MIC23051 4MHz PWM Buck Regulator with HyperLight Load™ and Voltage Scaling General Description Features The Micrel MIC23051 is a high efficiency 600mA PWM HyperLight Load™ • Input voltage: 2.7V to 5.5V synchronous buck (step-down) regulator featuring • 600mA output current HyperLight Load™, a patented switching scheme that • Fixed output voltage from 0.72V to 3.3V offers best in class light load efficiency and transient • Output voltage scaling option performance while providing very small external • Ultra fast transient response components and low output ripple at all loads. • 20µA typical quiescent current The MIC23051 has an output voltage scaling feature that can toggles between two different voltage levels. • 4MHz in CCM PWM operation in normal mode The MIC23051 also has a very low typical quiescent • 0.47µH to 2.2µH inductor current draw of 20µA and can achieve over 85% efficiency • Low voltage output ripple even at 1mA. The device allows operation with a tiny – 25mVpp in HyperLight Load mode inductor ranging from 0.47µH to 2.2µH and uses a small – 3mV output voltage ripple in full PWM mode output capacitor that enables a sub-1mm height solution. • >93% efficiency In contrast to traditional light load schemes HyperLight • ~85% at 1mA Load™ architecture does not need to trade off control speed to obtain low standby currents and in doing so the • Micropower shutdown device only needs a small output capacitor to absorb the • Available in 8-pin 2mm x 2mm MLF® load transient as the powered device goes from light load • –40°C to +125°C junction temperature range to full load. At higher loads the MIC23051 provides a constant Applications switching frequency of greater than 4MHz while providing peak efficiencies greater than 93%. • Cellular phones The MIC23051 is available in fixed output voltage options • Digital cameras from 0.72V to 3.3V eliminating external feedback • Portable media players components. The MIC23051 is available in an 8-pin 2mm x ® • Wireless LAN cards 2mm MLF with a junction operating range from –40°C to • WiFi/WiMax/WiBro modules +125°C. • USB Powered Devices Data sheets and support documentation can be found on Micrel’s web site at: www.micrel.com. ____________________________________________________________________________________________________________ Typical Application Efficiency V OUT = 1.8V 100 90 VIN = 2.7V VIN = 3.6V 80 VIN = 3.3V 70 60 50 1 HyperLight Load is a trademark of Micrel, Inc. MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc. VOUT = 1.8V L = 1µH 10 100 1000 OUTPUT CURRENT (mA) Protected by US Patent No. 7064531 Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com July 2009 M9999-070809-F Micrel, Inc. MIC23051 Ordering Information Part Number Marking Voltage Scaled to with VSC low Nominal Output Voltage Junction Temp. Range Package JCG 1.0V 1.8V –40° to +125°C 8-Pin 2x2 MLF® Pb-Free –40° to +125°C ® Pb-Free ® MIC23051-CGYML MIC23051-C4YML JC4 1.0V 1.2V Lead Finish 8-Pin 2x2 MLF MIC23051-16YML J16 1.15V 1.40V –40° to +125°C 8-Pin 2x2 MLF Pb-Free MIC23051-945YML 945 0.95V 1.25V –40° to +125°C 8-Pin 2x2 MLF® Pb-Free Note 1. Other output voltage combinations (0.72 to 3.3V) available, contact Micrel Marketing for details. 2. MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free. 3. Over bar symbol ( ¯¯ ) may not be to scale. ® Pin Configuration SW 1 8 PGND EN 2 7 VIN VSC 3 6 AGND SNS 4 5 CFF 8-Pin 2mm x 2mm MLF® (Top View) Pin Description Pin Number Pin Name 1 SW Switch (Output): Internal power MOSFET output switches. 2 EN Enable (Input). Logic low will shut down the device, reducing the quiescent current to less than 4µA. Do not leave floating. 3 VSC Voltage scaling pin (input): A low on this pin will scale the output voltage down to specified level. Do not leave floating. 4 SNS Connect to VOUT to sense output voltage. 5 CFF Feed Forward Capacitor. Connect a 560pF capacitor. 6 AGND July 2009 7 VIN 8 PGND Pin Name Analog Ground. Supply Voltage (Input): Requires bypass capacitor to GND. Power Ground. 2 M9999—070809-F Micrel, Inc. MIC23051 Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN) .........................................................6V Output Switch Voltage (VSW) ............................................6V Output Switch Current (ISW)..............................................2A Logic Input Voltage (VEN, VLQ)........................... VIN to –0.3V Storage Temperature Range (Ts)..............–65°C to +150°C ESD Rating(3) .................................................................. 3kV Supply Voltage (VIN)......................................... 2.7V to 5.5V Logic Input Voltage (VEN) ....................................-0.3V to VIN Junction Temperature (TJ) ..................–40°C ≤ TJ ≤ +125°C Thermal Resistance 2x2 MLF-8 (θJA) .................................................90°C/W Electrical Characteristics(4) TA = 25°C with VIN = VEN = VSC = 3.6V; L = 1µH; CFF = 560pF; COUT = 4.7µF; IOUT = 20mA unless otherwise specified. Bold values indicate –40°C< TJ < +125°C. Parameter Supply Voltage Range Under-Voltage Lockout Threshold UVLO Hysteresis Quiescent Current, Hyper LL mode Shutdown Current Condition Min Typ (turn-on) 2.45 IOUT = 0mA , SNS > 1.8V VIN = 5.5V; VEN = 0V; Max Units 5.5 2.55 100 2.65 V V mV 20 35 µA 0.01 4 µA % % % % µA A % % % % 2.7 VSC High, VIN = 3.0V, ILOAD = 20mA -2.5 +2.5 VSC Low, VIN = 3.0V, ILOAD = 20mA -2.5 +2.5 Output Voltage Accuracy SNS pin input current Current Limit in PWM Mode Output Voltage Line Regulation Output Voltage Load Regulation Output Voltage Line Regulation Output Voltage Load Regulation Maximum Duty Cycle PWM Switch ON-Resistance** See Design Note Frequency SoftStart Time VSC threshold voltage VSC hysteresis Output transition time Enable Threshold Enable Hysteresis Enable Input Current Over-temperature Shutdown Over-temperature Shutdown Hysteresis VOUT = 1V SNS = 0.9*VNOM VIN = 3.0V to 5.5V, ILOAD = 20mA, VSC = 3.6V 20mA < ILOAD < 500mA, VSC = 3.6V VIN = 3.0V to 5.5V, ILOAD = 20mA, VSC = 0V 20mA < ILOAD < 500mA, VSC = 0V SNS ≤ VNOM, VOUT = 1.8V ISW = 100mA PMOS ISW = -100mA NMOS VSC = 3.6V, ILOAD = 120mA VSC = 0V, ILOAD = 120mA VOUT = 90% 0.65 80 1 1 0.5 0.3 0.5 0.3 1.7 89 0.45 0.5 4 4 650 0.5 1.2 20 800 VSC from low to high VSC from high to low (turn-on) % Ω Ω MHz MHz µs V mV µs 800 0.5 1.2 35 0.1 165 20 2 V mV µA °C °C Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF. 4. Specification for packaged product only. July 2009 3 M9999—070809-F Micrel, Inc. MIC23051 Typical Characteristics Efficiency V OUT = 1.2V Efficiency VOUT = 1.8V 90 100 90 VIN = 2.7V 90 VIN = 2.7V 80 VIN = 3.6V 80 VIN = 3.3V Efficiency VOUT = 1V 80 VIN = 3.6V VIN = 3.6V VIN = 3.3V 70 70 70 60 50 1 40 60 VOUT = 1.8V L = 1µH 10 100 1000 OUTPUT CURRENT (mA) Quiescent Current vs. Temperature 30 VIN = 3.6V VOUT = 1.8V 20 40 60 80 TEMPERATURE (°C) Switching Frequency vs. Input Voltage 5.0 35 30 4.5 0.80 0.78 4.0 0.70 0.68 1.90 3.2 3.7 4.2 4.7 5.2 INPUT VOLTAGE (V) Output Voltage vs. Input Voltage 0.60 1.90 1.85 1.80 1.8 1.75 1.75 July 2009 Feedback Voltage vs. Temperature Load = 20mA 3.2 3.7 4.2 4.7 5.2 INPUT VOLTAGE (V) 1.70 0 Switching Frequency vs. Temperature 3.0 2.5 1.90 VIN = 3.6V VOUT = 1.8V Load = 150mA 20 40 60 80 TEMPERATURE (°C) Output Voltage vs. Temperature 1.85 1.80 VIN = 3.6V VOUT = 1.8V No Load 0.64 0.62 1.85 1.70 2.7 3.2 3.7 4.2 4.7 5.2 INPUT VOLTAGE (V) 0.66 VIN = 3.6V VOUT = 1.8V Load = 150mA 10 100 1000 OUTPUT CURRENT (mA) 3.5 VIN = 3.6V VOUT = 1.8V No Load 10 5 0 2.7 VOUT = 1V L = 1µH 4.0 0.76 3.5 5.5 5.0 0.74 0.72 2.5 2.7 Quiescent Current vs. Input Voltage 50 1 40 4.5 3.0 10 100 1000 OUTPUT CURRENT (mA) 15 10 5.5 50 45 VIN = 3.3V 60 VOUT = 1.2V L = 1µH 25 20 20 0 50 1 VIN = 2.7V 20 40 60 80 TEMPERATURE (°C) 1.75 1.70 VIN = 3.6V VOUT = 1.8V No Load 20 40 60 80 TEMPERATURE (°C) Output Voltage vs. Load VIN = 3.6V 100 200 300 400 500 600 LOAD (mA) 4 M9999—070809-F Micrel, Inc. MIC23051 Functional Characteristics July 2009 5 M9999—070809-F Micrel, Inc. MIC23051 Functional Characteristics (continued) July 2009 6 M9999—070809-F Micrel, Inc. MIC23051 Functional Diagram VIN VSC EN CONTROL LOGIC TIMER & SOFTSTART UVLO GATE DRIVE SW REFERENCE Current Limit ZERO 1 ISENSE PGND SNS ERROR COMPARATOR R15 CFF R17 AGND MIC23051 Simplified Block Diagram July 2009 7 M9999—070809-F Micrel, Inc. MIC23051 Functional Description VIN VIN provides power to the MOSFETs for the switch mode regulator section and to the analog supply circuitry. Due to the high switching speeds, a 2.2µF or greater capacitor is recommended close to VIN and the power ground (PGND) pin for bypassing. Refer to the layout recommendations for details. EN The enable pin (EN) controls the on and off state of the device. A logic high on the enable pin activates the regulator, while a logic low deactivates it. MIC23051 features built-in soft-start circuitry that reduces in-rush current and prevents the output voltage from overshooting at start up. Do not leave floating. CFF The CFF pin is connected to the SNS pin of MIC23051 with a feed-forward capacitor of 560pF. The CFF pin itself is compared with the internal reference voltage (VREF) of the device and provides the control path to control the output. VREF is equal to 0.72V. The CFF pin is sensitive to noise and should be place away from the SW pin. Refer to the layout recommendations for details. VSC The voltage scaling pin (VSC) is used to switch between two different voltage levels. A logic high on the VSC pin will set the output voltage to the higher voltage. A logic low on the VSC pin will set the output voltage to the lower voltage. Do not leave floating. SW The switch (SW) pin connects directly to the inductor and provides the switching current necessary to operate in PWM mode. Due to the high speed switching on this pin, the switch node should be routed away from sensitive nodes such as the CFF pin. PGND Power ground (PGND) is the ground path for the high current PWM mode. The current loop for the power ground should be as small as possible and separate from the Analog ground (AGND) loop. Refer to the layout recommendations for more details. SNS An inductor is connected from the SW pin to the SNS pin. The SNS pin is the output pin of the device and a minimum of 2.2µF bypass capacitor should be connected in shunt. In order to reduce parasitic inductance it is good practice to place the output bypass capacitor as close to the inductor as possible. AGND Signal ground (AGND) is the ground path 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 more details. July 2009 8 M9999—070809-F Micrel, Inc. Applications Information Input Capacitor A minimum of 2.2µF ceramic capacitor should be placed close to the VIN pin and PGND pin for bypassing. X5R or X7R dielectrics are recommended for the input capacitor. Y5V dielectrics, aside from losing most of their capacitance over temperature, they also become resistive at high frequencies. This reduces their ability to filter out high frequency noise. Output Capacitor The MIC23051 was designed for use with a 2.2µF or greater ceramic output capacitor. A low equivalent series resistance (ESR) ceramic output capacitor either X7R or X5R is recommended. Y5V and Z5U dielectric capacitors, aside from the undesirable effect of their wide variation in capacitance over temperature, become resistive at high frequencies. Inductor Selection Inductor selection will be determined by the following (not necessarily in the order of importance); • Inductance • Rated current value • Size requirements • DC resistance (DCR) The MIC23051 was designed for use with an inductance range from 0.47µH to 2.2µH. Typically, a 1µH inductor is recommended for a balance of transient response, efficiency and output ripple. For faster transient response a 0.47µH inductor may be used. For lower output ripple, a 2.2µH is recommended. Maximum current ratings of the inductor are generally given in two methods; permissible DC current and saturation current. Permissible DC current can be rated either for a 40°C temperature rise or a 10% to 20% loss in inductance. Ensure the inductor selected can handle the maximum operating current. When saturation current is specified, make sure that there is enough margin so that the peak current of the inductor does not cause it to saturate. Peak current can be calculated as follows: MIC23051 significant efficiency Considerations. July 2009 Refer to the Efficiency Compensation The MIC23051 is designed to be stable with a 0.47µH to 2.2µH inductor with a 2.2µF ceramic (X5R) output capacitor. Efficiency Considerations Efficiency is defined as the amount of useful output power, divided by the amount of power supplied. ⎛V ⎞ ×I Efficiency_% = ⎜⎜ OUT OUT ⎟⎟ × 100 ⎝ VIN × IIN ⎠ Maintaining high efficiency serves two purposes. It reduces power dissipation in the power supply, reducing the need for heat sinks and thermal design considerations and it reduces consumption of current for battery powered applications. Reduced current draw from a battery increases the devices operating time and is critical in hand held devices. There are two types of losses in switching converters; DC losses and switching losses. DC losses are simply the power dissipation of I2R. 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 Current2. During the off cycle, the low side N-channel MOSFET conducts, also dissipating power. Device operating current also reduces efficiency. The product of the quiescent (operating) current and the supply voltage is another DC loss. The current required driving the gates on and off at a constant 4MHz frequency and the switching transitions make up the switching losses. Efficiency V OUT = 1.8V 100 90 VIN = 2.7V VIN = 3.6V 80 VIN = 3.3V 70 60 IPK = IOUT + VOUT (1-VOUT/VIN)/2fL As shown by the previous calculation, the peak inductor current is inversely proportional to the switching frequency and the inductance; the lower the switching frequency or the inductance the higher the peak current. As input voltage increases the peak current also increases. The size of the inductor depends on the requirements of the application. Refer to the Application Circuit and Bill of Material for details. DC resistance (DCR) is also important. While DCR is inversely proportional to size, DCR can represent a loss. 50 1 VOUT = 1.8V L = 1µH 10 100 1000 OUTPUT CURRENT (mA) The Figure above shows an efficiency curve. From no load to 100mA, efficiency losses are dominated by quiescent current losses, gate drive and transition losses. By using the HyperLight Load mode the MIC23051 is able to maintain high efficiency at low output currents. Over 100mA, efficiency loss is dominated by MOSFET RDSON and inductor losses. Higher input supply voltages will increase the Gate to Source threshold on the internal 9 M9999—070809-F Micrel, Inc. MOSFETs, 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 which case, 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 follows; L_Pd = IOUT2 × DCR From that, the loss in efficiency due to inductor resistance can be calculated as follows; ⎡ ⎛ ⎞⎤ VOUT × IOUT ⎟⎥ × 100 Efficiency_Loss = ⎢1 − ⎜⎜ ⎟ ⎣⎢ ⎝ VOUT × IOUT + L_Pd ⎠⎦⎥ Efficiency loss due to DCR is minimal at light loads and gains significance as the load is increased. Inductor selection becomes a trade-off between efficiency and size in this case. MIC23051 HyperLight Load Mode™ MIC23051 uses a minimum on and off time proprietary control loop. 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. When the output voltage is over the regulation threshold, the error comparator turns the PMOS off for a minimum-off-time. 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 MIC23051 works in pulse frequency modulation (PFM) to regulate the output. As the output current increases, the switching frequency increases. This improves the efficiency of MIC23051 during light load currents. As the load current increases, the MIC23051 goes into continuous conduction mode (CCM) at a constant frequency of 4MHz. The equation to calculate the load when the MIC23051 goes into continuous conduction mode may be approximated by the following formula: ⎛ (V − VOUT ) × D ⎞ ILOAD = ⎜ IN ⎟ 2L × f ⎝ ⎠ July 2009 10 M9999—070809-F Micrel, Inc. MIC23051 MIC23051 Typical Application Circuit Bill of Materials Item Part Number Manufacturer (1) Description Qty C1, C2 C1608X5R0J476K TDK 4.7µF Ceramic Capacitor, 6.3V, X5R, Size 0603 2 C3 C1608C0G1H561J TDK(1) 560pF Ceramic Capacitor, 50V, NPO, Size 0603 1 LQM21PN1R0MC0D LQH32CN1R0M33 L1 LQM31PN1R0M00 CPL2512T1R0M LQM31PNR47M00 MIPF2520D1R5 U1 MIC23051-xxYML Murata(2) (2) Murata (2) Murata TDK(1) Murata(2) FDK (3) Micrel, Inc. (4) 1µH, 0.8A, 190mΩ, L2mm x W1.25mm x H0.5mm 1µH, 1A, 60mΩ, L3.2mm x W2.5mm x H2.0mm 1µH, 1.2A, 120mΩ, L3.2mm x W1.6mm x H0.95mm 1 1µH, 1.5A, 100mΩ, L2.5mm x W1.5mm x H1.2mm 0.47µH, 1.4A, 80mΩ, L3.2mm x W1.6mm x H0.85mm 1.5µH, 1.5A, 70mΩ, L2.5mm x W2mm x H1.0mm 4MHz PWM Buck Regulator with HyperLight Load Mode 1 Notes: 1. TDK: www.tdk.com 2. Murata: www.murata.com 3. FDK: www.fdk.co.jp 4. Micrel, Inc: www.micrel.com July 2009 11 M9999—070809-F Micrel, Inc. MIC23051 PCB Layout Recommendations Top Layer Bottom Layer July 2009 12 M9999—070809-F Micrel, Inc. MIC23051 Package Information 8-Pin 2mm x 2mm MLF® (ML) 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 The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. 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. © 2007 Micrel, Incorporated. July 2009 13 M9999—070809-F