIC4930 is designed for use with a 10µF or greater ceramic output capacitor. Increasing the output capacitance will lower output ripple and improve load transient response. A low equivalent series resistance (ESR) ceramic output capacitor is recommended based upon performance, size, and cost. Ceramic capacitors with X5R or X7R temperature ratings are recommended. Inductance Rated current value Size requirements DC resistance (DCR) Core losses The size of the inductor depends on the requirements of the application. Refer to the typical application circuit and Bill of Materials for details. DC resistance (DCR) is also important. While DCR is inversely proportional to size, DCR can represent a significant efficiency loss. Refer to the Efficiency Considerations subsection. Efficiency Considerations Efficiency is defined as the amount of useful output power, divided by the amount of power supplied (see Typical Characteristics section). The MIC4930 is designed for use with a 1µH to 2.2µH inductor. For faster transient response, a 1µH inductor will yield the best result. For lower output ripple, a 2.2µH inductor is recommended. V I Efficiency % OUT OUT V IN IIN Inductor current ratings are generally given in two methods: permissible DC current, and saturation current. Permissible DC current can be rated for a 20°C to 40°C temperature rise. Saturation current can be rated for a 10% to 30% loss in inductance. Ensure that the nominal current of the application is well within the permissible DC current ratings of the inductor, also depending on the allowed temperature rise. Note that the inductor permissible DC current rating typically does not include inductor core losses. These are a very important contribution to the total inductor core loss and temperature increase in high-frequency DC-to-DC converters, since core losses increase with at least the square of the excitation frequency. For more accurate core loss estimation, it is recommended to refer to manufacturers’ datasheets or websites. 100 Eq. 3 There are two types of losses in switching converters; DC losses and switching losses. DC losses are simply the 2 power dissipation of I R. Power is dissipated in the high side switch during the on cycle. Power loss is equal to the high side MOSFET RDSON multiplied by the switch current squared. During the off cycle, the low side N-channel MOSFET conducts, also dissipating power. The device operating current also reduces efficiency. The product of the quiescent (operating) current and the supply voltage represents another DC loss. The current required driving the gates on and off at high frequency and the switching transitions make up the switching losses. At the higher currents for which the MIC4930 is designed, efficiency loss is dominated by MOSFET RDSON and inductor losses. Higher input supply voltages will increase the gate-to-source threshold on the internal MOSFETs, thereby reducing the internal RDSON. This improves efficiency by reducing DC losses in the device. All but the inductor losses are inherent to the device. In that case, When saturation current is specified, make sure that there is enough design margin, so that the peak current does not cause the inductor to enter saturation. March 20, 2014 Eq. 2 As shown by the calculation above, the peak inductor current is inversely proportional to the switching frequency and the inductance. The lower the switching frequency or inductance, the higher the peak current. As input voltage increases, the peak current also increases. Inductor Selection When selecting an inductor, it is important to consider the following factors: 12 Revision 1.1 Micrel, Inc. MIC4930 inductor selection becomes increasingly critical in efficiency calculations. As the inductors are reduced in size, the DC resistance (DCR) can become quite significant. The DCR losses can be calculated as in: 2 PDCR = IOUT x DCR The injected ripple is ΔVFB(pp) VIN K div D (1 - D) Eq. 4 1 fSW Eq. 6 with Kdiv given by From that, the loss in efficiency due to inductor DCR and core losses (PCORE) can be calculated as in Equation 5. VOUT I OUT 100 Efficiency Loss (%) 1 VOUT I OUT PDCR PCORE K div R1//R2 R inj R1//R2 Eq. 7 Eq. 5 and External Ripple Injection The MIC4930 control loop is ripple-based, and relies on an internal ripple injection network to generate enough ripple amplitude at the FB pin when negligible output voltage ripple is present. The internal ripple injection network is typically sufficient when recommended R1-R2 and CF values are used. The FB ripple amplitude should fall in the 20mV to 100mV range. VIN = Power stage input voltage D = VOUT/VIN = Duty cycle fSW = Switching frequency τ = (R1//R2//Rinj) × CF In Equations 6 and 7, it is assumed that the time constant associated with CF must be greater than the switching period. If significantly lower divider resistors and/or higher C F values are used, the amount of internal ripple injection may not be sufficient for stable operation. In this case, external ripple injection is needed. This is accomplished by connecting a series Rinj-Cinj circuit between the SW and the FB pins, as shown in Figure 1. 1 T 1 fSW Eq. 8 Figure 1. External Ripple Injection March 20, 2014 13 Revision 1.1 Micrel, Inc. MIC4930 Evaluation Board Circuit Bill of Materials Item C1, C2 Part Number C2012X5R1A106M125AB Manufacturer Description Qty. (7) TDK Ceramic capacitor, 10µF, 10V X5R, Size 0805 2 Ceramic capacitor, 22pF, 50V, C0G, Size 0603 1 Ceramic capacitor, 1µF, 10V, X5R, Size 0603 1 C5 DNP, Size 0603 0 C6 DNP, Size 1210 0 C7 DNP, Radial, 8mm diameter polarized capacitor 0 C3 C4 L1 GRM219R61A106ME44 C1608C0G1H220J080AA GRM1885C1H220JA01 C1608X5R1A105M080AC GRM185R61A105ME26 Murata (8) TDK Murata TDK Murata RLF7030T-1R0N6R4 TDK 1µH, 6.4A, 7.3mΩ, L7.3mm × W6.8mm × H3.2mm CLF6045T-1R0N TDK 1µH, 4.5A, 11mΩ, L6.2mm × W5.9mm × H4.5mm VLP6045LT-1R0N TDK 1µH, 6.5A, 13mΩ, L6.8mm × W6.8mm × H4.5mm CDRH5D28RH125NP1R0PC Sumida R1 CRCW06033013FK Vishay R2 CRCW06031603FK (9) (10) Vishay R3 1 1µH, 4.1A, 13.5mΩ, L6.3mm × W6.2mm × H3.0mm Resistor, 301kΩ, Size0603 1 Resistor, 160kΩ, Size 0603 1 DNP, Size 0603 0 R4 CRCW060310R0FK Vishay Resistor, 10Ω, Size 0603 1 R5 CRCW06031002FK Vishay Resistor, 10kΩ, Size 0603 1 R6 CRCW06031003FK Vishay Resistor, 100kΩ, Size 0603 1 R7 CRCW060349R9FK Vishay Resistor, 49.9Ω, Size 0603, for monitoring SW node only 1 Hyper Speed Control™ 3A Buck Regulator 1 U1 MIC4930YFL (11) Micrel, Inc. Notes: 7. TDK: www.tdk.com. 8. Murata: www.murata.com. 9. Sumida: www.sumida.com. 10. Vishay: www.vishay.com. 11. Micrel, Inc.: www.micrel.com. March 20, 2014 14 Revision 1.1 Micrel, Inc. MIC4930 PCB Layout Recommendations Top Layer Bottom Layer March 20, 2014 15 Revision 1.1 Micrel, Inc. MIC4930 Package Information(12) 10-Pin DFN 3mm x 4mm (FL) Note: 12. Package information is correct as of the publication date. For updates and most current information, go to www.micrel.com. March 20, 2014 16 Revision 1.1 Micrel, Inc. MIC4930 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. © 2014 Micrel, Incorporated. March 20, 2014 17 Revision 1.1