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PDF MP28265 Data sheet ( Hoja de datos )
| Número de pieza | MP28265 | |
| Descripción | 1.1MHz Synchronous Step-down Converter | |
| Fabricantes | MPS | |
| Logotipo |  |
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The Future of Analog IC Technology
MP28265
21V, 5A, 1.1MHz
Synchronous Step-down Converter
DESCRIPTION
The MP28265 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 5A continuous
output current over a wide input supply range
with excellent load and line regulation. The
MP28265 operates at high efficiency over a
wide 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 MP28265 requires a minimum number of
readily available standard external components
and is available in a space saving 3mm x 4mm
14-pin QFN package.
FEATURES
• Wide 4.5V to 21V Operating Input Range
• 5A Output Current
• Low RDS(ON) Internal Power MOSFETs
• Proprietary Switching Loss Reduction
Technique
• Fixed 1.1MHz Switching Frequency
• Sync from 400kHz to 2MHz External Clock
• Internal Compensation
• OCP Protection and Thermal Shutdown
• Output Adjustable from 0.8V
• Available in 14-pin QFN3x4 Package
APPLICATIONS
• Notebook Systems and I/O Power
• Networking Systems
• Digital Set Top Boxes
• Personal Video Recorders
• Flat Panel Television and Monitors
• Distributed Power Systems
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
The information in this datasheet about the product and its associated
technologies are proprietary and intellectual property of Monolithic Power
Systems and are protected by copyright and pending patent applications
TYPICAL APPLICATION （FOR NOTEBOOK）
4.5V-21V
VIN
1 IN
BST 6
PG
ON/OFF
9 PG
R3
100K11 VCC
MP28265
7 EN/SYNC
SW 2,3,4,5
8
FB
NC GND AGND
10 12,13 14
Rt
24.9K
R1
4.99K
R2
10K
Efficiency
VOUT=1.2V
100
90 VIN=5V
80
VIN=12V
70
60 VIN=21V
50
40
30
20
10
0
012345
OUTPUT CURRENT(A)
6
MP28265 Rev. 0.92
12/2/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
1
1 page  
MP28265 – 5A, 21V, SYNCHRONOUS STEP-DOWN CONVERTER WITH INTERNAL MOSFETS
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 1.2V, L = 0.95µH, TA = +25ºC, unless otherwise noted.
Enable Supply Current
vs. Input Voltage
VFB=1V
1000
950
900
850
800
750
700
650
600
550
500
0
5 10 15 20 25
INPUT VOLTAGE (V)
Disable Supply Current
vs. Input Voltage
VEN=0V
0.2
0.15
0.1
0.05
0
-0.05
-0.1
-0.15
-0.2
0
5 10 15 20
INPUT VOLTAGE (V)
25
VCC Regulator Line Regulation
6
5.5
5
4.5
4
3.5 0
5 10 15 20
INPUT VOLTAGE (V)
25
Peak Current vs. Duty Cycle Operating Range
7
6.8
6.6
6.4
6.2
6
5.8
5.6
5.4
5.2
5
0 10 20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)
100
10
1
0.1
0
Dmax Limit
Minimum on Time Limit
5 10 15 20
INPUT VOLTAGE (V)
25
Load Regulation
1
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
0
VIN=4.5V
VIN=12V
VIN=21V
1234
LOAD CURRENT(A)
5
Line Regulation
1
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
0
IOUT=0A
IOUT=2.5A
IOUT=5A
5 10 15 20
INPUT VOLTAGE (V)
25
Case Tem perature Rise
vs.Output Current
60
50
40
30
20
10
0
01234
OUTPUT CURRENT (A)
5
MP28265 Rev. 0.92
12/2/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
5
5 Page 
MP28265 – 5A, 21V, SYNCHRONOUS STEP-DOWN CONVERTER WITH INTERNAL MOSFETS
APPLICATION INFORMATION
Setting the Output Voltage
The external resistor divider is used to set the
output voltage (see Typical Application on page
1). The feedback resistor R1 also sets the
feedback loop bandwidth with the internal
compensation capacitor (see Typical Application
on page 1). Choose R1 to be around 40.2kΩ for
optimal transient response. R2 is then given by:
R2 = R1
VOUT − 1
VFB
The T-type network is highly recommended when
Vo is low, as Figure 6 shows.
FB 1
Rt
R1
VOUT
R2
Figure 6— T-type Network
Table 1 lists the recommended T-type resistors
value for common output voltages.
Table 1—Resistor Selection for Common
Output Voltages
VOUT (V)
1.05
1.2
1.5
1.8
2.5
3.3
5
R1 (kΩ)
4.99(1%)
4.99(1%)
4.99(1%)
4.99(1%)
40.2 (1%)
40.2(1%)
40.2 (1%)
R2 (kΩ)
16.5(1%)
10.2(1%)
5.76(1%)
4.02(1%)
19.1(1%)
13(1%)
7.68(1%)
Rt (kΩ)
24.9(1%)
24.9(1%)
24.9(1%)
24.9(1%)
0
0
0
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
DC resistance should be less than 15mΩ. For
most designs, the inductance value can be
derived from the following equation.
L
=
VOUT × (VIN − VOUT )
VIN × ΔIL × fOSC
Where ΔIL is the inductor ripple current.
Choose inductor ripple current to be
approximately 30% if the maximum load current,
5A. The maximum inductor peak current is:
IL(MAX)
= ILOAD
+
ΔIL
2
Under light load conditions below 100mA, larger
inductance is recommended for improved
efficiency.
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:
IC1 = ILOAD ×
VOUT
VIN
×⎜⎜⎛1−
⎝
VOUT
VIN
⎟⎞
⎟
⎠
The worse case condition occurs at VIN = 2VOUT,
where:
IC1
=
ILOAD
2
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:
ΔVIN
=
ILOAD
fS × C1
×
VOUT
VIN
× ⎜⎜⎝⎛1 −
VOUT
VIN
⎟⎟⎠⎞
MP28265 Rev. 0.92
12/2/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet MP28265.PDF ] | |
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