MIC2253 3.5A 1MHz High Efficiency Boost Regulator with OVP and Softstart General Description Features The MIC2253 is a high power density 1MHz PWM DC/DC boost regulator. The 3.5A minimum switch current limit combined with a 1MHz switching frequency allows the MIC2253 to use smaller inductors and deliver high power in a tiny solution size. The 2.5V to 10V input voltage range of MIC2253 allows direct operation from 1 and 2 cell Li-ion as well as 3 to 4 cell NiCad, NiMH, Alkaline or lithium batteries. Maximum battery life is assured with a low 0.1µA shutdown current. The MIC2253 is available in a low profile 12-pin 3mm x 3mm MLF© package. To prevent a high inrush current, a minimum 1ms soft-start period is set by default and the MIC2253 has the ability to extend the soft-start period with an external capacitor. Datasheet and support documentation can be found on Micrel’s web site at: www.micrel.com. • • • • • • • • • • • • • 3.5A minimum switch current 1.245V ± 3% feedback voltage 2.5V to 10V input voltage Output over-voltage protection (OVP) Externally programmable soft-start Output voltage up to 30V (max) Fixed 1MHz operation <1% line regulation 0.1µA shutdown current Over temperature protection Under-voltage lockout (UVLO) 12-pin 3mm x 3mm leadless MLF® package –40°C to +125°C junction temperature range Applications • Mobile handsets • Portable media/MP3 players • Portable navigation devices (GPS) • WiFi/WiMax/WiBro modules • Digital Cameras • Wireless LAN cards • USB powered devices • Portable applications ___________________________________________________________________________________________________________ Typical Application MLF and MicroLeadFrame are registered 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 April 2011 M9999-042011-C Micrel, Inc. MIC2253 Ordering Information Part Number MIC2253-06YML Marking Code(2) 06 2253 OVP Junction Temp. Range Package Lead Finish 6V –40° to +125°C 12-Pin 3x3 MLF® Pb-Free ® Note: MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free. Pin Configuration ® 12-Pin 3mm x 3mm MLF (ML) (Top View) Pin Description Pin Number Pin Name 1 NC No connect. Not internally connected. 2 SS Soft start (Input). Connect a capacitor to GND to slowly turn on the device. The higher the capacitance, the longer the turn-on time. 3 FB Feedback (Input): Output voltage sense node. Connect external resistors to set the output voltage. Nominal feedback voltage is 1.245V. April 2011 Pin Function 4 AGND Analog Ground 5,6 PGND Power Ground 7,8 SW Switch Node: Internal power BIPOLAR collector. 9 OVP Over-Voltage Protection (OVP): Connect to the output voltage to clamp the maximum output voltage. A resistor divider from this pin to ground could be used to raise the OVP level beyond 6V (max). 10 VIN Supply (Input): 2.5V to 10V for internal circuitry. 11 EN Enable (Input): Applying 1.5V or greater enables the regulator. Applying a voltage of 0.4V or less disables the MIC2253. Do not leave floating. 12 COMP Compensation pin (Input): Add external R and C to GND to stabilize the converter. EP HS Pad Exposed Heat-Sink pad. 2 M9999-042011-C Micrel, Inc. MIC2253 Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN) .......................................................12V Switch Voltage (VSW)....................................... –0.3V to 34V Enable Voltage (VEN)....................................... –0.3V to 12V FB Voltage (VFB)...............................................................6V Switch Current (ISW) ..................................Internally Limited Ambient Storage Temperature (Ts) ...........–65°C to +150°C ESD Rating(3) .................................................................. 2kV Supply Voltage (VIN).......................................... 2.5V to 10V Enable Voltage (VEN).............................................. 0V to VIN Junction Temperature (TJ) ........................ –40°C to +125°C Package Thermal Impedance 3mm x 3mm MLF-12 (θJA) .................................60°C/W Electrical Characteristics(4) TA = 25°C; VIN = VEN = 3.6V; unless otherwise noted. Bold values indicate –40°C≤ TJ ≤ +125°C. Symbol Parameter Condition Min Typ VIN Supply Voltage Range VUVLO Under-Voltage Lockout 1.8 2.1 2.4 V VOVP Over-Voltage Protection 5.25 5.6 6.3 V 2.5 Max Units 10 V IVIN Quiescent Current VFB >1.245V, Not Switching 15 23 mA ISD Shutdown Current VEN = 0V(5) 0.1 1 µA VFB Feedback Voltage 1.245 1.283 V IFB Feedback Input Current VFB = 1.245V Line Regulation 3.0V ≤ VIN ≤ 4.5V 1.208 -450 nA 0.5 % DMIN Minimum Duty Cycle 10 % DMAX Maximum Duty Cycle 90 % ISW Switch Current Limit VIN = 3.6V VSW Switch Saturation Voltage VIN = 3.6V, ISW = 3.5A ISW Switch Leakage Current VEN Enable Threshold IEN Enable Pin Current fSW Oscillator Frequency ISS Soft start TJ Over-Temperature Threshold Shutdown 3.5 VEN = 0V, VSW = 10V TURN ON 4.75 8 A 350 500 mV 0.01 10 µA 1.5 TURN OFF 0.4 VEN = 10V 0.8 VSS = 0V Hysteresis V 20 40 µA 1 1.2 MHz 30 µA 150 °C 10 °C Notes: 1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(Max), the junction-to-ambient thermal resistance, θ JA, and the ambient temperature, TA. The maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. 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. 5. ISD = IVIN April 2011 3 M9999-042011-C Micrel, Inc. MIC2253 Typical Characteristics V IN =3.3V 80 V IN =3V 60 V IN =2.5V 50 40 30 20 80 80 V IN =4.5V V IN =2.5V L = 2.2µH C = 22µF TA = 25°C 30 600 1200 1800 2400 OUTPUT CURR EN T (mA) 0 L = 2.2µH C = 22µF TA = 25°C 40 30 0 600 1200 1800 2400 OUTPU T CU RRENT (mA) 200 400 600 800 1000 1200 OUTPUT C URRENT (mA) Quiescent Current vs. T emperature Efficiency V OUT =15.0V 17.0 90 V IN =3.3V 50 40 20 0 V IN =4.2V 60 50 0 V IN =5V 70 V IN =3.6V 60 L = 2.2µH C = 22µF TA = 25°C 10 90 70 EFFIC IEN CY (%) EFFICIENC Y (%) 70 90 EFFICIENCY (%) 100 90 Efficiency V OUT =12.0V Efficiency V OUT =5.0V Efficiency V OUT = 3.8V Quiescent Current vs. Input Voltage 17.0 70 QUIESCENT CURRENT ( mA) EFFICIENCY (%) 80 V IN =5V 60 V IN =3.3V V IN =4.2V 50 L = 2.2µH C = 22µF TA = 25°C 40 30 0 16.0 15.5 15.0 14.5 14.0 13.5 13.0 V IN = 3.6V 12.5 V F B = 2.5V Not Switching -40 -20 0 20 40 60 13.0 12.0 V F B = 2.5V Not Switching 2.5 TEMPERATURE(°C) 4.0 5.5 7.0 8.5 10.0 IN PUT VOLTAGE (V) Feedback Voltage vs. T emperature 1200 1.30 1.29 1100 1200 1.28 FEEDBAC K VOLTA GE (V) FREQUENCY ( kHz) 1300 1.27 1000 1100 1000 900 800 V OU T = 12V 700 IOU T = 300mA L = 2.2µH C = 22µF 600 4.0 5.5 7.0 8.5 INPUT VOLTAGE (V) 1.25 900 1.24 1.23 V OU T = 5V 800 V IN = 3.6V Load = 200mA 700 500 2.5 1.26 V OU T = 5V 1.21 V IN = 3.6V Load = 200mA 1.20 -40 -20 10.0 1.22 0 20 40 60 80 100 120 -40 -20 TEMPERATURE (°C) Load Regulation 5.0 12.4 4.9 5.06 12.3 4.8 OUTPUT VOLTA GE (V) 12.5 5.08 12.2 12.1 5.02 12.0 5.00 11.9 4.98 4.96 V OU T = 5V L = 2.2µH C = 22µF TA = 25°C 4.94 4.92 4.90 0 April 2011 400 800 1200 1600 OUTPUT CU RRENT (mA) V OU T = 12V L = 2.2µH C = 22µF TA = 25°C Load = 20mA 11.8 11.7 11.6 20 40 60 80 100 120 Current Limit vs. Input Voltage Line Regulation 5.10 5.04 0 TEMPERATUR E (°C) SW CURRENT LIMIT (A) FREQUENCY (kHz) 14.0 80 100 120 1400 OUTPUT VOLTAGE (V) 15.0 Frequency vs. T emperature Frequency vs. Input Voltage 1500 16.0 11.0 12.0 100 200 300 400 500 600 700 OUTPUT CU RRENT (mA) QUIESCENT CURRENT (mA) 16.5 4.7 4.6 4.5 4.4 4.3 V OU T = 12V L = 2.2µH C = 22µF TA = 25°C 4.2 4.1 11.5 4.0 2.5 4.0 5.5 7.0 8.5 INPUT VOLTAGE (V) 4 10.0 2.5 4.0 5.5 7.0 8.5 INPUT VOLTAGE (V) 10.0 M9999-042011-C Micrel, Inc. MIC2253 Typical Characteristics (Continued) Saturation Voltage vs. Switch Current 1.40 400 1.38 350 1.36 ENABLE THRESHOLD (V) SATURATION VOLTAGE (mV) 450 300 250 200 150 100 V IN = 2.5V 50 Enable T hreshold vs. Input Voltage TA = 25°C 0 1.34 1.32 1.30 1.28 1.26 V OU T = 12V 1.24 IOU T = 20mA L = 2.2µH C = 22µF 1.22 1.20 0.0 April 2011 0.5 1.0 1.5 2.0 2.5 3.0 SWITCH CURRENT (A) 3.5 2.5 4.0 5.5 7.0 8.5 10.0 INPUT VOLTAGE (V) 5 M9999-042011-C Micrel, Inc. MIC2253 Functional Characteristics April 2011 6 M9999-042011-C Micrel, Inc. MIC2253 Functional Diagram The gm error amplifier measures the feedback voltage through the external resistor and amplifies the error between the detected voltage signal from the feedback and the internal reference voltage. The output of the gm error amplifier provides the voltage loop signal that is fed to the other input of the PWM comparator. When the current loop signal exceeds the voltage loop signal the PWM comparator turns off the power transistor. The next oscillator/clock period initiates the next switching cycle, maintaining the constant frequency current-mode PWM control. The enable pin shuts down the output switching and disables control circuitry to reduce input current-toleakage levels. Enable pin input current is approximately zero, at zero volts. Functional Description The MIC2253 is a constant frequency, pulse-widthmodulated (PWM) peak current-mode step-up regulator. The device’s simplified control scheme is illustrated in the block diagram above. A reference voltage is fed into the PWM engine where the duty cycle output of the constant frequency PWM engine is computed from the error, or difference, between the REF and FB voltages. The PWM engine encompasses the necessary circuit blocks to implement a current-mode boost switching power supply. The necessary circuit blocks include, but are not limited to, an oscillator/ramp generator, slope compensation ramp generator, gm error amplifier, current amplifier, PWM comparator, and drive logic for the internal 3.5A bipolar power transistor. Inside the PWM engine, the oscillator functions as a trigger for the PWM comparator that turns on the bipolar power transistor and resets the slope compensation ramp generator. The current amplifier is used to measure the power transistor’s current by amplifying the voltage signal from the sense resistor connected to the emitter of the bipolar power transistor. The output of the current amplifier is summed with the output of the slope compensation ramp generator where the result is connected to one of the inputs of the PWM comparator. April 2011 DC-to-DC PWM Boost Conversion The MIC2253 is a constant-frequency boost converter. It can convert a low DC input voltage to a high DC output voltage. Figure 1 shows a typical circuit. Boost regulation is achieved by turning on an internal switch, which draws current through the inductor. When the switch turns off, the inductor’s magnetic field collapses. This causes the current to be discharged into the output capacitor through an external Schottky diode. The Functional Characteristics show Input Voltage ripple, Output Voltage ripple, SW Voltage, and Inductor Current for 300mA load current. Regulation is achieved by modulating the pulse width i.e., pulse-width modulation (PWM). 7 M9999-042011-C Micrel, Inc. MIC2253 Over-Voltage Protection (OVP) The MIC2253 provides a fixed 5.6V overvoltage protection. The overvoltage functionality will clamp the output voltage to a safe level in the event that a fault condition causes the output voltage to increase beyond control. To ensure the highest level of protection, the MIC2253 OVP pin will shut the switch off when an overvoltage condition is detected, saving itself, the output capacitor, and downstream devices from damage. Two external resistors can be used to change the OVP from the range of 6V to 30V. Be careful not to exceed the 30V rating of the switch. The OVP feature may be disabled by grounding the OVP pin. The OVP pin is connected internally to a reference voltage via a voltage divider circuit. For a 5.6V OVP setting, connect the OVP pin directly to the output voltage as shown in Figure 1. To increase the OVP voltage above 5.6V, an external parallel resistor network can be configured, as shown in Figure 2, with the following equation: Figure 1. Typical Application Circuit Duty Cycle Considerations Duty cycle refers to the switch on-to-off time ratio and can be calculated as follows for a boost regulator: D = 1- VIN VOUT VOVP = 1.245 × However at light loads, the inductor will completely discharge before the end of a switching cycle. The current in the inductor reaches zero before the end of the switching cycle. This is known as discontinuous conduction mode (DCM). DCM occurs when: IOUT < 67k × (R1 + R2) 15k × R2 VIN IPEAK × VOUT 2 where IPEAK < (VOUT - VIN ) ⎛ VIN × ⎜⎜ L×f ⎝ VOUT ⎞ ⎟⎟ ⎠ In DCM, the duty cycle is smaller than in continuous conduction mode. In DCM the duty cycle is given by: D= Figure 2. Adjustable OVP Circuit f × 2 × L × IOUT × (VOUT − VIN ) Note: VIN 1. The maximum value of R2 is 30kΩ. The duty cycle required for voltage conversion should be less than the maximum duty cycle of 90%. Also, in light load conditions where the input voltage is close to the output voltage, the minimum duty cycle can cause pulse skipping. This is due to the energy stored in the inductor causing the output to slightly overshoot the regulated output voltage. During the next cycle, the error amplifier detects the output as being high and skips the following pulse. This effect can be reduced by increasing the minimum load or by increasing the inductor value. Increasing the inductor value also reduces the peak current. Minimum duty cycle is typically 10%. April 2011 Soft Start Functionality The soft start time is dependant up on both CSS and the comp capacitor values. CCOMP is fixed for stable operation (typically 10nF); therefore, if any increases in soft start are desired, this should be done using the CSS capacitor. The approximate total startup time is given by: TSS = 1ms + 85k × CSS 8 M9999-042011-C Micrel, Inc. MIC2253 inductor current and the maximum reverse voltage is rated greater than the output voltage. Component Selection Inductor The MIC2253 is designed to work with a 2.2µH inductor. This is due to the unavoidable “right half plane zero” effect for the continuous current boost converter topology. The frequency at which the right half plane zero occurs can be calculated as follows: Input Capacitor A minimum 2.2µF ceramic capacitor with an X5R or X7R dielectric is recommended for designing with the MIC2253. Increasing input capacitance will improve performance and greater noise immunity on the source. The input capacitor should be as close as possible to the inductor and the MIC2253, with short traces for good noise performance. 2 frhpz = VOUT VIN × L × IOUT × 2π The right half plane zero has the undesirable effect of increasing gain, while decreasing phase. This requires that the loop gain is rolled off before this has significant effect on the total loop response. This can be accomplished by either reducing inductance (increasing RHPZ frequency) or increasing the output capacitor value (decreasing loop gain). Compensation The comp pin is connected to the output of the voltage error amplifier. The voltage error amplifier is a transconductance amplifier. Adding a series RC-toground adds a zero at: fzero = Output Capacitor Output capacitor selection is a trade-off between performance, size, and cost. Increasing output capacitance will lead to an improved transient response, but also an increase in size and cost. X5R or X7R dielectric ceramic capacitors are recommended for designs with the MIC2253. The output capacitor sets the frequency of the dominant pole and zero in the power stage. The zero is given by: fz = The resistor should be set to approximately 600Ω. The capacitor typically ranges from 10nF to 100nF. Adding an optional capacitor from comp pin-to-ground adds a pole at approximately: fpole = C × R esr × 2π Feedback Resistors The feedback pin (FB) provides the control path to the control the output. The FB pin is used to compare the output to an internal reference. Output voltages are adjusted by selecting the appropriate feedback network values. The desired output voltage can be calculated as follows: IOUT C × VOUT × 2 × π ⎛R ⎞ VOUT = VREF ⋅ ⎜⎜ 1 + 1⎟⎟ R ⎝ 2 ⎠ Diode Selection The MIC2253 requires an external diode for operation. A Schottky diode is recommended for most applications due to their lower forward voltage drop and reverse recovery time. Ensure the diode selected can deliver the peak April 2011 1 2πR 2 C 3 This capacitor typically is 100pF. Generally, an RC to ground is all that is needed. The RC should be placed as close as possible to the compensation pin. The capacitor should be a ceramic with a X5R, X7R, or COG dielectric. Refer to the MIC2253 evaluation board document for component location. 1 For ceramic capacitors, the ESR is very small. This puts the zero at a very high frequency where it can be ignored. Fortunately, the MIC2253 is current mode in operation which reduces the need for this output capacitor zero when compensating the feedback loop. The frequency of the pole caused by the output capacitor is given by: fp = 1 2πR 2 C 4 where VREF is equal to 1.245V. 9 M9999-042011-C Micrel, Inc. MIC2253 MIC2253 Sample Schematic April 2011 10 M9999-042011-C Micrel, Inc. MIC2253 Bill of Materials Item C1 Part Number C1608X5R1C225K GRM188R61C225KE15 CL10A225K08NNN C2 C1608X7R1H104K/10 L1 Samsung Capacitor, 0.1µF, 16V, X7R, 0603 size C1608C0G1H101J TDK Capacitor, 100pF, 50V, C0G, 0603 size Murata Capacitor, 100pF, 50V, C0G, 0603 size Samsung Capacitor, 100pF, 50V, C0G, 0603 size AVX(4) Capacitor, 100pF, 50V, C0G, 0603 size C1608X5R1H103K TDK Capacitor, 10nF, 50V, X5R, 0603 size CL10B103KB8NNN Samsung Capacitor, 10nF, 50V, X5R, 0603 size 06035C103KA12A AVX Capacitor, 10nF, 50V, X5R, 0603 size CL21A226MPCLRNC Samsung Taiyo Yuden Schottky Diode, 3A, 20V SK34 MCC Schottky Diode, 3A, 40V LTF5022T-2R2N3R2 TDK Inductor, 2.2µH, 3.4A, 5.2 x 5.0 x 2.2mm RLF7030T-2R2M TDK Inductor, 2,2µH, 5.4A, 6.8 x 7.3 x 3.2mm CRCW06031002FRTI 1 1 (7) (8) Vishay 1 Capacitor, 22µF, 10V, X5R, 0805 size MCC(6) Coilcraft 1 Capacitor, 22µF, 10V, X5R, 0805 size (5) SK32 MOS6020-222ML R1 Capacitor, 2.2µF, 16V, X5R, 0603 size CL10B104KB8NNN LMK212BJ226MG-T D1 Samsung 1 Capacitor, 2.2µF, 16V, X5R, 0603 size (3) Capacitor, 0.1µF, 16V, X7R, 0603 size 06035A101AT2A Qty. Capacitor, 2.2µF, 16V, X5R, 0603 size Murata(2) Murata CL10C101JB8NNN C5 Description Capacitor, 0.1µF, 16V, X7R, 0603 size GRM1885C1H101JA01 C4 TDK (1) TDK GRM188R71H104KA93 C3 Manufacturer 1 1 Inductor, 2.2µH, 3.56A, 6.0 x 7.1 x 2.4mm Resistor, 10kΩ, 1%, 1/16W, 0603 size 1 R2 CRCW06036200FRTI Vishay Resistor, 620Ω, 1%, 1/16W, 0603 size 1 R4 CRCW06031003FRTI Vishay Resistor, 100kΩ, 1%, 1/16W, 0603 size 1 R5 CRCW06033092FRTI Vishay Resistor, 30.9kΩ, 1%, 1/16W, 0603 size 1 1MHz High Efficiency Boost Regulator with OVP and Softstart 1 U1 MIC2253-06YML Micrel, Inc. (9) Notes: 1. TDK: www.tdk.com 2. Murata: www.murata.com 3. Samsung: www.sem.samsung.com 4. AVX: www.avx.com 5. Taiyo Yuden: www.t-yuden.com 6. MCC: www.mccsemi.com 7. Coilcraft: www.coilcraft.com 8. Vishay: www.vishay.com 9. Micrel, Inc.: www.micrel.com April 2011 11 M9999-042011-C Micrel, Inc. MIC2253 Recommended Layout Top Layout Bottom Layout April 2011 12 M9999-042011-C Micrel, Inc. MIC2253 Package Information 12-Pin 3mm x 3mm 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 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. © 2009 Micrel, Incorporated. April 2011 13 M9999-042011-C