MP2270
1.8A, 24V, 700kHz
Step-Down Converter
MP2270 Rev. 1.1 www.MonolithicPower.com 1
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The Future of Analog IC Technology
DESCRIPTION
The MP2270 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 MP2270 requires a minimum number of
readily available standard external components.
The MP2270 is available in a 10-pin exposed pad
MSOP package.
FEATURES
• 1.8A Continuous Output Current
• 0.3 Internal Power MOSFET Switch
• Stable with Low ESR Output Ceramic
Capacitors
• 0.1A Shutdown Mode
• Fixed 700kHz Frequency
• Thermal Shutdown
• Cycle-by-Cycle Over Current Protection
• Wide 4.5V to 24V Operating Input Range
• Output Adjustable from 0.81V to 20V
• Available in a 10-pin Exposed Pad MSOP
Package
APPLICATIONS
• Broadband Communications Equipment
• Digital Entertainment Systems
• Distributed Power Systems
• Battery Charger
• Pre-Regulator for Linear Regulators
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
MP2270 SW
FB
BST
5
6
8
10
3
1
GND
IN
EN
V
OUT
3.3V
CB
10nF
D1
B230A
V
IN
OFF ON
V
IN
I
OUT_MAX
=1.8
MP2270 – 1.8A, 24V, 700KHz STEP-DOWN CONVERTER
MP2270 Rev. 1.1 www.MonolithicPower.com 2
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ORDERING INFORMATION
Part Number* Package Top Marking Free Air Temperature (TA)
MP2270DH MSOP10w/Exposed Pad 2270D -40°C to +85°C
* For Tape & Reel, add suffix –Z (e.g. MP2270DH–Z).
For RoHS Compliant packaging, add suffix –LF (e.g. MP2270DH–LF–Z)
PACKAGE REFERENCE
EXPOSED PAD
ON BACKSIDE
Connect to GND
BST
N/C
SW
N/C
IN
1
2
3
4
5
10
9
8
7
6
FB
N/C
GND
N/C
EN
TOP VIEW
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
Continuous Power Dissipation (TA = +25°C) (2)
………………………………………………....2.3W
Junction Temperature...............................150°C
Lead Temperature ....................................260°C
Storage Temperature............... -65°C to +150°C
Recommended Operating Conditions (3)
Supply Voltage VIN ...........................4.5V to 24V
Operating Junct. Temp (TJ)...... -40°C to +125°C
Thermal Resistance (4) θJA θJC
MSOP10 w/Exposed Pad .......55 ...... 12... °C/W
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-to-
ambient thermal resistance JA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD (MAX) = (TJ
(MAX)-TA)/JA. 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.
MP2270 – 1.8A, 24V, 700KHz STEP-DOWN CONVERTER
MP2270 Rev. 1.1 www.MonolithicPower.com 3
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© 2010 MPS. All Rights Reserved.
ELECTRICAL CHARACTERISTICS
VIN = 12V, TA = +25°C, unless otherwise noted.
Parameters Symbol Condition Min Typ Max Units
Feedback Voltage VFB 4.5V ≤ VIN ≤ 24V 0.790 0.810 0.830 V
Feedback Current IFB V
FB = 0.8V 10 nA
Switch On-Resistance (5) R
DS(ON) 0.3
Switch Leakage VEN = 0V, VSW = 0V 0 10 A
Current Limit (5) Duty Cycle = 40% 2.0 2.5 A
Oscillator Frequency fSW V
FB = 0.6V 700 kHz
Fold-back Frequency VFB = 0V 230 kHz
Maximum Duty Cycle VFB = 0.6V 87 %
Minimum On-Time (5) t
ON 100 ns
Under-Voltage Lockout Threshold Rising 2.5 2.8 3.1 V
Under-Voltage Lockout Threshold Hysteresis 150 mV
EN Input Low Voltage 0.4 V
EN Input High Voltage 1.5 V
VEN = 2V 2.1
EN Input Current VEN = 0V 0.01 A
Supply Current (Shutdown) VEN = 0V 0.1 1.0 A
Supply Current (Quiescent) VEN = 2V, VFB = 1V 0.8 1.0 mA
Thermal Shutdown (5) 150 °C
Note:
5) Guaranteed by design.
MP2270 – 1.8A, 24V, 700KHz STEP-DOWN CONVERTER
MP2270 Rev. 1.1 www.MonolithicPower.com 4
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PIN FUNCTIONS
Pin # Name Description
2, 4,
9, 7 NC No Connect.
3 SW Switch Output.
5 IN
Supply Voltage. The MP2270 operates from a +4.5V to +24V unregulated input. C1 is needed
to prevent large voltage spikes from appearing at the input.
6 EN On/Off Control Input. Pull above 1.2V to turn the device on.
10 FB
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.
8
GND,
Exposed
pad
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. Exposed
pad must be connected to a ground plane for proper thermal operation.
1 BST
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.
MP2270 – 1.8A, 24V, 700KHz STEP-DOWN CONVERTER
MP2270 Rev. 1.1 www.MonolithicPower.com 5
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TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 1.8V, L=6.8H, ILOAD=0.5A – 1.8A, TA = +20°C, unless otherwise noted.
0 204060 10080
01
5
700
720
740
760
780
800
820
840
860
880
900
10 15 20 0 2052510 15
0 0.5
0
5
10
15
20
25
30
35
40
1.0 1.5 2.0
0
0.5
1.0
1.5
2.5
2.0
3.0
0510152025
D
MAX
Limit
V
OUT_MAX
Minimum On Time Limit
V
FB_MIN
V
IN
=12V
V
IN
=20V
MP2270 – 1.8A, 24V, 700KHz STEP-DOWN CONVERTER
MP2270 Rev. 1.1 www.MonolithicPower.com 6
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© 2010 MPS. All Rights Reserved.
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, VOUT = 1.8V, L=6.8H, ILOAD=0.5A – 1.8A, TA = +20°C, unless otherwise noted.
MP2270 – 1.8A, 24V, 700KHz STEP-DOWN CONVERTER
MP2270 Rev. 1.1 www.MonolithicPower.com 7
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© 2010 MPS. All Rights Reserved.
OPERATION
The MP2270 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 700KHz
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 Flip-
Flop 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
EN
FB
GND
SW
BST
REGULATOR OSCILLATOR
700KHz DRIVER
CURRENT SENSE
AMPLIFIER
ERROR
AMPLIFIER
CURRENT
LIMIT
COMPARATOR
PWM
COMPARATOR
D
x20
M1
REGULATOR
REFERENCE
EA
--
+--
+
--
+
S
R
R
Q
--
+
27pF
1pF
Figure 1—Functional Block Diagram
MP2270 – 1.8A, 24V, 700KHz STEP-DOWN CONVERTER
MP2270 Rev. 1.1 www.MonolithicPower.com 8
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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:
1
V81.0
V
1R
2R
OUT −
=
Table 1—Resistor Selection for Common
Output Voltages
VOUT (V) R1 (k) R2 (k)
1.8 80.6 (1%) 64.9 (1%)
2.5 49.9 (1%) 23.7 (1%)
3.3 49.9 (1%) 16.2 (1%)
5 49.9 (1%) 9.53 (1%)
Selecting the Inductor
A 1µH to 10µH 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.
OSCLIN
OUTINOUT
fIV
)VV(V
L×Δ×
−×
=
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:
2
I
II L
LOAD)MAX(L
Δ
+=
Under light load conditions below 100mA, a
larger inductance is recommended for improved
efficiency. See Table 2 for suggested inductors.
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 10µF 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
22µF 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.
MP2270 – 1.8A, 24V, 700KHz STEP-DOWN CONVERTER
MP2270 Rev. 1.1 www.MonolithicPower.com 9
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External Bootstrap Diode
An external bootstrap diode may enhance the
efficiency of the regulator, the applicable
conditions of external BST diode are:
z VOUT=5V or 3.3V; and
z Duty cycle is high: D=
IN
OUT
V
V>65%
In these cases, an external BST diode is
recommended from the output of the voltage
regulator to BST pin, as shown in Fig.2
MP2270
SW
BST
C
L
BST
C
5V or 3.3V
OUT
External BST Diode
IN4148
Figure 2—Add Optional External Bootstrap
Diode to Enhance Efficiency
The recommended external BST diode is IN4148,
and the BST cap is 0.1~1µF.
Table 2—Suggested Surface Mount Inductors
Manufacturer Part Number Inductance(µH) Max DCR()Current Rating
(A)
Dimensions
L x W x H (mm3)
Wurth Electronics 7447785004 4.7 0.060 2.5 5.9 x 6.2 x 3.3
Toko A916CY-4R7M 4.7 0.026 2.5 6.2 x 6.3 x 3.5
Coiltronics DR73-4R7 4.7 0.03 3 6.0 x 7.6 x 3.5
MP2270 – 1.8A, 24V, 700KHz STEP-DOWN CONVERTER
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.
MP2270 Rev. 1.1 www.MonolithicPower.com 10
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PACKAGE INFORMATION
MSOP 10 (EXPOSED PAD)
