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TM
MP2360
1.8A, 24V, 1.4MHz Step-Down Converter
The Future of Analog IC Technology
TM
DESCRIPTION
The MP2360 is a monolithic step-down switch mode converter with a built-in internal power MOSFET. It achieves 1.8A continuous output current over a wide input supply range with excellent load and line regulation. Current mode operation provides fast transient response and eases loop stabilization. Fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. The MP2360 requires a minimum number of readily available standard external components. The MP2360 is available in a 2mm x 2mm QFN8 package.
FEATURES
* * * * * * * * * * * * * * * * 2.5A Peak Output Current 1.8A Continuous Output Current 0.3 Internal Power MOSFET Switch Stable with Low ESR Output Ceramic Capacitors 0.1A Shutdown Mode Fixed 1.4MHz Frequency Thermal Shutdown Cycle-by-Cycle Over Current Protection Wide 4.5V to 24V Operating Input Range Output Adjustable from 0.81V to 15V Available in 2x2 QFN8 Packages Broadband Communications Equipment Digital Entertainment Systems Distributed Power Systems Battery Charger Pre-Regulator for Linear Regulators
EVALUATION BOARD REFERENCE
Board Number EV2360DG-00B Dimensions 1.8"X x 1.6"Y x 0.4"Z
APPLICATIONS
"MPS" and "The Future of Analog IC Technology" are Trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
Efficiency vs Load Current
VIN
3 IN BST 7
100
MP2360
OFF ON
4 EN
SW
EFFICIENCY (%)
2
CB 10nF D1 B230A VOUT 3.3V
90 80 70 60
VOUT = 3.3V VOUT = 2.5V
GND 6
FB
5
VIN = 12V
50 0 0.5 1.0 1.5 2.0
LOAD CURRENT (A)
MP2360 Rev. 0.9 8/21/2006
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TM
MP2360 - 1.8A, 24V, 1.4MHz STEP-DOWN CONVERTER
PACKAGE REFERENCE
TOP VIEW NC SW IN EN 1 2 3 4 QFN8 (2mm x 2mm) 8 7 6 5 NC BST GND FB
ABSOLUTE MAXIMUM RATINGS (1)
Supply Voltage VIN ....................................... 26V VSW....................................... -0.3V to VIN + 0.3V VBS ....................................................... VSW + 6V All Other Pins................................. -0.3V to +6V Junction Temperature...............................150C Lead Temperature ....................................260C Storage Temperature ..............-65C to +150C
Recommended Operating Conditions
(2)
Supply Voltage VIN ........................... 4.5V to 24V Output Voltage VOUT ...................... 0.81V to 15V Operating Temperature .............-40C to +85C
Thermal Resistance
Part Number* MP2360DG * Package 2x2 QFN8 Temperature -40C to +85C
(3)
2x2 QFN8 ............................... 80 ...... 16... 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.
JA
JC
For Tape & Reel, add suffix -Z (eg. MP2360DG-Z) For RoHS compliant packaging, add suffix -LF (eg. MP2360DG-LF-Z)
ELECTRICAL CHARACTERISTICS
VIN = 12V, TA = +25C, unless otherwise noted.
Parameters Feedback Voltage Feedback Current Switch On-Resistance Switch Leakage Current Limit (4) Oscillator Frequency Fold-back Frequency Maximum Duty Cycle Minimum On-Time (4) Under-Voltage Lockout Threshold Rising Under-Voltage Lockout Threshold Hysteresis EN Input Low Voltage EN Input High Voltage EN Input Current Supply Current (Shutdown) Supply Current (Quiescent) Thermal Shutdown (4)
Note: 4) Guaranteed by design.
(4)
Symbol Condition VFB IFB RDS(ON) VEN = 0V, VSW = 0V Duty Cycle = 40% VFB = 0.6V VFB = 0V VFB = 0.6V 4.5V VIN 24V VFB = 0.8V
Min 0.790
Typ 0.810 10 0.3 0 2.5 1.4 460 87 100 2.8 150
Max 0.830
Units V nA A A MHz KHz % ns V mV V V A
10
2.0
fSW
tON 2.5
3.1 0.4
1.2 VEN = 2V VEN = 0V VEN = 0V VEN = 2V, VFB = 1V 2.1 0.01 0.1 0.8 150
1.0 1.0
A mA C
MP2360 Rev. 0.9 8/21/2006
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TM
MP2360 - 1.8A, 24V, 1.4MHz STEP-DOWN CONVERTER
PIN FUNCTIONS
Pin # 1, 8 2 3 4 5 Name Description NC SW IN EN FB No Connect. Switch Output. Supply Voltage. The MP2360 operates from a +4.5V to +24V unregulated input. C1 is needed to prevent large voltage spikes from appearing at the input. On/Off Control Input. Pull above 1.2V to turn the device on. Feedback. An external resistor divider from the output to GND, tapped to the FB pin sets the output voltage. To prevent current limit run away during a short circuit fault condition the frequency foldback comparator lowers the oscillator frequency when the FB voltage is below 250mV. Ground. This pin is the voltage reference for the regulated output voltage. For this reason care must be taken in its layout. This node should be placed outside of the D1 to C1 ground path to prevent switching current spikes from inducing voltage noise into the part. Bootstrap. This capacitor is needed to drive the power switch's gate above the supply voltage. It is connected between SW and BST pins to form a floating supply across the power switch driver.
6
GND
7
BST
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 3.3V, TA = +25C, unless otherwise noted.
Efficiency vs Load Current
100 VOUT = 5V 90
EFFICIENCY (%)
100
Efficiency vs Load Currents
4.0 VOUT = 12V 90
EFFICIENCY (%)
Current Limit vs Duty Cycle
3.5
CURRENT LIMIT (A)
80 70 60 50 VIN = 12V 40 0 0.5 1.0 1.5 2.0 LOAD CURRENT (A) 2.5 VOUT = 2.5V
80 70 60 50
VOUT = 5V VOUT = 2.5V
3.0 2.5 2.0 1.5 1.0 0.5
VIN = 24V 40 0 0.5 1.0 1.5 2.0 LOAD CURRENT (A) 2.5
0
0
20
40 60 80 DUTY CYCLE (%)
100
MP2360 Rev. 0.9 8/21/2006
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TM
MP2360 - 1.8A, 24V, 1.4MHz STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, VOUT = 3.3V, TA = +25C, unless otherwise noted.
Steady State Test
VIN = 12V, VOUT = 3.3V, IOUT = 0.5A
Load Transient Test
VIN = 12V, VOUT = 3.3V
VOUT 20mV/div.
VOUT AC Coupled 200mV/div.
VSW 10V/div.
IL 1A/div. ILOAD 1A/div.
IL 500mA/div.
400ns/div.
Start-up through Enable
VIN = 12V, VOUT = 3.3V, No Load
Start-up through Enable
VIN = 12V, VOUT = 3.3V, IOUT = 2A Resistive Load
VEN 5V/div. VOUT 2V/div. VSW 10V/div. IL 2A/div. VEN 5V/div. VOUT 2V/div.
Shut-down through Enable
VIN = 12V, VOUT = 3.3V, No Load
VEN 5V/div. VOUT 2V/div. VSW 10V/div. IL 2A/div.
VSW 10V/div.
IL 2A/div.
Shut-down through Enable
VIN = 12V, VOUT = 3.3V, IOUT = 2A Resistive Load
VEN 5V/div. VOUT 2V/div. VSW 10V/div. IL 2A/div. IL 2A/div. VOUT 2V/div.
Short Circuit Entry
VIN = 12V, VOUT = 3.3V
Short Circuit Recovery
VIN = 12V, VOUT = 3.3V
VOUT 2V/div.
IL 2A/div.
MP2360 Rev. 0.9 8/21/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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TM
MP2360 - 1.8A, 24V, 1.4MHz STEP-DOWN CONVERTER
OPERATION
The MP2360 is a current mode buck regulator. That is, the EA output voltage is proportional to the peak inductor current. At the beginning of a cycle, M1 is off. The EA output voltage is higher than the current sense amplifier output, and the current comparator's output is low. The rising edge of the 1.4 MHz CLK signal sets the RS Flip-Flop. Its output turns on M1 thus connecting the SW pin and inductor to the input supply. The increasing inductor current is sensed and amplified by the Current Sense Amplifier. Ramp compensation is summed to Current Sense Amplifier output and compared to the Error Amplifier output by the PWM Comparator. When the sum of the Current Sense Amplifier output and the Slope Compensation signal exceeds the EA output voltage, the RS FlipFlop is reset and the M1 is turned off. The external Schottky rectifier diode (D1) conducts the inductor current. If the sum of the Current Sense Amplifier output and the Slope Compensation signal does not exceed the EA output for a whole cycle, then the falling edge of the CLK resets the Flip-Flop. The output of the Error Amplifier integrates the voltage difference between the feedback and the 0.81V bandgap reference. The polarity is such that a FB pin voltage lower than 0.8V increases the EA output voltage. Since the EA output voltage is proportional to the peak inductor current, an increase in its voltage also increases current delivered to the output.
IN D x20
CURRENT SENSE AMPLIFIER
REGULATOR
EN
REGULATOR
OSCILLATOR 1.4MHz
S + -1pF
CURRENT LIMIT COMPARATOR
Q
R R SW
REFERENCE
27pF +EA -+ --
FB GND
ERROR AMPLIFIER
PWM COMPARATOR
Figure 1--Functional Block Diagram
MP2360 Rev. 0.9 8/21/2006
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+ -BST
DRIVER
M1
5
TM
MP2360 - 1.8A, 24V, 1.4MHz STEP-DOWN CONVERTER
APPLICATION INFORMATION
Setting Output Voltage The external resistor divider is used to set the output voltage (see the schematic on front page). The feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor (see Figure 1). R2 can be determined by:
R2 = R1 VOUT -1 0.81V
Table 1--Resistor Selection for Common Output Voltages
VOUT (V) 1.8 2.5 3.3 5 R1 (k) 80.6 (1%) 49.9 (1%) 49.9 (1%) 49.9 (1%) R2 (k) 64.9 (1%) 23.7 (1%) 16.2 (1%) 9.53 (1%)
Selecting the Input Capacitor 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 should be less than the input source impedance to prevent high frequency switching current from passing through 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 10F capacitor is sufficient. Selecting the Output Capacitor The output capacitor keeps output voltage ripple small and ensures loop stability. The output capacitor impedance should be low at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended for their low ESR characteristics. For most applications, a 22F ceramic capacitor will be sufficient. PC Board Layout The high current paths (GND, IN and SW) should be placed very close to the device with short, direct and wide traces. The input capacitor needs to be as close as possible to the IN and GND pins. The external feedback resistors should be placed next to the FB pin. Keep the switch node traces short and away from the feedback network. External Bootstrap Diode It is recommended that an external bootstrap diode be added when the input voltage is no greater than 5V or the 5V rail is available in the system. This helps improve the efficiency of the regulator. The bootstrap diode can be a low cost one such as IN4148 or BAT54.
5V (External) or VIN (4.5 to 5V)
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Selecting the Inductor A 1H to 10H inductor with a DC current rating of at least 25% percent higher than the maximum load current is recommended for most applications. For highest efficiency, the inductor's DC resistance should be less than 200m. For most designs, the required inductance value can be derived from the following equation.
L= VOUT x ( VIN - VOUT ) VIN x IL x f OSC
Where IL is the inductor ripple current. Choose an inductor with a rating current of approximately 30% higher than the maximum load current if the maximum load current is 1.8A. The maximum inductor peak current is calculated from:
IL(MAX ) = ILOAD I +L 2
BST
MP2360
SW 2
10nF
Under light load conditions below 100mA, a larger inductance is recommended for improved efficiency. See Table 2 for suggested inductors.
Figure 2--External Bootstrap Diode This diode is also recommended for high duty cycle operation (when
VOUT >65%) applications. VIN
MP2360 Rev. 0.9 8/21/2006
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TM
MP2360 - 1.8A, 24V, 1.4MHz STEP-DOWN CONVERTER Table 2--Suggested Surface Mount Inductors
Manufacturer Wurth Electronics Toko Coiltronics
Part Number 7447785004 A916CY-4R7M DR73-4R7
Inductance(H) 4.7 4.7 4.7
Max DCR() 0.060 0.026 0.03
Current Rating (A) 2.5 2.5 3
Dimensions L x W x H (mm3) 5.9 x 6.2 x 3.3 6.2 x 6.3 x 3.5 6.0 x 7.6 x 3.5
TYPICAL APPLICATION CIRCUIT
VIN
3 IN BST 7
C4 10nF OFF ON
4 EN
MP2360
SW
2
D1 B230A
5
VOUT 3.3V
GND 6
FB
Figure 3--1.4MHz, 3.3V Output Step-Down Converter
MP2360 Rev. 0.9 8/21/2006
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TM
MP2360 - 1.8A, 24V, 1.4MHz STEP-DOWN CONVERTER
PACKAGE INFORMATION
2mm x 2mm QFN8
PIN 1 ID MARKING 1.90 2.10 0.18 0.30 1.90 2.10 0.50 BSC 0.25 0.45 8 0.45 0.65 PIN 1 ID SEE DETAIL A 1 1.05 1.25
PIN 1 ID INDEX AREA
5
4
TOP VIEW
BOTTOM VIEW
0.80 1.00 0.20 REF 0.00 0.05
PIN 1 ID OPTION A R0.20 TYP.
PIN 1 ID OPTION B R0.20 TYP.
SIDE VIEW
DETAIL A
1.90 0.70 0.25 0.60
NOTE:
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. 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.
MP2360 Rev. 0.9 8/21/2006 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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