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High Efficiency 2A, 24V, 500kHz Synchronous Step Down Converter MP2314 Rev. 1.02 www.MonolithicPower.com 1 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. The Future of Analog IC Technology
DESCRIPTION
The MP2314 is a high frequency synchronous rectified step-down switch mode converter with built in internal power MOSFETs. It offers a very compact solution to achieve 2A continuous output current over a wide input supply range with excellent load and line regulation. The MP2314 has synchronous mode operation for higher efficiency over output current load range. Current mode operation provides fast transient response and eases loop stabilization. Full protection features include OCP and thermal shut down. The MP2314 requires a minimum number of readily available standard external components and is available in a space saving 8-pin TSOT23 package.
FEATURES
Wide 4.5V to 24V Operating Input Range 2A Load Current 120m Ω/50mΩ Low Rds(on) Internal Power MOSFETs Low Quiescent Current High Efficiency Synchronous Mode Operation Fixed 500kHz Switching Frequency Frequency Sync from 200kHz to 2MHz External Clock AAM Power Save Mode Internal Soft Start OCP Protection and Hiccup Thermal Shutdown Output Adjustable from 0.8V Available in an 8-pin TSOT-23 package
APPLICATIONS
Notebook Systems and I/O Power Digital Set Top Boxes Flat Panel Television and Monitors All MPS parts are lead-free and adhere to the RoHS directive. For MPS green status, please visit MPS website under Products, Quality Assurance page. “MPS” and “The Future of Analog IC Technology” are registered trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION 100 0.01 0.1 1 10
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 2 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved.
ORDERING INFORMATION
Part Number* Package Top Marking MP2314GJ TSOT23-8 AEL * For Tape & Reel, add suffix –Z (e.g. MP2314GJ–Z); PACKAGE REFERENCE AAM IN SW GND FB VCC EN/SYNC BST TOP VIEW TSOT23-8 ABSOLUTE MAXIMUM RATINGS (1) Continuous Power Dissipation (TA=+25°C) (2) ... Recommended Operating Conditions (3) Operating Junction Temp (TJ).. -40°C to +125°C Thermal Resistance (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 T J (MAX), the junction-to- ambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by P D (MAX) = (T J (MAX)-TA)/θJA. Exceeding the maximum allowable powe r 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.
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 3 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved.
ELECTRICAL CHARACTERISTICS
VIN = 12V, TA = 25°C, unless otherwise noted. Parameter Symbol Condition Min Typ Max Units Supply Current (Shutdown) IIN V EN = 0V 1 μA Supply Current (Quiescent) Iq VEN = 2V, V FB = 1V, AAM=0.5V 130 180 240 μA HS Switch On Resistance HS RDS-ON V BST-SW=5V 120 m Ω LS Switch On Resistance LS RDS-ON V CC=5V 50 m Ω Switch Leakage SW LKG V EN = 0V, VSW =12V 1 μA Current Limit I LIMIT Duty Cycle=40% 3 4 A Oscillator Frequency f SW V FB=750mV 420 500 620 kHz Fold-back Frequency f FB V FB=200mV 0.5 f SW Maximum Duty Cycle D MAX V FB=750mV 90 95 % Minimum On Time (5) T ON_MIN 60 ns Sync Frequency Range f SYNC 0.2 2 MHz TA=25°C 779 791 803 mV Feedback Voltage V FB -40°C<TA <85°C(6) 775 791 807 mV Feedback Current I FB V FB=820mV 10 50 nA EN Rising Threshold V EN_RISING 1.2 1.4 1.6 V EN Hysteresis V EN_HYS 80 150 220 mV VEN=2V 1.5 2 2.5 μA EN Input Current I EN VEN=0 0 50 nA EN Turn Off Delay EN Td-off 6 10 14 μs VIN Under Voltage Lockout Threshold-Rising INUVVth 3.7 3.9 4.1 V VIN Under Voltage Lockout Threshold- Hysteresis INUV HYS 550 650 750 mV VCC Regulator V CC 4.65 4.9 5.15 V VCC Load Regulation I CC=5mA 0 1 3 % Soft-Start Period T SS V O from 10% to 90% 0.8 1.5 2.2 ms Thermal Shutdown(5) 150 ºC Thermal Hysteresis(5) 20 ºC AAM Source Current I AAM 5.6 6.2 6.8 μA Notes: 5) Guaranteed by design. 6) Not tested in production and guaranteed by over-temperature correlation.
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 4 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. TYPICAL CHARACTERISTICS -1.5 -0.5 0.5 1.5 0 0.5 1 1.5 2 -1.5 -0.5 0.5 1.5 6 8 10 12 14 16 18 20 22 24 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 0 1 02 03 04 05 06 07 08 09 0 158 159 160 161 162 163 164 165 166 167 168 4 9 14 19 24 100 0.01 0.1 1 10 100 0.01 0.1 1 10 100 0.01 0.1 1 10 100 0.01 0.1 1 10 100 0.01 0.1 1 10
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 5 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. TYPICAL CHARACTERISTICS (continued) 0 5 10 15 20 25 30 0.786 0.787 0.788 0.789 0.79 0.791 0.792 -40 -20 0 20 40 60 80 100120140
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 6 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. TYPICAL PERFORMANCE CHARACTERISTICS VIN = 19V, VOUT = 5V, L = 6.5uH, TA = 25°C, unless otherwise noted. VOUT/AC 20mV/div. VIN/AC 200mV/div. VSW 10V/div. IL 2A/div. VOUT/AC 20mV/div. VIN/AC 500mV/div. VSW 10V/div. IL 1A/div. VOUT 2V/div. VIN 10V/div. VSW 10V/div. IL 1A/div. VOUT 2V/div. VIN 10V/div. VSW 10V/div. IL 2A/div. VOUT 2V/div. VEN 5V/div. VSW 10V/div. IL 2A/div. VOUT 2V/div. VEN 5V/div. VSW 10V/div. IL 5A/div. VOUT 2V/div. VEN 5V/div. VSW 10V/div. IL 2A/div. VOUT 2V/div. VIN 10V/div. VSW 10V/div. IL 2A/div. VOUT 2V/div. VIN 10V/div. VSW 10V/div. IL 1A/div.
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 7 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 19V, VOUT = 5V, L = 6.5µH, TA = 25°C, unless otherwise noted. VOUT/AC 50mV/div. IO 1A/div. VOUT 2V/div. VEN 5V/div. VSW 10V/div. IL 1A/div.
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 8 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. PIN FUNCTIONS Package Pin # Name Description
1 AAM
A resistor is connected from AAM pin to ground to set a AAM voltage force MP2314 into non-synchronous mode when load is small. Driv e AAM pin high (=VCC) or float AAM pin will disable AAM mode and force MP2314 into CCM. 2 IN Supply Voltage. The MP2314 operates from a +4.5V to +24V input rail. C1 is needed to decouple the input rail. Use wide PCB trace to make the connection. 3 SW Switch Output. Use wide PC B trace to make the connection.
4 GND
System Ground. This pin is the reference ground of the regulated output voltage. For this reason care must be taken in PCB layout. Suggested to be connected to GND with copper and vias. 5 BST Bootstrap. A capacitor and a 20 Ω resistor connected between SW and BST pins are required to form a floating supply across the high-side switch driver. 6 EN/SYNC EN=1 to enable the MP2314. External clock can be applied to EN pin for changing switching frequency. 7 VCC Bias Supply. Decouple with 0.1 μF-0.22μF cap. And the capacitance should be no more than 0.22μF 8 FB Feedback. An external resistor divider from the output to GND, tapped to the FB pin, sets the output voltage. To prevent current limit r un away during a short circuit fault condition the frequency fold-back comparator lowers th e oscillator frequency when the FB voltage is below 400mV.
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 9 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. FUNCTION BLOCK DIAGRAM Figure 1: Functional Block Diagram
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 10 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. OPERATION The MP2314 is a high frequency synchronous rectified step-down switch mode converter with built in internal power MOSFETs. It offers a very compact solution to achieve 2A continuous output current over a wide input supply range with excellent load and line regulation. When MP2314 operates in fixed frequency peak current control mode to regulate the output voltage, the PWM cycle is initiated by the internal clock. The integrated high-side power MOSFET is turned on and remains on until its current reaches the value set by the COMP voltage. When the power switch is off, it remains off until the next clock cycle starts. If, in 95% of one PWM period, the current in the power MOSFET does not reach the COMP set current value, the power MOSFET will be forced to turn off. Internal Regulator Most of the internal circuitries are powered from the 5V internal regulator. This regulator takes the VIN input and operates in the full VIN range. When VIN is greater than 5.0V, the output of the regulator is in full regulation. When VIN is lower than 5.0V, the output decreases, a 0.1uF ceramic capacitor for decoupling purpose is required. Error Amplifier The error amplifier compares the FB pin voltage with the internal 0.791V reference (REF) and outputs a COMP voltage, which is used to control the power MOSFET current. The optimized internal compensation network minimizes the external component counts and simplifies the control loop design. AAM Operation The MP2314 has AAM (Advanced Asynchronous Modulation) power-save mode for light load. Connect a resistor from AAM pin to GND to set AAM voltage. Under the heavy load condition, the V COMP is higher than V AAM. When the clock goes high, the high-side power MOSFET turns on and remains on until V ILsense reaches the value set by the COMP voltage. The internal clock resets every time when V COMP is higher than VAAM. Under the light load condition, the value of VCOMP is low. When V COMP is less than V AAM and VFB is less than V REF, V COMP ramps up until it exceeds V AAM. During this time, the internal clock is blocked, thus the MP2314 skips some pulses for PFM (Pulse Frequency Modulation) mode and achieves the light load power save. Figure 2: Simplified AAM Control Logic To enable AAM mode, connect a resistor from AAM pin to GND. To disable AAM mode, connect AAM to Vcc or float AAM pin the converter will always operate in fixed frequency CCM mode. Enable/SYNC control EN is a digital control pin that turns the regulator on and off. Drive EN high to turn on the regulator, drive it low to turn it off. There is an internal 1MEG resistor from EN to GND thus EN can be floated to shut down the chip. Also EN pin voltage was clamped to around 6.5V by an internal zener-diode. Please use large enough pull up resistor connecting between VIN and EN to limit the EN input current which should be less than 100uA. Generally, around 100k resistor should be large enough for all the applications. The chip can be synchronized to external clock range from 200kHz up to 2MHz through this pin 2ms right after output voltage is set, with the internal clock rising edge synchronized to the external clock rising edge. EN synchronize logic high voltage should higher than 2V. EN synchronize logic low voltage should lower than 400mV. EN logic high pulse width must less than 1.6µs. Otherwise the internal clock may come and turn on high side MOSFET again. EN logic low pulse width must less than 6µs, otherwise MP2314 may EN shutdown.
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 11 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. Under-Voltage Lockout (UVLO) Under-voltage lockout (UVLO) is implemented to protect the chip from operating at insufficient supply voltage. The MP2314 UVLO comparator monitors the output voltage of the internal regulator, VCC. The UVLO rising threshold is about 3.9V while its falling threshold is consistent 3.25V. Pre-Bias Startup The MP2314 has been designed for monotonic startup into pre-biased loads. If the output is pre-biased to a certain voltage during startup, the BST voltage will be refreshed and charged. If BST voltage exceeds its rising threshold voltage and soft start voltage exceeds the sensed output voltage at the FB pin, the part starts to work normally. Internal Soft-Start The soft start is implemented to prevent the converter output voltage from overshooting during start up. When the chip starts, the internal circuitry generates a soft-start voltage (SS) ramping up from 0V. The soft-start period lasts until the voltage on the soft-start capacitor exceeds the reference voltage of 0.791V. At this point the reference voltage takes over. The soft-start time is internally set to be around 1.5ms. Over-Current-Protection and Hiccup The MP2314 has cycle-by-cycle over current limit when the inductor current peak value exceeds the set current limit threshold. Meanwhile, output voltage starts to drop until FB is below the Under-Voltage (UV) threshold, typically 50% below the reference. Once a UV is triggered, the MP2314 enters hiccup mode to periodically restart the part. This protection mode is especially useful when the output is dead-short to ground. The average short circuit current is greatly reduced to alleviate the thermal issue and to protect the regulator. The MP2314 exits the hiccup mode once the over current condition is removed. Thermal Shutdown Thermal shutdown is implemented to prevent the chip from operating at exceedingly high temperatures. When the silicon die temperature is higher than 150°C, it shuts down the whole chip. When the temperature is lower than its lower threshold, typically 130°C, the chip is enabled again. Floating Driver and Bootstrap Charging The floating power MOSFET driver is powered by an external bootstrap capacitor. This floating driver has its own UVLO protection. This UVLO’s rising threshold is 2.2V with a hysteresis of 150mV. The bootstrap capacitor voltage is regulated internally by VIN through D1, R5, C5, L1 and C2 (Figure 3). If (VIN-VSW) is more than 5V, U2 will regulate M3 to maintain a 5V BST voltage across C5. Figure 3: Internal Bootstrap Charging Circuit Startup and Shutdown If both V IN and EN are higher than their appropriate thresholds, the chip starts. The reference block starts first, generating stable reference voltage and currents, and then the internal regulator is enabled. The regulator provides stable supply for the remaining circuitries. Three events can shut down the chip: EN low, VIN low and thermal shutdown. In the shutdown procedure, the signaling path is first blocked to avoid any fault triggering. The COMP voltage and the internal supply rail are then pulled down. The floating driver is not subject to this shutdown command.
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 13 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 0.1 0.2 0.3 0.4 0.5 0.6 0.7 02468 Figure 6: AAM Selection for Common Output Voltages (VIN=4.5V-24V) Selecting the Input Capacitor The input current to the step-down converter is discontinuous, therefore a capacitor is required to supply the AC current to the step-down converter while maintaining the DC input voltage. Use low ESR capacitors for the best performance. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most applications, a 22µF capacitor is sufficient. Since the input capacitor (C1) absorbs the input switching current it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated by: IN OUT IN OUTLOAD1C V V1V VII The worse case condition occurs at VIN = 2VOUT, where: II LOAD 1C For simplification, choose the input capacitor whose RMS current rating greater than half of the maximum load current. The input capacitor can be electrolytic, tantalum or ceramic. When using electrolytic or tantalum capacitors, a small, high quality ceramic capacitor, i.e. 0.1μF, should be placed as close to the IC as possible. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. The input voltage ripple caused by capacitance can be estimated by: LOAD OUT OUT IN INSI N IV VV1 fC 1V V Selecting the Output Capacitor The output capacitor (C2) is required to maintain the DC output voltage. Ceramic, tantalum, or low ESR electrolytic capacitors are recommended. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by: OUT OUT OUT ESR S1 I N S VV 1V1 R fL V 8 fC 2 Where L1 is the inductor value and RESR is the equivalent series resistance (ESR) value of the output capacitor. In the case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance. The output voltage ripple is mainly caused by the capacitance. For simplification, the output voltage ripple can be estimated by: OUT OUT OUT 2 INS1 VVΔV1 V8f L C 2 In the case of tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to: OUT OUT OUT ESR INS1 VVΔV1 R fL V The characteristics of the output capacitor also affect the stability of the regulation system. The MP1495 can be optimized for a wide range of capacitance and ESR values. External Bootstrap Diode An external bootstrap diode may enhance the efficiency of the regulator, the applicable conditions of external BST diode are: VOUT is 5V or 3.3V; and Duty cycle is high: D= IN OUT V V >65%
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER MP2314 Rev. 1.02 www.MonolithicPower.com 15 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. Design Example Below is a design example following the application guidelines for the specifications: Table 2: Design Example VIN 19V VOUT 5V IO 2A The detailed application schematics are shown in Figures 9 through 14. The typical performance and circuit waveforms have been shown in the Typical Performance Characteristics section. For more device applications, please refer to the related Evaluation Board Datasheets.
MP2314 – 24V, 2A SYNC STEP DOWN CONVERTER NOTICE: The information in this document is subject to change wi thout notice. Users should warra nt and guarantee that third party Intellectual Property rights are not infringed upon w hen integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MP2314 Rev. 1.02 www.MonolithicPower.com 18 9/17/2014 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved.