TM MP28117 Dual 1.2MHz, 800mA Synchronous Step-Down Converter The Future of Analog IC Technology TM DESCRIPTION FEATURES The MP28117 contains two independent 1.2MHz constant frequency, current mode, PWM step-down converters. Each converter integrates a main switch and a synchronous rectifier for high efficiency without an external Schottky diode. The MP28117 is ideal for powering portable equipment that runs from a single cell Lithium-Ion (Li+) battery. Each converter can supply 800mA of load current from a 2.5V to 6V input voltage. The output voltage can be regulated as low as 0.6V. The MP28117 can also run at 100% duty cycle for low dropout applications. * * * * * * * * * * * * Up to 95% Efficiency 1.2MHz Constant Switching Frequency 800mA Load Current on Each Channel 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 <0.1A Shutdown Current Internally Compensated Space Saving 10-Pin QFN Package APPLICATIONS * * * * * * 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 Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION VIN1/IN2 2.5V to 6V VOUT1 1.8V 800mA 1 10 2 3 IN2 EN1 EN2 MP28117 SW1 SW2 FB1 FB2 GND1 9 MP28117 Rev.1.0 12/13/2007 100 GND2 4 6 5 7 95 OFF ON VOUT2 1.2V 800mA 90 EFFICIENCY (%) OFF ON 8 IN1 VOUT=3.3V 85 80 75 70 65 60 55 50 0 500 LOAD CURRENT (mA) www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2007 MPS. All Rights Reserved. 1000 1 TM MP28117 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER ABSOLUTE MAXIMUM RATINGS (1) PACKAGE REFERENCE TOP VIEW EN1 1 10 SW1 FB1 2 9 GND1 IN2 3 8 IN1 GND2 4 7 FB2 SW2 5 6 EN2 EXPOSED PAD ON BACKSIDE Part Number* Package Temperature MP28117DQ QFN10 (3mm x 3mm) -40C to +85C * For Tape & Reel, add suffix -Z (eg. MP28117DQ-Z) For RoHS Compliant Packaging, add suffix -LF (eg. MP28117DQ-LF-Z) VIN1/IN2 to GND ............................ -0.3V to +6.5V VSW1/SW2 to GND................... -0.3V to VIN + 0.3V VFB1/FB2, VEN1/EN2 to GND ............. -0.3V to +6.5V Junction Temperature.............................+150C Lead Temperature ..................................+260C Storage Temperature .............-65C to +150C Recommended Operating Conditions (2) Supply Voltage VIN1/IN2 ....................... 2.5V to 6V Output Voltage VOUT1/OUT2 .................. 0.6V to 6V Operating Temperature .............-40C to +85C Thermal Resistance (3) JA JC QFN10 (3mm x 3mm) ............. 50 ...... 12... C/W Notes: 1) Exceeding these ratings may damage the device. 2) The device is not guaranteed to function outside of its operating conditions. 3) Measured on approximately 1" square of 1 oz copper. ELECTRICAL CHARACTERISTICS (4) VIN1/IN2 = VEN1/EN2 = 3.6V, TA = +25C, unless otherwise noted. Parameter Symbol Condition Each Converter Supply Current VEN1/EN2 = VIN1/IN2, VFB1/FB2 = 0.65V Each Converter Shutdown VEN1/EN2 = 0V, VIN1/IN2 = 6V Current IN Under Voltage Lockout Rising Edge Threshold IN Under Voltage Lockout Hysteresis TA = +25C Regulated FB Voltage VFB -40C TA +85C FB Input Bias Current IFB VFB1/FB2 = 0.65V PFET On Resistance ISW1/SW2 = 100mA NFET On Resistance ISW1/SW2 = -100mA VEN1/EN2 = 0V, VIN1/IN2 = 6V SW Leakage Current VSW1/SW2 = 0V or 6V Duty Cycle = 100%, PFET Current Limit Current Pulse Width < 1ms Oscillator Frequency fOSC Thermal Shutdown Trip Threshold EN Enable Threshold -40C TA +85C EN Input Current VEN1/EN2 = 0V to 6V Min 2.15 Typ 440 Max 600 Units A 0.10 1 A 2.30 2.40 V 55 0.588 0.582 -50 0.600 0.600 0.5 0.42 0.26 -2 mV 0.612 0.618 +50 V nA +2 A 0.9 1.3 1.8 A 0.99 1.24 1.49 MHz C 150 0.3 -1 0.96 1.5 +1 V A Notes: 4) Production test at +25C. Specifications over the temperature range are guaranteed by design and characterization. MP28117 Rev.1.0 12/13/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2007 MPS. All Rights Reserved. 2 TM MP28117 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS VIN1/IN2 = 3.3V, VOUT1 = 1.8V, VOUT2 = 1.2V, L1/2 = 4.7H, CIN1/IN2 = 4.7F, COUT1/OUT2 = 10F, TA = +25C, unless otherwise noted. Efficiency vs Load Current 100 0.606 FEEDBACK VOLTAGE (V) VOUT1=1.8V EFFICIENCY (%) 90 VOUT2=1.2V 80 70 60 50 0.0 0.2 0.4 0.6 LOAD CURRENT (A) Feedback Voltage vs Temperature 0.604 0.602 0.600 0.598 0.596 0.594 -40 -20 0.8 0 +20 +40 +60 +80 +100 TEMPERATURE (C) Load Transient Medium Load Operation Heavy Load Operation (IOUT=0mA to 500mA Step) (IOUT=400mA) (IOUT=800mA) VOUT AC 100mV/div. IL 0.5A/div. VSW 2V/div. VSW 2V/div. VOUT AC 20mV/div. VOUT AC 20mV/div. IL 200mA/div. ILOAD 0.5A/div. IL 500mA/div. 400ns/div Startup from Shutdown VEN 2V/div VOUT 1V/div IL 0.5A/div MP28117 Rev.1.0 12/13/2007 400ns/div Short Circuit Protection Short Circuit Recovery (No Load) (No Load) VOUT 1V/div VOUT 1V/div IL 0.5A/div IL 0.5A/div www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2007 MPS. All Rights Reserved. 3 TM MP28117 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER PIN FUNCTIONS Pin # 1 2 3 4 5 6 7 8 9 10 Name Description Channel 1 Enable Control Input. Drive EN1 above 1.5V to turn on the Channel 1. Drive EN1 below 0.3V to turn it off (shutdown current < 0.1A). Channel 1 Feedback Input. Connect FB1 to the center point of the external resistor divider. The FB1 feedback voltage is 0.6V. IN2 Channel 2 Supply Input. Bypass to GND with a 2.2F or greater ceramic capacitor. GND2 Ground 2. Channel 2 Power Switch Output. Inductor connection to drains of the internal PFET and NFET SW2 switches. Channel 2 Enable Control Input. Drive EN2 above 1.5V to turn on the Channel 2. Drive EN2 EN2 below 0.3V to turn it off (shutdown current < 0.1A). Channel 2 Feedback Input. Connect FB2 to the center point of the external resistor divider. The FB2 feedback voltage is 0.6V. IN1 Channel 1 Supply Input. Bypass to GND with a 2.2F or greater ceramic capacitor. GND1 Ground 1. Channel 1 Power Switch Output. Inductor connection to drains of the internal PFET and NFET SW1 switches. EN1 MP28117 Rev.1.0 12/13/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2007 MPS. All Rights Reserved. 4 TM MP28117 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER OPERATION IN1/ IN2 EN1/ EN2 ICS 0.6V SLOPE COMP + FB1/ FB2 + IAMP 10X -CURRENT SENSE AMP BIAS & VOLTAGE REFERENCE FEEDBACK ERROR\ EAMP AMP -- CC 17pF EAO + + PWMCMP PWM DH MAIN SWITCH (PCH) -- 1.0MHz OSCILLATOR OSC SW1/ SW2 PWM CONTROL LOGIC SYNCHRONOUS RECTIFIER (NCH) DL GND1/ GND2 Figure 1--Functional Block Diagram (Diagram represents 1/2 of the MP28117) The MP28117 has dual independent constant frequency current mode PWM step-down converters. The MP28117 is optimized for low voltage, Li-Ion battery powered applications where high efficiency and small size are critical. The MP28117 uses external resistor dividers to set two output voltages independently from 0.6V to 6V. The device integrates both main switches and synchronous rectifiers, which provides high efficiency and eliminates the need for an external Schottky diode. The MP28117 can achieve 100% duty cycle. The duty cycle D of each step-down converter is defined as: D = TON x f OSC x 100% = VOUT x 100% VIN Where TON is the main switch on time, fOSC is the oscillator frequency (1.2MHz), VOUT is the output voltage and VIN is the input voltage. MP28117 Rev.1.0 12/13/2007 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. Each channel switches at a constant frequency (1.2MHz) 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 the next cycle starts. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2007 MPS. All Rights Reserved. 5 TM MP28117 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER Dropout Operation Each channel of the MP28117 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 PFET current limit. The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. Maximum Load Current The MP28117 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. Short Circuit Protection The MP28117 has short circuit protection. When any 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. APPLICATION INFORMATION Output Voltage Setting The external resistor divider sets the output voltage. The feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor (see Figure 1). Choose R1 around 300k for optimal transient response. R2 is then given by: R2 = R1 VOUT -1 0 .6 V L= Table 1--Resistor Selection vs. Output Voltage Setting VOUT R1 R2 1.2V 300k (1%) 300k (1%) 1.5V 300k (1%) 200k (1%) 1.8V 300k (1%) 150k (1%) 2.5V 300k (1%) 95.3k (1%) MP28117 Rev.1.0 12/13/2007 Inductor Selection A 1H to 10H 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 <200m. See Table 2 for recommended inductors and manufacturers. For most designs, the inductance value can be derived from the following equation: VOUT x (VIN - VOUT ) VIN x IL x fOSC Where IL is inductor ripple current. Choose inductor ripple current approximately 30% of the maximum load current, 800mA. The maximum inductor peak current is: IL(MAX ) = ILOAD + IL 2 Under light load conditions below 100mA, larger inductance is recommended for improved efficiency. Table 3 lists inductors recommended for this purpose. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2007 MPS. All Rights Reserved. 6 TM MP28117 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER Table 2--Suggested Surface Mount Inductors Manufacturer Part Number Inductance (H) Max DCR () Saturation Current (A) Dimensions LxWxH (mm3) Coilcraft Toko Sumida LP03310-222ML 1002AS CDRH3D16 2.2 2.2 2.2 0.15 0.11 0.072 1.1 1.14 1.20 3.3 x 3.3 x 1 4.6 x 4.6 x 1.2 4 x 4 x 1.8 Table 3--Inductors for Improved Efficiency at 25mA, 50mA, under 100mA Load. Manufacturer Part Number Inductance (H) Max DCR () Saturation Current (A) IRMS (A) Coilcraft Murata Sumida Sumida DO1605T-103MX LQH4C100K04 CR32-100 CR54-100 10 10 10 10 0.3 0.2 0.2 0.1 1.0 1.2 1.0 1.2 0.9 0.8 0.7 1.4 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 4.7F capacitor is sufficient. 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 x (VIN - VOUT ) 1 x ESR + VIN x f OSC x L 8 x f OSC x C3 MP28117 Rev.1.0 12/13/2007 Thermal Dissipation Power dissipation shall be considered when both channels of the MP28117 provide maximum 800mA output current to the loads at high ambient temperature with low input supply voltage. If the junction temperature rises above 150C, the MP28117 two channels will be shut down. The junction-to-ambient thermal resistance of the 10-pin QFN (3mm x 3mm) RJA is 50C/W. The maximum power dissipation is about 1.6W when the MP28117 is operating in a 70C ambient temperature environment. PD MAX = 150 o C - 70 o C 50 o C / W = 1 .6 W PC Board Layout The high current paths (GND1/GND2, IN1/IN2 and SW1/SW2) should be placed very close to the device with short, direct and wide traces. Input capacitors should be placed as close as possible to the respective IN and GND pins. The external feedback resistors shall be placed next to the FB pins. Keep the switching nodes SW1/SW2 short and away from the feedback network. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2007 MPS. All Rights Reserved. 7 TM MP28117 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER PACKAGE INFORMATION QFN10 (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. 0.80 1.00 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 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. MP28117 Rev. 1.0 12/13/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2007 MPS. All Rights Reserved. 8