MP2115 2A Synchronous Step-Down Converter with Programmable Input Current Limit The Future of Analog IC Technology DESCRIPTION FEATURES The MP2115 is a high frequency, current mode, PWM step-down converter with integrated input current limit switch. The step-down converter integrates a main switch and a synchronous rectifier for high efficiency without an external Schottky diode. The input average current limit can be externally programmed. It is ideal for powering portable equipment that is powered by an USB port. The MP2115 can supply 2A of load current from a 2.8V to 6V input voltage. The output voltage can be regulated as low as 0.6V. • • • • • • • • • • • • The MP2115 is available in a space-saving 10-pin QFN package. High Efficiency: Up to 92% Programmable Switching Frequency from 0.7MHz-2MHz Programmable Input Current Limit 2A Available Load Current 2.8V to 6V Input Voltage Range Output Voltage as Low as 0.6V Current Mode Control Power Good Indicator Short Circuit Protection Thermal Fault Protection <0.1µA Shutdown Current Space Saving 3mm x 3mm QFN10 Package APPLICATIONS • • • • • • • USB Powered Devices Cellular and Smart Phones Microprocessors and DSP Core Supplies PDAs MP3 Players Digital Still and Video Cameras Portable Instruments For MPS green status, please visit MPS website under Quality Assurance. “MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION USB Input R4 R3 10 EN 5 4 AGND 6TPE470MI x 3 R6 86.6k 6 PGND MP2115DQ VSYS 2 ILIM 8 PG VIN FREG VSYS 100 EN 100k U1 1 Efficiency PG 100k R5 24.9k SW FB 3.8V/2A 7 3 VOUT=3.8V, Freq=1.5MHz VIN=5.0V 90 9 R1 51k R2 9.53k C5 220pF VOUT EFFICIENCY (%) VIN VIN=5.5V 80 70 60 50 0.0 0.1 0.2 0.3 0.4 0.5 0.6 LOAD CURRENT ( A ) MP2115 Rev. 1.0 2/28/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 1 MP2115 – 2A, 6V SYNCHRONOUS STEP-DOWN CONVERTER ORDERING INFORMATION Part Number* MP2115DQ Package QFN10 (3mm x 3mm) Top Marking Free Air Temperature (TA) 2X -40°C to +85°C * For Tape & Reel, add suffix –Z (e.g. MP2115DQ–Z). For RoHS compliant packaging, add suffix –LF (e.g. MP2115DQ–LF–Z) PACKAGE REFERENCE TOP VIEW VIN 1 10 PG ILIM 2 9 EN FB 3 8 VSYS GND 4 7 SW FREQ 5 6 PGND EXPOSED PAD ON BACKSIDE CONNECT TO GND 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, PG, VSYS, ILIM to GND ...............................................-0.3V to +6.5V Continuous Power Dissipation (TA = +25°C) (2) ............................................................. 2.5W Junction Temperature ............................ +150°C Lead Temperature ................................. +260°C Storage Temperature .............. -65°C to +150°C QFN10 (3x3) ........................... 50 ...... 12... °C/W Recommended Operating Conditions (3) Supply Voltage VIN ............................. 2.8V to 6V Output Voltage VOUT ........................... 0.6V to 6V Maximum Junction Temp. (TJ) ............... +125°C MP2115 Rev. 1.0 2/28/2011 (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 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) 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. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 2 MP2115 – 2A, 6V SYNCHRONOUS STEP-DOWN CONVERTER ELECTRICAL CHARACTERISTICS (5) VIN = VEN = 5.0V, TA = +25°C, unless otherwise noted. Parameter Supply Current Shutdown Current IN Undervoltage Lockout Threshold IN Undervoltage Lockout Hysteresis Symbol Condition VEN = VIN, VFB = 0.65V VEN = 0V, VIN = 6V Rising Edge Min 2.2 Max 1000 1 2.45 FB Input Bias Current PFET On Resistance ISW = 100mA 0.1 Ω NFET On Resistance Load Switch PFET On Resistance Load Switch Current Set ISW = -100mA 0.1 0.22 500 Ω Ω mA VFB RILIM=25kΩ VEN = 0V, VIN = 6V, VSW = 0V or 6V SW Leakage Current PFET Current Limit（6） Oscillator Frequency -1 +1 3.5 fOSC RFREQ = 100kΩ 1.05 Thermal Shutdown Trip Threshold EN Input Low Voltage En Input High Voltage EN Input Current Power Good Ramp Up Threshold Power Good Ramp Down Threshold Soft Start Time Power Good Sink Current Capability Power Good Leakage Current 0.619 0.625 +50 Units µA µA V mV TA = +25°C -40°C ≤ TA ≤ +85°C VFB = 0.65V Regulated FB Voltage 0.595 0.589 -50 Typ 800 0.10 2.35 60 0.607 0.607 0.5 VIN = 0V to 6V C5=220pF VPG IPG LEAK Sink 4mA VPG = 3.3V nA µA A 1.3 1.55 145 0.3 1.65 -1 V 1.32 1.75 1.45 2 1 80 70 100 -50 0.5 50 MHz °C V V µA % % µs V nA Note: 5) 100% production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization. 6）Guaranteed by design MP2115 Rev. 1.0 2/28/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 3 MP2115 – 2A, 6V SYNCHRONOUS STEP-DOWN CONVERTER PIN FUNCTIONS Pin # Name 1 2 VIN ILIM 3 FB 4 AGND 5 FREQ 6 7 8 9 10 Description Supply Input for the power stage. Input Current Limit setting pin. A resistor from this pin to ground sets the input current limit. Feedback Input. Connect FB to the center point of the external resistor divider. The feedback threshold voltage is 0.6V. Analog Ground. Switching Frequency Program Input. Connect a resistor from this pin to ground to set the switching frequency. PGND Exposed The exposed pad and PGND pin must be connected to the same ground plane. Pad SW Power Switch Output. Inductor connection to drains of the internal PFET and NFET switches. Load switch output and switching regulator input. Usually this pin connects to a large tantalum VSYS capacitor as energy reservoir. EN On/Off Control Input. Power good signal. When FB is less than 80% of 0.6V, PG is low. It is an open-drain output. PG Use a high value pull-up resistor externally to pull it up to system power supply. MP2115 Rev. 1.0 2/28/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 4 MP2115 – 2A, 6V SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS C1=10µF, C2=470µFx3, C4=220µF, C5=220pF, L= 4.7µH, TA = +25°C, unless otherwise noted. Efficiency vs. Load Current VOUT = 3.8V, Freq=1.5MHz 3.870 VIN=5.0V VIN=5.5V 80 70 60 50 0.0 0.1 0.2 0.3 0.4 0.5 3.868 3.866 3.864 3.862 3.860 0.0 0.6 LOAD CURRENT (A) SWITCHING FREQUENCY (MHz) 60 50 40 30 20 10 0.28 0.36 0.44 144 30 108 20 72 10 36 0.1 0.2 0.3 0.4 0.5 -36 -20 -72 -30 -108 -40 -144 -180 1000 -50 0.6 0.52 0 -10 0.1 0.6 100 VFB vs. Temperature VIN = 5V 0.65 2.0 0.62 1.6 1.2 0.8 0.4 10 1 FREQUENCY (kHz) FSW vs. Resistor 70 0.2 180 40 LOAD CURRENT (A) ILIMIT Resistor vs. Input Current 0 50 0 VINVOLTAGE(Y) 90 Loop Gain with Phase Margin VIN = 5V, VOUT = 3.8V, IOUT = 0.5A OUTPUT VOLTAGE (V) EFFICIENCY (%) 100 Load Regulation 0.59 0.56 0.53 0.50 - 40 - 20 50 100 150 200 250 300 350 400 0 20 40 60 80 100 INPUT CURRENT (A) Transient Response FSW vs. Temperature VIN = 5V, VOUT = 3.8V, IOUT = 0.7A/4.66ms IOUT 1A/div. MP2115 Rev. 1.0 2/28/2011 VOUT 0.1V/div. IOUT 0.5A/div. 1.35 SWITCHING FREQUENCY (MHz) VOUT 0.1V/div. VIN = 5V 1.34 1.33 1.32 1.31 1.30 -40 -20 0 20 40 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 60 80 100 5 MP2115 – 2A, 6V SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (continued) C1=10µF, C2=470µFx3, C4=220µF, C5=220pF, L= 4.7µH, TA = +25°C, unless otherwise noted. Steady State Power Ramp Up Power Ramp Down VIN = 5V, VEN put to VIN, VOUT = 3.8V, IOUT = 0.5A, Freq = 2MHz VIN = 5V, VEN put to VIN, VOUT = 3.8V, IOUT = 0.5A VIN = 5V, VEN put to VIN, VOUT = 3.8V, IOUT = 0.5A VSYS 5V/div. VSYS 5V/div. VPG 5V/div. VSYS 5V/div. VPG 5V/div. VOUT 2V/div. VOUT 2V/div. IOUT 0.5A/div. IOUT 0.5A/div. VSW 5V/div. VOUT 2V/div. IL 0.5A/div. Steady State Enable Up Enable Down VIN = 5V, VEN put to VIN, VOUT = 3.8V, IOUT = 0.5A, Freq = 0.7MHz VIN = 5V, VEN = 0-2V, VOUT = 3.8V, IOUT = 0.5A, Resistor Load VIN = 5V, VEN = 2-0V, VOUT = 3.8V, IOUT = 0.5A, Resistor Load VSYS 5V/div. VSW 5V/div. VOUT 2V/div. IL 0.5A/div. VEN 2V/div. VEN 2V/div. VSW 5V/div. VSW 5V/div. VOUT 2V/div. VOUT 2V/div. IOUT 0.5A/div. IOUT 0.5A/div. Short Circuit Short Circuit Recovery VIN = 5V, VEN put to VIN, VOUT = 3.8V VIN = 5V, VEN put to VIN, VOUT = 3.8V 0.5A VOUT 2V/div. VOUT 2V/div. IL 5A/div. IL 2A/div. MP2115 Rev. 1.0 2/28/2011 IIN 0.1A/div. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 6 MP2115 – 2A, 6V SYNCHRONOUS STEP-DOWN CONVERTER FUNCTIONAL BLOCK DIAGRAM VSYS ILIM FB VIN X10 EN Input Current Limit Control Bias & Voltage Refernce SLOP COMP + EAO EAMP + BG ICS 0.6V PG + - + + PWM COMP PWM - GND DH - FB CC 17pF FREQ OSCILLATOR ICS 3.5A + LIM PWM Control Logic RZ 1M OSC SW DL ILIM PGND AGND GND Figure 1—Functional Block Diagram MP2115 Rev. 1.0 2/28/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 7 MP2115 – 2A, 6V SYNCHRONOUS STEP-DOWN CONVERTER OPERATION The MP2115 is a constant frequency current mode PWM step-down converter. The MP2115 is optimized for low voltage, USB port and LiIon battery powered applications where high efficiency and small size are critical. The MP2115 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 MP2115 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, and fOSC is the oscillator frequency. 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. This protects the internal main switch and synchronous rectifier. The MP2115 switch is programmable from 0.7MHz to 2MHz. 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, then switched off when the peak inductor current rises above the error voltage. When the main switch is off, the synchronous rectifier will turn on immediately and stay on until the next cycle starts. Dropout Operation The MP2115 allows the main switch to remain on for more than one switching cycle and increases the duty cycle when the input voltage drops close to the output voltage. When the duty cycle reaches 100%, the main switch continuously delivers current to the output up to the PFET current limit. The output voltage is the input voltage minus the voltage drop across the main switch and the inductor. MP2115 Rev. 1.0 2/28/2011 Short Circuit Protection The MP2115 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 MP2115 can operate down to a 2.8V input voltage; however the maximum load current decreases at lower input due to a 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. Programmable Input Current Limit The MP2115 has an input current limit protection function. It will insure that the input current doesn't exceed the maximum, when the input is supplied by the USB. Once the input current triggers the set current limit level, the output voltage will shut down and latch off until the input is reset. The input current limit resistor R5 value can be found from Table 1. Table 1—Resistor Selection vs. Input Current Setting VIN (V) VOUT (V) 5 3.8 IOUT (A) 0.2 0.3 0.4 0.45 0.5 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. R5 (kΩ) 47.2 33.3 25.75 23.29 24.9 8 MP2115 – 2A, 6V SYNCHRONOUS STEP-DOWN CONVERTER APPLICATION INFORMATION Output Voltage Setting The external resistor divider sets the output voltage (see Typical Application Circuit on page 1). The feedback resistor (R1) also sets the feedback loop bandwidth with the internal compensation capacitor (see Figure 1-Function Block Diagram). Inductor Selection A 1µH to 10µH 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 <200mΩ. See Table 3 for recommended inductors and manufacturers. For most designs, the inductance value can be derived from the following equation: Choose R1 around 500kΩ for optimal transient response. R2 is then given by: R2 = L1 = VOUT × (VIN − VOUT ) VIN × ∆IL × fOSC R1 VOUT −1 0. 6 V Table 2—Resistor Selection vs. Output Voltage Setting Where ∆IL is the Inductor Ripple Current. Choose inductor ripple current approximately 30% of the maximum load current, 2.5A. The maximum inductor peak current is: IL(MAX ) = ILOAD + VOUT R1 R2 1.2V 1.5V 1.8V 2.5V 3.8V 51kΩ (1%) 51kΩ (1%) 51kΩ (1%) 51kΩ (1%) 51kΩ (1%) 51kΩ (1%) 34kΩ (1%) 25.5kΩ (1%) 16kΩ (1%) 9.53Ω(1%) ∆IL 2 Under light load conditions below 100mA, larger inductance is recommended for improved efficiency. Table 4 lists inductors recommended for this purpose. Table 3—Suggested Surface Mount Inductors Manufacturer Part Number Inductance (µH) Max DCR (Ω) Coilcraft Toko Sumida D63CB D53LC CDC5D23B 4.7 4.7 4.7 0.026 0.026 0.062 Saturation Current (A) 2 2 1.6 Dimensions LxWxH (mm3) 6.3X6.3X3.5 6.3X6.3X3.5 6.0X6.0X2.5 Table 4—Inductors for Improved Efficiency at 25mA, 50mA, under 100mA Load. Manufacturer Part Number Inductance (µH) Max DCR (Ω) Coilcraft Murata Sumida Sumida DO1605T-103MX LQH4C100K04 CR32-100 CR54-100 10 10 10 10 0.3 0.2 0.2 0.1 MP2115 Rev. 1.0 2/28/2011 Saturation Current (A) 1.0 1.2 1.0 1.2 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. IRMS (A) 0.9 0.8 0.7 1.4 9 MP2115 – 2A, 6V SYNCHRONOUS STEP-DOWN CONVERTER Input Capacitor Selection The input capacitor (C1) reduces the surge current drawn from the input and switching noise from the device. The input capacitor impedance at the switching frequency must 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 10µF capacitor is sufficient. Output Capacitor Selection The output capacitor (C4) keeps output voltage ripple small and ensures regulation loop stable. The output capacitor impedance should remain 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 × f OSC × L 8 × f × C 2 OSC ⎝ ⎠ VSYS Capacitor Selection The VSYS capacitor C2 is used to supply the USB port and with the peak output current, such as during the TDM frame. That output peak current is about 2A. Use three 470µF capacitors to avoid large voltage drops. MP2115 Rev. 1.0 2/28/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 10 MP2115 – 2A, 6V SYNCHRONOUS STEP-DOWN CONVERTER PACKAGE INFORMATION QFN10 (3mm x 3mm) NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications. 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. MP2115 Rev. 1.0 2/28/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 11