MPS MP2360 1.8a, 24v, 1.4mhz step-down converter Datasheet

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.
FEATURES
•
•
•
•
2.5A Peak Output Current
1.8A Continuous Output Current
0.3Ω Internal Power MOSFET Switch
Stable with Low ESR Output Ceramic
Capacitors
0.1µA 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
The MP2360 requires a minimum number of
readily available standard external components.
The MP2360 is available in a 2mm x 2mm QFN8
package.
•
•
•
•
•
•
•
EVALUATION BOARD REFERENCE
APPLICATIONS
Board Number
Dimensions
EV2360DG-00B
1.8”X x 1.6”Y x 0.4”Z
•
•
•
•
•
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 Trademarks of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
Efficiency vs
Load Current
3
IN
BST
MP2360
OFF ON
4
EN
GND
6
SW
100
7
2
CB
10nF
D1
B230A
FB
5
VOUT = 3.3V
90
VOUT
3.3V
EFFICIENCY (%)
VIN
VOUT = 2.5V
80
70
60
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
ABSOLUTE MAXIMUM RATINGS (1)
PACKAGE REFERENCE
Supply Voltage VIN ....................................... 26V
VSW....................................... –0.3V to VIN + 0.3V
VBS ....................................................... VSW + 6V
All Other Pins................................. –0.3V to +6V
Junction Temperature...............................150°C
Lead Temperature ....................................260°C
Storage Temperature ..............–65°C to +150°C
TOP VIEW
NC
1
8
NC
SW
2
7
BST
IN
3
6
GND
EN
4
5
FB
Recommended Operating Conditions
Supply Voltage VIN ........................... 4.5V to 24V
Output Voltage VOUT ...................... 0.81V to 15V
Operating Temperature .............–40°C to +85°C
QFN8
(2mm x 2mm)
Thermal Resistance
(3)
θJA
θJC
2x2 QFN8 ............................... 80 ...... 16... °C/W
Part Number*
Package
Temperature
MP2360DG
2x2 QFN8
–40°C to +85°C
*
(2)
For Tape & Reel, add suffix –Z (eg. MP2360DG–Z)
For RoHS compliant packaging, add suffix –LF (eg.
MP2360DG–LF–Z)
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
VIN = 12V, TA = +25°C, unless otherwise noted.
Parameters
Symbol Condition
Feedback Voltage
Feedback Current
(4)
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)
VFB
4.5V ≤ VIN ≤ 24V
IFB
VFB = 0.8V
Min
Typ
Max
Units
0.790
0.810
0.830
V
RDS(ON)
fSW
VEN = 0V, VSW = 0V
Duty Cycle = 40%
VFB = 0.6V
VFB = 0V
VFB = 0.6V
2.0
tON
2.5
10
nA
0.3
0
2.5
1.4
460
87
100
2.8
150
Ω
µA
A
MHz
KHz
%
ns
V
mV
V
V
10
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
µA
1.0
1.0
µA
mA
°C
Note:
4) Guaranteed by design.
MP2360 Rev. 0.9
8/21/2006
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2
TM
MP2360 – 1.8A, 24V, 1.4MHz STEP-DOWN CONVERTER
PIN FUNCTIONS
Pin #
Name Description
1, 8
2
NC
SW
3
IN
4
EN
5
FB
6
GND
7
BST
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.
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 3.3V, TA = +25°C, unless otherwise noted.
4.0
100
VOUT = 12V
VOUT = 5V
80
VOUT = 2.5V
70
60
50
0
0.5
1.0
1.5
2.0
LOAD CURRENT (A)
MP2360 Rev. 0.9
8/21/2006
VOUT = 5V
80
VOUT = 2.5V
70
60
50
VIN = 12V
40
3.5
90
EFFICIENCY (%)
EFFICIENCY (%)
90
40
0
0.5
1.0
1.5
2.0
LOAD CURRENT (A)
3.0
2.5
2.0
1.5
1.0
0.5
VIN = 24V
2.5
CURRENT LIMIT (A)
100
Current Limit vs
Duty Cycle
Efficiency vs
Load Currents
Efficiency vs
Load Current
2.5
0
0
20
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40
60
80
DUTY CYCLE (%)
100
3
TM
MP2360 – 1.8A, 24V, 1.4MHz STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, VOUT = 3.3V, TA = +25°C, unless otherwise noted.
Load Transient Test
Steady State Test
VIN = 12V, VOUT = 3.3V
VIN = 12V, VOUT = 3.3V, IOUT = 0.5A
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
Start-up through Enable
Shut-down through Enable
VIN = 12V, VOUT = 3.3V,
IOUT = 2A Resistive Load
VIN = 12V, VOUT = 3.3V, No Load
VEN
5V/div.
VEN
5V/div.
VOUT
2V/div.
VOUT
2V/div.
VSW
10V/div.
VSW
10V/div.
IL
2A/div.
IL
2A/div.
Shut-down through Enable
VIN = 12V, VOUT = 3.3V, No Load
VEN
5V/div.
VOUT
2V/div.
VSW
10V/div.
IL
2A/div.
Short Circuit Recovery
Short Circuit Entry
VIN = 12V, VOUT = 3.3V,
IOUT = 2A Resistive Load
VIN = 12V, VOUT = 3.3V
VIN = 12V, VOUT = 3.3V
VEN
5V/div.
VOUT
2V/div.
VOUT
2V/div.
VOUT
2V/div.
VSW
10V/div.
IL
2A/div.
MP2360 Rev. 0.9
8/21/2006
IL
2A/div.
IL
2A/div.
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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
x20
CURRENT SENSE
AMPLIFIER
+
--
D
REGULATOR
BST
EN
REGULATOR
OSCILLATOR
1.4MHz
S
+
-1pF
REFERENCE
FB
Q
DRIVER
M1
R
CURRENT
LIMIT
COMPARATOR
R
SW
27pF
+EA
--
ERROR
AMPLIFIER
+
--
PWM
COMPARATOR
GND
Figure 1—Functional Block Diagram
MP2360 Rev. 0.9
8/21/2006
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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)
R1 (kΩ)
R2 (kΩ)
1.8
2.5
3.3
5
80.6 (1%)
49.9 (1%)
49.9 (1%)
49.9 (1%)
64.9 (1%)
23.7 (1%)
16.2 (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
200mΩ. For most designs, the required
inductance value can be derived from the
following equation.
L=
VOUT × ( VIN − VOUT )
VIN × ∆IL × 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
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.
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)
BST
7
10nF
MP2360
SW
2
Figure 2—External Bootstrap Diode
This diode is also recommended for high duty cycle
operation (when
MP2360 Rev. 0.9
8/21/2006
VOUT
>65%) applications.
VIN
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TM
MP2360 – 1.8A, 24V, 1.4MHz STEP-DOWN CONVERTER
Table 2—Suggested Surface Mount Inductors
Manufacturer
Part Number
Inductance(µH)
Max DCR(Ω)
Current Rating
(A)
Dimensions
L x W x H (mm3)
Wurth Electronics
Toko
Coiltronics
7447785004
A916CY-4R7M
DR73-4R7
4.7
4.7
4.7
0.060
0.026
0.03
2.5
2.5
3
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
GND
SW
2
D1
B230A
FB
VOUT
3.3V
5
6
Figure 3—1.4MHz, 3.3V Output Step-Down Converter
MP2360 Rev. 0.9
8/21/2006
www.MonolithicPower.com
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© 2006 MPS. All Rights Reserved.
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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
0.25
0.45
0.18
0.30
1.90
2.10
PIN 1 ID
INDEX AREA
PIN 1 ID
SEE DETAIL A
0.45
0.65
8
1
1.05
1.25
0.50
BSC
5
TOP VIEW
4
BOTTOM VIEW
0.80
1.00
PIN 1 ID OPTION A
R0.20 TYP.
PIN 1 ID OPTION B
R0.20 TYP.
0.20 REF
0.00
0.05
SIDE VIEW
DETAIL A
NOTE:
1.90
0.70
0.60
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.
0.25
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.
© 2006 MPS. All Rights Reserved.
8
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