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PDF MP4350 Data sheet ( Hoja de datos )
| Número de pieza | MP4350 | |
| Descripción | Step-Down Converter | |
| Fabricantes | MPS | |
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MP4350
Step-Down
The Future of Analog IC Technology
DESCRIPTION
The MP4350 is a high frequency step-down
switching re gulator with an integrated internal
high-side h igh voltage power MOSFET. It
provides 2.5A output with current mode control
for fast loop response and easy compensation.
The wide 4.5V t
o 20V i nput range
accommodates a variety of step-down
applications, including t hose in an automotive
input environment. A 100µA operational
quiescent current allows use in battery-powered
applications.
High power conversion efficiency over a wide
load range is a chieved by scalin g down the
switching fr equency at light load condition to
reduce the switching and gate driving losses.
The frequen cy foldback helps prevent inductor
current run away during startup and thermal
shutdown provides reliable, fa ult tolerant
operation.
By switching at 4MHz, the MP435 0 is able to
prevent switching relate d EMI (Elec tromagnetic
Interference) noise problems, such as tho se
found in AM radio and ADSL applications.
The MP4350 is available in a small 3mm x 3mm
10-pin QFN package.
2.5A, 4MHz, 20V
Converter
FEATURES
• 100 µA Quiescent Current
• Wide 4.5V to 20V Operating Input Range
• 150m Ω Internal Power MOSFET
• Up to 4MHz Programmable Switching
Frequency
• Ceramic Capacitor Stable
• Internal Soft-Start
• Internal Set Current Limit without a Current
Sensing Resistor
• Up to 95% Efficiency
• Output Adjustable from 0.8V to 16V
• Availablein a 10-Pin QNF (3mm x3mm) Packaeg
APPLICATIONS
• DSL Power
• Set Top Boxes
• Battery Powered Systems
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
C4
100nF
10
VIN
8,9 VIN
BST
SW 1,2
D1
EN
3 EN
FB 5
MP4350
7 FREQ
COMP 4
GND
5
C3
220pF
C6
NS
VOUT
3.3V
Efficiency vs
Load Current
100
90
VIN=5V
80
VIN=12V
70
60
50
40
30
0
VOUT=3.3V
0.5 1.0 1.5 2.0 2.5
LOAD CURRENT (A)
MP4350 Rev. 1.0
5/26/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
1
http://www.Datasheet4U.com
1 page  
MP4350 – 2.5A, 4MHz, 20V STEP-DOWN CONVERTER
OPERATION
The MP4 350 is a variable frequency,
non-synchronous, st ep-down switching
regulator with an inte grated high -side high
voltage power MOSF ET. It provi des a single
highly efficient solutio n with current mod e
control for fast loop response and easy
compensation. It features a wide input voltage
range, internal soft-star t control an d precision
current limiting. Its
very lo w operational
quiescent current makes it suitable for battery
powered applications.
PWM Control
At moderate to high output current, the MP4350
operates in a fixed fr equency, peak current
control mode to regulate the output voltage. A
PWM cycle is initiated by the internal clock. The
power MOSFET is turned on and remains on
until its cur rent reaches the value set by the
COMP voltage. When th e power switch is o ff, it
remains off for at lea st 100ns befor e the next
cycle starts. If, in one PWM period, the current
in the pow er MOSF ET does not reach the
COMP set current value, the power MOSFET
remains on, saving a turn-off operation.
VIN VIN
EN
VOUT
FB
REFERENCE UVLO/
THERMAL
SHUTDOWN
1.5ms SS
SS
Gm Error Amp
--
SS
0V8 +
INTERNAL
REGULATORS
ISW --
+
5V +--
2.6V
SW
Level
Shift
COMP
OSCILLATOR
+
--
CLK
ISW
COMP
GND
FREQ
BST
SW
VOUT
Figure 1—Functional Block Diagram
MP4350 Rev. 1.0
5/26/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
5
5 Page 
MP4350 – 2.5A, 4MHz, 20V STEP-DOWN CONVERTER
In this case (as shown in Figure 2), a third pole
set by the compensation capacitor (C6) and the
compensation resistor (R3) is used to
compensate the effect of the ESR zero on the
loop gain. This pole is located at:
fP3
=
1
2π × C6 × R3
The goal of compensation design is to shape
the converter transfer function to get a desired
loop gain. The system crossover frequency
where the feedback loo p has the u nity gain is
important. Lower crossover frequencies re sult
in slower line and loa d transient responses,
while higher crossover frequencies could cause
system unstable. A goo d rule of thu mb is to set
the crosso ver frequency to approximately
one-tenth of the switching frequency. The Table
3 lists the typical va lues of co mpensation
components for some st andard output voltages
with variou s output capacitors an d inductors.
The values of the compensation components
have been optimize d for fa st transient
responses and good stability at given conditions.
Table 3—Compensation Values for Typical
Output Voltage/Capacitor Combinations
VOUT
(V)
L (µH)
C2 R3 C3
(µF) (kΩ) (pF)
C6
1.8 4.7
47 105 100 None
2.5 4.7 - 6.8 22 54.9 220 None
3.3 6.8 -10 22 58.1 220 None
5 15 - 22 22 100 150 None
12 22 - 33 22 147 150 None
To optimize the compensation com ponents for
conditions n ot liste d in Table 3, th e following
procedure can be used.
1. Choose the compensation resistor (R3) to set
the desired crossover frequency. Determine the
R3 value by the following equation:
R3
=
2π × C2 × fC
GEA × GCS
×
VOUT
VFB
Where fC is the desired crossover frequency.
2. Choose t he compensation capacitor (C3) to
achieve the desired phase margin. For
applications with typical inductor values, setting
the compensation zero, fZ1, below one forth of
the crossover frequency provides sufficient
phase margin. Determine the C3 value by the
following equation:
C3
>
4
2π × R3 ×
fC
3. Determine if the second compensation
capacitor ( C6) is required. It is required if the
ESR zero of the output capacitor is loca ted at
less than half of the switching frequency, or the
following relationship is valid:
1
2π × C2 × RESR
<
fS
2
If this is t he case, then add the second
compensation capacitor (C6) to set the pole fP3
at the location of the ESR zero. Determine the
C6 value by the equation:
C6
=
C2 × RESR
R3
High Frequency Operation
The switching frequency of MP4 350 can b e
programmed up to 4MHz by an external resistor.
Please pay attention t o the follo wing if the
switching frequency is above 2MHz.
The minimum on time of MP4350 is about 80ns
(typ). Pulse skipping o peration ca n be seen
more easily at higher switching fre quency due
to the minimum on time. Recommended
operating voltage is 12 V or below, and 24V or
below at 2 MHz. Refer to Figure 2 below for
detailed information.
MP4350 Rev. 1.0
5/26/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
11
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| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet MP4350.PDF ] | |
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