MP2249 1MHz, 6V, 3A, Low-Voltage Synchronous Step-Down Converter The Future of Analog IC Technology DESCRIPTION FEATURES • • • • • • • • • • The MP2249 is a 1MHz constant frequency, current mode, PWM step-down converter. The device integrates a main switch and a synchronous rectifier for high efficiency and eliminates the need for an external Schottky diode. It is ideal for powering portable equipment that runs from a single cell LithiumIon (Li+) battery. The MP2249 can supply 3A of load current from a 2.5V to 6V input voltage. It can run at 100% duty cycle for low dropout applications. The MP2249 provides internal soft-start control to reduce rush current and output discharge function to control discharging of the output capacitor. • • • High Efficiency: Up to 90% Power Save Mode at Light Load 1MHz Constant Switching Frequency Up to 4.5A Peak Current 2.5V to 6V Input Voltage Range Output Adjustable from 0.6V to VIN 100% Duty Cycle in Dropout Output Discharge Function Internal Soft-Start Control Power Good Indicator Short Circuit Protection Thermal Fault Protection Available in 3mmx3mm TQFN10 or SOIC8E Package APPLICATIONS The MP2249 is available in small 3mmx3mm TQFN10 or SOIC8E package. • • • • • • Cellular and Smart Phones Microprocessors and DSP Core Supplies PDAs MP3 Players Digital Still and Video Cameras Portable Instruments “MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION R3 VIN / 5V PVIN L1 2.2 H MP2249 PVIN C1 10 VOUT /1.8V SW R1 C2 10 C3 22 FB EN ON OFF MP2249 Rev.1.0 11/2/2010 PG PG GND C4 R2 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 1 MP2249 – 6V, 3A, 1MHZ, SYNCHRONOUS STEP-DOWN CONVERTER RDERING INFORMATION Part Number Package Top Marking MP2249DN SOIC8E MP2249 MP2249DQT * TQFN10 (3mm x 3mm) AAVY Free Air Temperature (TA) -40°C to +85°C * For Tape and Reel, add suffix -Z (e.g. MP2249DQT–Z). For RoHS Compliant Packaging, add suffix - LF (e.g. MP2249DQT–LF–Z); PACKAGE REFERENCE TQFN10 (3mm x 3mm) SOIC8E ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance PVIN to GND ...............................-0.3V to +6.5V SW to GND ............................-0.3V to VIN +0.3V FB, EN & PG to GND...................-0.3V to +6.5V Junction Temperature .............................+150°C Continuous Power Dissipation (TA = +25°C) (2) SOIC8E...................................................... 2.5W TQFN10 (3mmx3mm) ................................ 2.5W Lead Temperature ..................................+260°C Storage Temperature .............. -65°C to +150°C SOIC8E .................................. 50 ...... 10... °C/W TQFN10 (3mmx3mm)............. 50 ...... 12... °C/W Recommended Operating Conditions (3) Supply Voltage VIN .............................2.5V to 6V Output Voltage VOUT ...........................0.6V to 6V Operating Junct. Temp. ........... -40°C to +125°C MP2249 Rev.1.0 11/2/2010 (4) θJA θJC Notes: 1) Exceeding these ratings may damage the device. 2) The maximum allowable power dissipation is a function of the maximum junction temperature. TJ(MAX) the junction-toambient thermal resistance θJA and the ambient temperature TA. The maximum allowable power dissipation at any ambient temperature is calculated using: PD(MAX)=(TJ(MAX)-TA)/ θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 3) The device is not guaranteed to function outside of its operating conditions. 4) Measured on JESD51-7, 4-layer PCB. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 2 MP2249 – 6V, 3A, 1MHZ, SYNCHRONOUS STEP-DOWN CONVERTER ELECTRICAL CHARACTERISTICS VIN = VEN = 3.6V, TA = +25°C, unless otherwise noted. Parameter Symbol Condition Supply Current IQ VEN = VIN, VFB = 0.51V Shutdown Current VEN = 0V, VIN = 6V IN Under Voltage Lockout Rising Edge (UVLO) Threshold IN Under Voltage Lockout Hysteresis Soft-Start Time Discharge MOSFET On Resistance Regulated FB Voltage VFB FB Input Bias Current PFET On Resistance (5) NFET On Resistance (5) SW Leakage Current PFET Current Limit (5) ILIMIT Oscillator Frequency (5) Minimum On Time Thermal Shutdown Threshold (5) Min Typ 480 0.01 Max 600 1 Units µA µA 2.15 2.3 2.45 V 210 mV 1 ms 100 Ω TA = +25°C 0.594 0.600 0.606 -40°C ≤ TA ≤ +85°C VFB = 0.65V ISW = 100mA ISW = -100mA VEN = 0V,VIN = 6V, VSW = 0V or 6V Duty Cycle = 100%, Current Pulse Width < 1ms 0.588 -50 0.600 0.5 92 72 0.612 +50 -1 +1 V nA mΩ mΩ µA 4.5 A fSW 1 MHz tON 100 ns 145 °C Trip EN Turn-on Trip Threshold -40°C ≤ TA ≤ +85°C EN Turn-off Trip Threshold EN-pull down resistor Latch Off Under Voltage (UV) Threshold PG Upper Trip Threshold PG Lower Trip Threshold PG Output Low Voltage -40°C ≤ TA ≤ +85°C 0.4 360 450 1.8 V 540 V kΩ 67% VFB 90% 85% VFB VFB V ISINK=1mA 0.3 Notes: 5) 100% production test at +25°C. Typical and temperature specifications are guaranteed by design and characterization. MP2249 Rev.1.0 11/2/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 3 MP2249 – 6V, 3A, 1MHZ, SYNCHRONOUS STEP-DOWN CONVERTER PIN FUNCTIONS Pin # TQFN10 SOIC8E Name Description Power Switch Output. Inductor connection to drains of the internal PFET and NFET switches. Power-good indicator. PG is pulled low when output is outside the window of regulation or the device enters shutdown. Regulator Enable Control Input. Drive EN above 1.8V to turn on the MP2249. Drive EN below 0.4V to turn it off. EN is pulled to GND with a 450kΩ internal resistor. Feedback Input. Connect FB to the center point of the external resistor divider. The feedback threshold voltage is 0.6V. 6, 7, 8 5, 6 SW 9 7 PG 10 8 EN 1 1 FB 2, 3 Exposed Pad 2, 3 Exposed Pad GND Ground. Connect Exposed Pad to ground plane for optimal thermal performance. 4, 5 4 PVIN Power Stage Supply Input. Bypass to GND with a 2.2µF or bigger ceramic capacitor. MP2249 Rev.1.0 11/2/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 4 MP2249 – 6V, 3A, 1MHZ, SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS VIN = 5V, EN = 5V, VO = 1.8V, L1 = 2.2µH, and TA = +25°C, unless otherwise noted. Efficiency vs. Output Current Steady State Operation IO=0A 100 80 VO/AC 50mV/div VIN=3.3V VIN=2.5V 60 40 SW 2V/div 20 0 0 0.5 1 1.5 2 2.5 3 IL 500mA/div OUTPUT CURRENT (A) Start-up through EN Steady State Operation IO=0A IO=3A VO/AC 50mV/div VO 1V/div PG 5V/div SW 2V/div EN 5V/div IL 5A/div Shut-down through EN Start-up through EN IO=3A IO=0A MP2249 Rev.1.0 11/2/2010 VO 1V/div VO 1V/div PG 5V/div PG 5V/div EN 5V/div EN 5V/div www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 5 MP2249 – 6V, 3A, 1MHZ, SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V, EN = 5V, VO = 1.8V, L1 = 2.2µH, and TA = +25°C, unless otherwise noted. Short Cuit Protection Shut-down through EN IO=0A to short IO=3A VO 1V/div VO 1V/div PG 5V/div SW 2V/div EN 5V/div IL 5A/div 20ms/div Load Transient Short Cuit Protection IO=1.5A to 3A IO=3A to short VO 1V/div SW 2V/div IL 5A/div MP2249 Rev.1.0 11/2/2010 VO/AC 50mV/div SW 5V/div IL 2A/div www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 6 MP2249 – 6V, 3A, 1MHZ, SYNCHRONOUS STEP-DOWN CONVERTER FUNCTION BLOCK DIAGRAM PVIN EN PVIN BIAS & VOLTAGE REFERENCE 0.6V 0.4V 1MHz OSCILLATOR MAIN SWITCH PCH ISLOPE OSC Internal SS FB CONTROL LOGIC COMP 0.6V PWM 600k SW 34pF 1pF 0.4V PG SYNCHRONOUS RECTIFIER NCH OUTPUT DISCHARGE R 0.54V LOW SIDE GATE DRIVE GND Figure 1—Function Block Diagram OPERATION The MP2249 is a constant frequency current mode PWM step-down converter. The MP2249 is optimized for low voltage, Li-Ion battery powered applications where high efficiency and small size are critical. The MP2249 uses an external resistor divider to set the output voltage from 0.6V to 6V. The device integrates both a main switch and synchronous rectifier, which provides high efficiency and eliminates an external Schottky diode. The MP2249 can achieve 100% duty cycle. The duty cycle D of a step-down converter is defined as: D = TON × fOSC × 100% ≈ VOUT × 100% VIN Where TON is the main switch on time, fOSC is the oscillator frequency (1MHz), VOUT is the output voltage and VIN is the input voltage MP2249 Rev.1.0 11/2/2010 Current Mode PWM Control Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for superior load and line response and protection of the internal main switch and synchronous rectifier. The MP2249 switches at a constant frequency (1MHz) and regulates the output voltage. During each cycle the PWM comparator modulates the power transferred to the load by changing the inductor peak current based on the feedback error voltage. During normal operation, the main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. When the main switch is off, the synchronous rectifier will be turned on immediately. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 7 MP2249 – 6V, 3A, 1MHZ, SYNCHRONOUS STEP-DOWN CONVERTER Power Save Mode Operation The MP2249 enters asynchronous mode as soon as current of LS MOS goes below zero. When the load is light enough and comp voltage is lower than the set value, the part goes into power skipping mode. This mode improves efficiency at light load condition. Dropout Operation The MP2249 allows the main switch to remain on for more than one switching cycle and increases the duty cycle while the input voltage is dropping close to the output voltage. When the duty cycle reaches 100%, the main switch is held on continuously to deliver current to the output up to the switch’s current limit. The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. Over-Current-Protection and Latchoff The MP2249 provides cycle-by-cycle over current limit when inductor current peak value exceeds the current limit threshold. Meanwhile, output voltage starts to drop until FB is below the Under-Voltage (UV) threshold, typically 33% below the reference. Once the UV is triggered, the MP2249 enters latched off mode. Internal Soft-Start The soft-start is implemented to prevent the converter output voltage from overshooting during startup. When the chip starts, the internal circuitry generates a soft-start voltage (SS) ramping up from 0V to 1.2V. When it is lower than the internal reference (REF), SS overrides REF so the error amplifier uses SS as the reference. When SS is higher than REF, REF regains control. Output Discharge Function When the device is disabled, the part goes into output discharge mode automatically and its internal discharge MOSFET provides a resistive discharge path for the output capacitor. This function is only suitable for discharge output capacitor for the limited time. If the part is used in a pre-bias application, the external power supply providing the pre-bias should supply larger current than the discharge MOSFET sinks. PG Indicator MP2249 provides an open-drain PG output that goes high after output level reaches regulation after startup. PG is pulled low immediately if the output goes out of regulation level or when device enters shutdown. This protection mode is especially useful when the output is dead-short to ground. The MP2249 exits the latch off mode once the EN or input power is recycled. This operation mode will be masked off for the soft start stage. Maximum Load current The MP2249 can operate down to 2.5V input voltage. However, the maximum load current decreases at lower input due to large IR drop across the main switch and synchronous rectifier. The slope compensation signal reduces the peak inductor current as a function of the duty cycle to prevent sub-harmonic oscillations at duty cycles greater than 50%. Conversely the current limit increases as the duty cycle decreases. MP2249 Rev.1.0 11/2/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 8 MP2249 – 6V, 3A, 1MHZ, SYNCHRONOUS STEP-DOWN CONVERTER APPLICATION INFORMATION Output Voltage Setting The external resistor divider sets the output voltage (see Page 1, Schematic Diagram). The feedback resistor R1 also set the feedback loop bandwidth with the internal compensation. The feedback loop bandwidth (fC) is no higher than 1/10th of switching frequency of MP2249. In the case of output ceramic capacitor as CO, it is usually set in the range of 50kHz and 100kHz for optimal transient performance and good phase margin. If an electrolytic capacitor is used, the loop bandwidth is no higher than 1/4 of the ESR zero frequency (fESR). fESR is given by: fESR = 2π × RESR × CO For example, choose fC=80kHz with a ceramic capacitor, CO=47µF, R1 is estimated to be 150kΩ. R2 is then given by: R1 VOUT −1 0.6V Table 1—Resistor Selection vs. Output Voltage Setting VOUT R1 R2 L COUT (Ceramic) 1.2V 150kΩ 150kΩ 1.5µH-2.2µH 22µF x 2 1.5V 150kΩ 100kΩ 1.5µH-2.2µH 22µF x 2 1.8V 150kΩ 75kΩ 1.5µH-2.2µH 22µF x 2 2.5V 150kΩ 47.5kΩ 1.5µH-2.2µH 22µF x 2 3.3V 150kΩ 33.2kΩ 1.5µH-2.2µH 22µF x 2 Inductor Selection A 1.5µH to 2.2µH inductor with DC current rating at least 25% higher than the maximum load current is recommended for most applications. For best efficiency, the inductor DC resistance shall be <20mΩ. See Table 2 for recommended inductors and Vendors. For most designs, the inductance value can be derived from the following equation: L= MP2249 Rev.1.0 11/2/2010 The maximum inductor peak current is: IL(MAX) = ILOAD + ∆IL 2 Table 2—Suggested Surface Mount Inductors Part Number L (µH) 744777002 2.2 744310200 2 RLF7030T1R5N6R1-T 1.5 8 Vendor DCR (mΩ) SC (A) LxWxH 3 (mm ) 13 6 7.3×7.3×4.5 14.2 6.5 7×6.9×3 6.5 7.8×6.8×3.2 WURTH TDK 1 R2 = where ∆IL is Inductor Ripple Current. Choose inductor ripple current approximately 30% of the maximum load current 3A. VOUTx(VIN - VOUT) VINx∆ILxfOSC Input Capacitor Selection The input capacitor reduces the surge current drawn from the input and the switching noise from the device. The input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current passing to the input source. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most applications, a 47µF capacitor is sufficient. Output Capacitor Selection The output capacitor keeps output voltage ripple small and ensures a stable regulation loop. The output capacitor impedance shall be low at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended. If an electrolytic capacitor is used, pay attention to output ripple voltage, extra heating, and the selection of feedback resistor R1 (refer to “Output Voltage Setting” section) due to the large ESR of electrolytic capacitor. The output ripple ∆VOUT is approximately: ∆VOUT ≤ VOUTx(VIN - VOUT) 1 x(ESR + ) VINxfOSCxL 8xfOSCxCO www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 9 MP2249 – 6V, 3A, 1MHZ, SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL APPLICATION CIRCUIT PG R2 100k VIN C1 10uF 4,5 C2 10uF C3 0.1uF PVIN PG VIN SW 9 L1 6,7,8 R1 100k GND 10 EN FB C6 22uF C7 22uF C8 0.1uF R3 150k 1 GND C5 0.1uF VOUT 2.2uH MP2249DQT C4 1uF GND 2,3 R4 75k Figure 2—Typical application circuit of MP2249DQT PG R2 100k VIN C1 10uF GND 4 C2 10uF PVIN PG C3 0.1uF SW R1 100k L1 5,6 EN FB VOUT 2.2uH MP2249DN 8 C5 0.1uF 7 C6 22uF C7 22uF C8 0.1uF R3 150k 1 GND GND 2,3 R4 75k Figure 3—Typical application circuit of MP2249DN MP2249 Rev.1.0 11/2/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 10 MP2249 – 6V, 3A, 1MHZ, SYNCHRONOUS STEP-DOWN CONVERTER PACKAGE INFORMATION TQFN10 (3mm x 3mm) 2.90 3.10 0.30 0.50 PIN 1 ID MARKING 0.18 0.30 2.90 3.10 PIN 1 ID INDEX AREA 1.45 1.75 PIN 1 ID SEE DETAIL A 10 1 2.25 2.55 0.50 BSC 5 6 TOP VIEW BOTTOM VIEW PIN 1 ID OPTION A R0.20 TYP. PIN 1 ID OPTION B R0.20 TYP. 0.70 0.80 0.20 REF 0.00 0.05 SIDE VIEW DETAIL A NOTE: 2.90 0.70 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH. 3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETER MAX. 4) DRAWING CONFORMS TO JEDEC MO-229, VARIATION VEED-5. 5) DRAWING IS NOT TO SCALE. 1.70 0.25 2.50 0.50 RECOMMENDED LAND PATTERN MP2249 Rev.1.0 11/2/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 11 MP2249 – 6V, 3A, 1MHZ, SYNCHRONOUS STEP-DOWN CONVERTER SOIC8E (exposed pad) 0.189(4.80) 0.197(5.00) 8 0.124(3.15) 0.136(3.45) 5 0.150(3.80) 0.157(4.00) PIN 1 ID 1 0.228(5.80) 0.244(6.20) 0.089(2.26) 0.101(2.56) 4 TOP VIEW BOTTOM VIEW SEE DETAIL"A" 0.013(0.33) 0.020(0.51) 0.051(1.30) 0.067(1.70) SEATING PLANE 0.000(0.00) 0.005(0.125) 0. 0075(0.19) 0. 0098(0.25) SIDE VIEW 0.050(1.27) BSC FRONT VIEW 0.010(0.25) x 45o 0.020(0.50) GAUGE PLANE 0.010(0.25) BSC 0.024(0.61) 0.050(1.27) 0o-8o 0.016(0.41) 0.050(1.27) 0.063(1.60) DETAIL"A" 0.103(2.62) 0.213(5.40) NOTE: 1) 2) 3) 0.138(3.51) RECOMMENDED LAND PATTERN 4) 5) 6) CONTROL DIMENSION IS IN INCHES . DIMENSION IN BRACKET IS IN MILLIMETERS . PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH , PROTRUSIONS OR GATE BURRS . PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS . LEAD COPLANARITY ( BOTTOM OF LEADS AFTER FORMING ) SHALL BE 0.004" INCHES MAX . DRAWING CONFORMS TO JEDEC -MS 012, VARIATION BA . DRAWING IS NOT TO SCALE . NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MP2249 Rev.1.0 11/2/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 12