MP28114 Ultra-small 1.7MHz, 600mA, Low-Voltage Synchronous Step-Down Converter The Future of Analog IC Technology DESCRIPTION FEATURES The MP28114 is a 1.7MHz constant frequency, current mode, ultra-small PWM step-down converter. The device integrates a main switch and a synchronous rectifier for high efficiency and eliminates the needs for an external schottky diode. It is ideal for powering portable equipment that runs from a single cell LithiumIon (Li+) battery. The MP28114 can supply 600mA of load current from a 2.5V to 6V input voltage. The output voltage for the MP28114DG can be regulated as low as 0.6V, while the output voltages of the MP28114DG-1.5, MP28114G-1.8, and MP28114DG-3.3 are fixed at 1.5V, 1.8V, and 3.3V, respectively. The MP28114 can also run at 100% duty cycle for low dropout applications. The MP28114 is available in an ultra-small 2x2mm QFN package. • • • • • • • • • • • • APPLICATIONS • • • • • • ORDERING INFORMATION Part Number MP28114DG - 1.5 MP28114DG - 1.8 MP28114DG - 3.3 MP28114DG High Efficiency: Up to 95% 1.7MHz Constant Switching Frequency 600mA Available Load Current 2.5V to 6V Input Voltage Range Output Voltage as Low as 0.6V 100% Duty Cycle in Dropout Current Mode Control Short Circuit Protection Thermal Fault Protection <0.1µA Shutdown Current 1.5V,1.8V, and 3.3V Fixed Out-put Versions Ultra-Small 2x2mm QFN Package Output Voltage VOUT = 1.5V VOUT = 1.8V VOUT = 3.3V VOUT =0.6 to 6V 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 Efficiency vs Load Current 7 C1 IN SW 1 EN GND 6,8 FB 90 80 MP28114 4 100 OUTPUT L1 5 R1 C2 R2 EFFICIENCY (%) INPUT 2.5V - 6V 70 60 50 40 30 20 10 0 MP28114 Rev.0.92 8/5/2010 10 100 LOAD CURRENT (mA) www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 1000 1 MP28114 – ULTRA-SMALL 1.7mHz, 600mA LOW-VOLTAGE SYNCHRONOUS STEP-DOWN CONVERTER ORDERING INFORMATION Part Number MP28114DG - 1.5 MP28114DG - 1.8 MP28114DG - 3.3 MP28114DG* Package Top Marking Free Air Temperature (TA) 2 X 2mm QFN8 3D 2D AL 4D –40°C to +85°C * For Tape & Reel, add suffix –Z (e.g. MP28114DG–Z). For RoHS Compliant Packaging, add suffix –LF (e.g. MP28114DG–LF–Z) PACKAGE REFERENCE TOP VIEW TOP VIEW SW 1 8 GND SW 1 8 GND NC 2 7 IN NC 2 7 IN NC 3 6 GND NC 3 6 GND EN 4 5 FB EN 4 5 OUT EXPOSED PAD ON BACKSIDE CONNECT TO GND EXPOSED PAD ON BACKSIDE CONNECT TO GND External FB QFN8 (2mm x 2mm) Fixed Output QFN8 (2mm x 2mm) ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance VIN to GND ..................................–0.3V to +6.5V VSW to GND........................... –0.3V to VIN +0.3V VFB, VEN to GND ..........................–0.3V to +6.5V SW Peak Current ........................................ 1.4A (2) Continuous Power Dissipation (TA = +25°C) ........................................................... 1.56W Junction Temperature .............................+150°C (3) Lead Temperature ..............................+260°C Storage Temperature ............. –65°C to +150°C 2x2mm QFN8..........................80 ...... 16 ... °C/W Recommended Operating Conditions (4) Supply Voltage VIN .............................2.5V to 6V Output Voltage VOUT ...........................0.6V to 6V Operating Temperature............. –40°C to +85°C MP28114 Rev.0.92 8/5/2010 (5) 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 continuous power dissipation at any ambient temperature is calculated by 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) For recommended IR reflow temperature information, refer to MPS document MP28114_IRRTP. 4) The device is not guaranteed to function outside of its operating conditions. 5) Measured on JESD51-7 4-layer board. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 2 MP28114 – ULTRA-SMALL 1.7mHz, 600mA LOW-VOLTAGE SYNCHRONOUS STEP-DOWN CONVERTER ELECTRICAL CHARACTERISTICS (6) (continued) VIN = VEN = 3.6V, TA = +25°C, unless otherwise noted. Parameter Supply Current Shutdown Current IN Under Voltage Lockout Threshold IN Under Voltage Lockout Hysteresis Regulated FB Voltage FB Input Bias Current Regulated Output Voltage PFET On Resistance NFET On Resistance SW Leakage Current PFET Current Limit Oscillator Frequency Thermal Shutdown Trip Threshold EN Trip Threshold EN Input Current Symbol Condition VEN = VIN, VFB = 0.65V VEN = 0V, VIN = 6V Min Typ 400 0.01 Max 600 1 Units µA µA Rising Edge 2.10 2.27 2.45 V 55 TA = +25°C, MP28114DG –40°C ≤ TA ≤ +85°C VFB = 0.65V, MP28114DG MP28114DG-1.5 IOUT = 50mA –40°C ≤ TA ≤ +85°C MP28114DG-1.8 IOUT = 50mA –40°C ≤ TA ≤ +85°C MP28114DG-3.3 IOUT = 50mA –40°C ≤ TA ≤ +85°C ISW = 100mA ISW = –100mA VEN = 0V, VIN = 6V VSW = 0V or 6V Duty Cycle = 100%, Current Pulse Width < 1ms mV 0.588 0.582 –50 0.600 0.600 0.5 0.612 0.618 +50 1.455 1.500 1.545 1.746 1.800 1.854 3.201 3.300 3.399 0.44 0.29 –1 nA V Ω Ω +1 µA 0.7 1.0 1.35 A 1.26 1.70 2.08 MHz °C 145 –40°C ≤ TA ≤ +85°C VEN = 0V to 6V V 0.3 –1 0.96 1.5 +1 V µA Notes: 6) 100% production test at +25°C. Typical and temperature specifications are guaranteed by design and characterization. MP28114 Rev.0.92 8/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 3 MP28114 – ULTRA-SMALL 1.7mHz, 600mA LOW-VOLTAGE SYNCHRONOUS STEP-DOWN CONVERTER PIN FUNCTIONS Pin # Name 1 SW 2, 3 NC 4 EN 5 FB 5 OUT 6, 8 7 GND, Exposed Pad IN MP28114 Rev.0.92 8/5/2010 Description Power Switch Output. Inductor connection to drains of the internal PFET and NFET switches. No Connect Regulator Enable Control Input. Drive EN above 1.5V to turn on the MP28114. Drive EN below 0.3V to turn it off (shutdown current < 0.1µA). Feedback Input. Connect FB to the center point of the external resistor divider. The feedback threshold voltage is 0.6V. Output Voltage Sense Input (MP28114DG-1.5, MP28114DG-1.8 and MP28114DG-3.3). An internal resistor divider is connected to this pin to set the proper output voltage. Ground. Connect exposed pad to GND plane for optimal thermal performance. Supply Input. Bypass to GND with a 2.2µF or greater ceramic capacitor. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 4 MP28114 – ULTRA-SMALL 1.7mHz, 600mA LOW-VOLTAGE SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS VIN = 3.3V, VOUT = 1.8V, L1 = 10µH, C1 = 4.7µF, C3 = 10µF, TA = +25°C, unless otherwise noted. 100 1.85 90 90 1.83 80 80 1.81 70 60 50 40 30 70 60 50 40 30 20 20 10 10 0 0 100 LOAD CURRENT (mA) 1000 10 100 LOAD CURRENT (mA) 1.75 1.73 1.71 1.69 1.65 1000 80 80 70 60 50 40 30 Output Voltage vs Supply Voltage 60 50 40 30 20 10 10 0 0 100 LOAD CURRENT (mA) 1000 1.810 70 20 10 100 LOAD CURRENT (mA) 1000 PFET CURRENT LIMIT (A) 0.610 0.605 0.600 0.595 0.590 0.585 0.580 -50 -30 -10 10 30 40 70 90 110 130 1.806 1.804 1.802 1.800 1.2 1.1 1.0 0.9 0.8 0.7 -50 -30 -10 10 30 40 70 90 110 130 2 3 4 5 SUPPLY VOLTAGE (V) 6 Oscillator Frequency vs Supply Voltage PFET Current Limit vs Temperature 1.3 0.615 1.808 ILOAD = 200mA Regulated FB Voltage vs Temperature 0.620 0 100 200 300 400 500 600 700 800 900 LOAD CURRENT (mA) OUTPUT VOLTAGE (V) 90 EFFICIENCY (%) EFFICIENCY (%) 100 90 MP28114 Rev.0.92 8/5/2010 1.77 Efficiency vs Load Current 100 10 1.79 1.67 OSCILLATOR FREQUENCY (MHz) 10 OUTPUT VOLTAGE (V) 100 Efficiency vs Load Current REGULATED FB VOLTAGE (V) Output Voltage vs Load Current Efficiency vs Load Current EFFICIENCY (%) EFFICIENCY (%) Efficiency vs Load Current 2.05 1.95 1.85 1.75 1.65 1.55 1.45 1.35 1.25 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 SUPPLY VOLTAGE (V) www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 5 MP28114 – ULTRA-SMALL 1.7mHz, 600mA LOW-VOLTAGE SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 3.3V, VOUT = 1.8V, L1 = 10µH, C1 = 4.7µF, C3 = 10µF, TA = +25°C, unless otherwise noted. Load Transient Light Load Operation Heavy Load Operation VIN = 3.3V, VOUT = 1.8V, ILOAD = 0 - 500mA Step VIN = 3.3V, VOUT = 1.8V, ILOAD = 0A VIN = 3.3V, VOUT = 1.8V, ILOAD = 600mA MP28114 Rev.0.92 8/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 6 MP28114 – ULTRA-SMALL 1.7mHz, 600mA LOW-VOLTAGE SYNCHRONOUS STEP-DOWN CONVERTER OPERATION The MP28114 is a constant frequency current mode PWM step-down converter. The MP28114 is optimized for low voltage, Li-Ion battery powered applications where high efficiency and small size are critical. The MP28114 uses an external resistor divider to set the output voltage from 0.6V to 6V. The device integrates both a main switch and a synchronous rectifier, which provides high efficiency and eliminates an external Schottky diode. The MP28114 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 (1.7MHz), VOUT is the output voltage and VIN is the input voltage. IN EN ICS 0.6V FB + IAMP 10X -CURRENT SENSE AMP BIAS & VOLTAGE REFERENCE + FEEDBACK ERROR EAMP AMP -- CC 17pF SLOPE COMP EAO + + PWMCMP PWM DH MAIN SWITCH (PCH) -- 1.7MHz OSCILLATOR OSC PWM CONTROL LOGIC SW SYNCHRONOUS RECTIFIER (NCH) DL GND Figure 1—Functional Block Diagram (MP28114) MP28114 Rev.0.92 8/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 7 MP28114 – ULTRA-SMALL 1.7mHz, 600mA LOW-VOLTAGE SYNCHRONOUS STEP-DOWN CONVERTER IN EN ICS 0.6V SLOPE COMP + OUT + IAMP 10X -CURRENT SENSE AMP BIAS & VOLTAGE REFERENCE FEEDBACK ERROR EAMP AMP -- CC 17pF EAO + + PWMCMP PWM DH MAIN SWITCH (PCH) -- 1.7MHz OSCILLATOR OSC PWM CONTROL LOGIC SW SYNCHRONOUS RECTIFIER (NCH) DL GND Figure 2—Functional Block Diagram (MP28114DG-1.5 MP28114DG-1.8/ MP28114DG-3.3) 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 MP28114 switches at a constant frequency (1.7MHz) 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 and stay on until either the next cycle starts. Dropout Operation The MP28114 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 MP28114 Rev.0.92 8/5/2010 to the PFET current limit. The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. Short Circuit Protection The MP28114 has short circuit protection. When the output is shorted to ground, the oscillator frequency is reduced to prevent the inductor current from increasing beyond the PFET current limit. The PFET current limit is also reduced to lower the short circuit current. The frequency and current limit will return to the normal values once the short circuit condition is removed and the feedback voltage reaches 0.6V. Maximum Load current The MP28114 can operate down to 2.5V input voltage, however the maximum load current decreases at lower input due to large IR drop on 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. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 8 MP28114 – ULTRA-SMALL 1.7mHz, 600mA LOW-VOLTAGE SYNCHRONOUS STEP-DOWN CONVERTER APPLICATION INFORMATION Output Voltage Setting (MP28114DG) The external resistor divider sets the output voltage (see Figure 3). The feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor (see Figure 1). Choose R1 around 300kΩ for optimal transient response. R2 is then given by: R2 = R1 VOUT −1 0 .6 V Table 1—Resistor Selection vs. Output Voltage Setting current is recommended for most applications. For best efficiency, the inductor DC resistance shall be <200mΩ. See Table 2 for recommended inductors and manufacturers. For most designs, the inductance value can be derived from the following equation: L= VOUT × (VIN − VOUT ) VIN × ∆IL × fOSC Where ∆IL is the inductor ripple current. Choose inductor ripple current approximately 30% of the maximum load current, 600mA. The maximum inductor peak current is: IL(MAX ) = ILOAD + VOUT R1 R2 1.8V 300kΩ (1%) 150kΩ (1%) 2.5V 300kΩ (1%) 95.3kΩ (1%) Inductor Selection A 1µH to 10µH inductor with DC current rating at least 25% higher than the maximum load ∆IL 2 Under light load conditions below 100mA, larger inductance is recommended for improved efficiency. Table 3 lists inductors recommended for this purpose. Table 2—Suggested Surface Mount Inductors Manufacturer Part Number Inductance (µH) Max DCR (Ω) Saturation Current (A) Dimensions LxWxH (mm3) Coilcraft Toko Taiyo Yuden LP1704-222M D312C LBC2518 2.2 2.2 2.2 0.07 0.14 0.13 1.7 1.0 0.6 6.5x5.3x2 3.6x3.6x1 2.5x1.8x1.8 Table 3—Inductors for Improved Efficiency at 25mA, 50mA, under 100mA Load. Manufacturer Part Number Inductance (µH) Max DCR (Ω) Saturation Current (A) IRMS (A) Coilcraft Murata DO1605T-103MX LQH4C100K04 10 10 0.3 0.2 1.0 1.2 0.9 0.8 Input Capacitor Selection The input capacitor reduces the surge current drawn from the input and 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. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most applications, a 4.7µF capacitor is sufficient. MP28114 Rev.0.92 8/5/2010 Output Capacitor Selection The output capacitor keeps output voltage ripple small and ensures regulation loop stable. The output capacitor impedance shall be low at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended. The output ripple ∆VOUT is approximately: ∆VOUT ≤ ⎞ VOUT × (VIN − VOUT ) ⎛ 1 ⎟ × ⎜⎜ ESR + ⎟ VIN × fOSC × L 8 × f × C 3 OSC ⎠ ⎝ www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 9 MP28114 – ULTRA-SMALL 1.7mHz, 600mA LOW-VOLTAGE SYNCHRONOUS STEP-DOWN CONVERTER PCB LAYOUT GUIDE PCB layout is very important to achieve stable operation. It is highly recommended to duplicate EVB layout for optimum performance. If change is necessary, please follow these guidelines and take Figure 3 for reference. 1) Keep the path of switching current short and minimize the loop area formed by Input cap, high-side MOSFET and low-side MOSFET. 2) Bypass ceramic capacitors are suggested to be put close to the Vin Pin. 3) Place the external feedback resistors as close to the FB pin as possible. 4) Route SW away from sensitive analog areas such as FB. 5) Connect IN, SW, and especially GND respectively to a large copper area to cool the chip to improve thermal performance and long-term reliability. For the fixed output versions (MP28114DG-1.5, MP28114-1.8, and MP28114DG-3.3), R1 is shorted and R2 is open. INPUT 2.5V to 6.0V 7 SW IN 1 OUTPUT L1 R1 MP28114 C1 4 EN GND FB C2 5 R2 6,8 MP28114 Typical Application Circuit FB 5 R1 VIN 4 EN GND 6 3 7 2 IN SGND SGND R2 GND 8 1 SW L1 C1 C2 PGND OUT TOP Layer Bottom Layer Figure 3—MP28114 Typical Application Circuit and PCB Layout Guide MP28114 Rev.0.92 8/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 10 MP28114 – ULTRA-SMALL 1.7mHz, 600mA LOW-VOLTAGE SYNCHRONOUS STEP-DOWN CONVERTER PACKAGE INFORMATION 2mm x 2mm QFN8 PIN 1 ID MARKING 1.90 2.10 0.25 0.45 0.18 0.30 1.90 2.10 PIN 1 ID INDEX AREA PIN 1 ID SEE DETAIL A 0.45 0.65 8 1 1.05 1.25 0.50 BSC 5 TOP VIEW 4 BOTTOM VIEW 0.80 1.00 PIN 1 ID OPTION A R0.20 TYP. PIN 1 ID OPTION B R0.20 TYP. 0.20 REF 0.00 0.05 SIDE VIEW DETAIL A NOTE: 1.90 0.70 0.60 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 VCCD-3. 5) DRAWING IS NOT TO SCALE. 0.25 1.20 0.50 RECOMMENDED LAND PATTERN 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. MP28114 Rev. 0.92 8/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 11