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MP1474 Schematic ( PDF Datasheet ) - MPS

Teilenummer MP1474
Beschreibung High-Efficiency 2A 16V 500kHz Synchronous Step-Down Converter
Hersteller MPS
Logo MPS Logo 




Gesamt 16 Seiten
MP1474 Datasheet, Funktion
MP1474
The Future of Analog IC Technology
DESCRIPTION
The MP1474 is a high-f requency, synchronous,
rectified, st ep-down, switch-mode converter
with built-in power MOSFETs. It o ffers a very
compact solution to achieve a 2A continuous
output curr ent with e xcellent loa d and line
regulation o ver a wide input supply range. The
MP1474 ha s synchronous mode operation fo r
higher efficiency over t he output current load
range.
Current-mode operation provides fast transien t
response and eases loop stabilization.
Full protection feature s include over-current
protection and thermal shut down.
The MP147 4 requires a minimal number of
readily-available standard external components,
and is available in a space- saving 8-pin
TSOT23 package.
High-Efficiency, 2A, 16V, 500kHz
Synchronous, Step-Down Converter
FEATURES
Wide 4.5V-to-16V Operating Input Range
100m /40mLow RDS(ON) Internal Power
MOSFETs
High-Efficiency Synchronous Mode
Operation
Fixed 500kHz Switching Frequency
Synchronizes from a 200kHz-to-2MHz
External Clock
Power-Save Mode at Light Load
Internal Soft-Start
Power Good Indicator
OCP Protection and Hiccup
Thermal Shutdown
Output Adjustable from 0.8V
Available in an 8-pin TSOT-23 Package
APPLICATIONS
Notebook Systems and I/O Power
Digital Set-Top Boxes
Flat-Panel Television and Monitors
Distributed Power Systems
All MPS parts are lead-free and adhere to the RoHS directive. For MPS green
status, please visit MPS website under Quality Assurance. “MPS” and “The
Future of Analog IC Technology” are Registered Trademarks of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
4.5V-16V
VIN
C1
22
EN/
SYNC
C5 R5
0.1 100k
2 IN
5
R3
20
BST
MP1474
6 EN/SYNC
SW 3
C4
L1
7 VCC
1 PG
GND
4
FB 8
R6
16k
3.3V/2A
C2
47 R1
40.2k
R2
13k
Efficiency vs.
Output Current
100VOUT=3.3V, IOUT=0.01A-2A
95
90 VIN=5V
85 VIN=12V
80
75 VIN=16V
70
65
60
55
50
0.0 0.4 0.8 1.2 1.6
OUTPUT CURRENT (A)
2.0
MP1474 Rev. 1.0
9/26/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
1
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MP1474 Datasheet, Funktion
MP1474 – SYNCHRONOUS STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Performance waveforms are tested on the evaluation board of the Design Example section.
VIN = 12V, VOUT = 3.3V, L=5.5μH, TA = 25°C, unless otherwise noted.
Startup through Enable
IOUT=2A
Shutdown through
Enable
IOUT=0A
Shutdown through
Enable
IOUT=2A
VOUT
2V/div.
VPG
5V/div.
VEN
5V/div.
VSW
10V/div.
IINDUCTOR
2A/div.
VOUT
2V/div.
VPG
5V/div.
VEN
5V/div.
VSW
10V/div.
IINDUCTOR
2A/div.
VOUT
2V/div.
VPG
5V/div.
VEN
5V/div.
VSW
10V/div.
IINDUCTOR
2A/div.
Startup through Input
Voltage
IOUT=0A
Startup through Input
Voltage
IOUT=2A
Shutdown through
Input Voltage
IOUT=0A
VOUT
2V/div.
VPG
5V/div.
VIN
5V/div.
VSW
5V/div.
IINDUCTOR
2A/div.
VOUT
2V/div.
VPG
5V/div.
VIN
5V/div.
VSW
5V/div.
IINDUCTOR
2A/div.
VOUT
2V/div.
VPG
5V/div.
VIN
5V/div.
VSW
5V/div.
IINDUCTOR
2A/div.
Shutdown through
Input Voltage
IOUT=2A
VOUT
2V/div.
VPG
5V/div.
VIN
5V/div.
VSW
5V/div.
IINDUCTOR
2A/div.
Input / Output Ripple
IOUT=2A
Load Transient Reponse
IOUT=1A-2A
VOUT/AC
20mV/div.
VIN/AC
200mV/div.
VSW
10V/div.
IL
2A/div.
VOUT/AC
50mV/div.
IOUT
1A/div.
MP1474 Rev. 1.0
9/26/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
6

6 Page









MP1474 pdf, datenblatt
MP1474 – SYNCHRONOUS STEP-DOWN CONVERTER
Selecting the Output Capacitor
The output capacitor (C2) maintains the DC
output voltage. Use ceramic, tantalum, or low-
ESR electrolytic capacitors. For best results,
use low ESR capacitors to keep the output
voltage ripple low. The output voltage ripple can
be estimated as:
VO1UT
VOUT
fSL 1



VOUT
VIN
RESR

8
1
fS C2
Where L 1 is the inducto r value and RESR is the
equivalent series resista nce (ESR) value of the
output capacitor.
For ceramic capa citors, the capacitance
dominates the impedance at the switching
frequency, and the ca pacitance causes the
majority of the outp ut voltage ripple. F or
simplification, the outp ut voltage ripple can be
estimated as:
ΔVO1UT
8fS
VOUT
2 L1
C2



VOUT
VIN
For tantalum or electrolytic capacit ors, the ESR
dominates the impedance at the switching
frequency. For simplification, the output ripple
can be approximated as:
ΔVOUT fSVLOUT1
1
VOUT
VIN
RESR
The charact eristics of th e output capacitor also
affect the stability of the regulation system. The
MP1474 ca n be optimized for a wide range of
capacitance and ESR values.
External Bootstrap Diode
An external bootstrap diode can enhance th e
efficiency of the regulat or given th e following
conditions:
VOUT is 5V or 3.3V; and
Duty cycle is high: D= VOUT >65%
VIN
In these cases, add an external BST diode from
the VCC pin to BST pin, as shown in Figure 6.
BST
MP1474
External BST Diode
IN4148
VCC
CBST
SW
L COUT
Figure 6: Optional External Bootstrap Diode to
Enhance Efficiency
The recommended external BST diode
is
IN4148, and the BST capacitor value is 0.1µF
to 1μF.
MP1474 Rev. 1.0
9/26/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
12

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