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PDF MP4470A Data sheet ( Hoja de datos )
| Número de pieza | MP4470A | |
| Descripción | High-Efficiency Fast-Transient 5A 36V Synchronous Step-Down Converter | |
| Fabricantes | MPS | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MP4470A (archivo pdf) en la parte inferior de esta página. Total 18 Páginas | ||
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The Future of Analog IC Technology
MP4470/4470A
High-Efficiency, Fast-Transient, 5A, 36V
Synchronous, Step-Down Converter
DESCRIPTION
The MP447 0/4470A is a fully-integ rated, high-
frequency, synchronous, rectified, step-down,
switch-mode converter. It offers a very compact
solution t o achieve a 5A, continuous-outpu t
current ove r a wide i nput-supply range wit h
excellent load and line regulation. It also
provides fast transient response and good
stability for wide input-supply and l oad range.
The MP4470/4470A operates at h igh efficiency
over a wide output current load range.
MP4470 has full prote ction featur es include
SCP, OCP, OVP latch, UVP, a nd thermal
shutdown. MP4470A h as the same protection
features to MP4470 except has no OVP latch
function.
The MP44 70/4470A r equires a m inimal number
of rea dily-available, standard, exte rnal
components, and is ava ilable in a space-saving
3mm×4mm, 20-pin, QFN package.
FEATURES
• Wide 4.5V-to-36V Operating Input Range
• Guaranteed 5A, Continuous Output Current
• Internal 40mΩ High-Side, 20mΩ Low-Side
Power MOSFETs
• Proprietary Switching-Loss-Reduction
Technology
• 1% Reference Voltage
• Programmable Soft-Start Time
• Low Drop-out Mode
• 200kHz-to-1MHz Switching Frequency
• SCP, OCP, OVP Latch(MP4470 only), UVP,
and Thermal Shutdown
• Output Adjustable from 0.8V to 0.9×VIN
• Available in a 3×4mm 20-pin QFN Package
APPLICATIONS
• Notebook Systems and I/O Power
• Automotive Systems
• Networking Systems
• Industrial Supplies
• Optical Communications Systems
• Distributed Power and POL 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 An alog IC Technology” a re Re gistered T rademarks of Mo nolithic
Power Systems, Inc.
TYPICAL APPLICATION
100
90
80
70
60
50
40
30
20
10
0
0.01
0.1 1
OUTPUT CURRENT (A)
10
MP4470/4470A Rev. 1.1
www.MonolithicPower.com
8/26/2013
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
1
http://www.Datasheet4U.com
1 page  
MP4470/4470A–HIGH-EFFICIENCY, FAST-TRANSIENT, SYNCHRONOUS, STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
VIN = 24V, VOUT = 3.3V, L = 10µH, TA = +25°C, unless otherwise noted.
VO(AC)
10mV/div.
SW
10V/div.
IL
500mA/div.
VO(AC)
10mV/div.
SW
20V/div.
IL
1A/div.
VIN
10V/div.
VO
2V/div.
IL
200mA/div.
SW
10V/div.
VIN
10V/div.
VO
2V/div.
IL
2A/div.
SW
10V/div.
VIN
10V/div.
VO
2V/div.
IL
2A/div.
SW
20V/div.
VIN
10V/div.
VO
2V/div.
IL
5A/div.
SW
20V/div.
EN
2V/div.
VO
2V/div.
IL
500mA/div.
SW
20V/div.
EN
2V/div.
VO
2V/div.
IL
5A/div.
SW
20V/div.
EN
2V/div.
VO
2V/div.
IL
2A/div.
SW
20V/div.
MP4470/4470A Rev. 1.1
www.MonolithicPower.com
8/26/2013
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
5
5 Page 
MP4470/4470A–HIGH-EFFICIENCY, FAST-TRANSIENT, SYNCHRONOUS, STEP-DOWN CONVERTER
Figure 7 shows an equivalent circuit in PWM
mode with the HS-F ET OFF a nd without an
external ramp circuit. The ESR ripple dominates
the output ripple. The VFB downward slope is:
VSLOPE1
=
−E× SR
L
VREF
(7)
From equat ion 7, the V FB downward slope is
proportional to ESR/L. Therefore, it ’s necessary
to know the minimum ESR value of the outp ut
capacitors without an external ramp. There is
also an ind uctance limit: A smaller inductance
leads to more stability. Based on bench
experiments, keep V SLOPE1 around 15V/ms to
30V/ms.
In skip mode, the external ramp does not affect
the downward slope, an d V FB ripple’s downward
slope is the same with or without the extern al
ramp. Figure 8 shows an equivalent circuit wit h
the HS-FET off and the current modulator
regulating the LS-FET.
IMOD
Figure 8: Simplified Circuit in Skip Mode
The VFB ripple’s downward slope is:
()VSLOPE2 =
−VREF
R1R2+
× COUT
(8)
To keep the system s table during light loads,
avoid large V FB resistor s. Also, kee p the V SLOPE2
value around 0.4V/ms to 0.8mV/ ms. Note that
IMOD is excluded from the equation because it
does not impact the system’s light-load stability.
Soft-Start
The MP447 0/4470A employs soft start (SS) to
ensure a smooth outp ut during power-up. When
the EN pin goes HIGH, an internal current source
(8.5μA) charges up the SS capacit or (C SS). Th e
CSS voltage takes over the REF voltage to th e
PWM co mparator. The output voltage smoothl y
ramps up with V SS. Once V SS reach es the same
level as V REF, it continu es ramping up while V REF
takes over the PWM comparator. At this point,
soft-start f inishes and the MP4470/4470A enters
steady-state.
CSS is then:
CSS ()nF
=
tSS
(ms) ×μISS (
VREF ( V )
A)
(9)
If the out put capacitors have large capacitance
values, avoid setting a short SS or ri sk hitting the
current limit during SS. Select a minimum value
of 4.7nF if t he output capacitance value exceeds
330μF.
Power Good (PGOOD)
The MP4470/4470A ha s power-good (PGOOD)
output. The PGOOD pin is the op en drain of a
MOSFET. It should connect to VCC or some other
voltage source through a resistor (e .g. 100kΩ). In
the presence of an inp ut voltage, t he MOSFET
turns ON s o that the PGOOD pin is pulled to
GND before SS is ready. After V
FB reach es
90%×VREF, the PGOOD pin is pulled HIGH after a
delay; typically 700μs.
When the FB voltage drops to 85%×V REF, t he
PGOOD pin is pulled LOW.
Over-Current Protection (OCP) and Sho
Circuit Protection (SCP)
rt-
The MP4470/4470A has cycle-b y-cycle ove r-
current limit control. The induct or current is
monitored during the ON state. Once the inductor
current exceeds the current limit, the HS-FET
turns OFF. At the same time, th e OCP ti mer
starts. The OCP timer is set at 100μs. Hitting t he
current limit during each cycle during this 100 μs
time frame will trigger hiccup SCP.
If a short circuit occur s, the MP447 0/4470A will
immediately hit its current limit and VFB will dro p
below 50%×VREF (0.815V). The device consider s
this an outp ut dead sho rt and will tr igger hiccup
SCP immediately.
Over/Under-Voltage Protection (OVP/UVP)
The MP4470 monitors the output vo ltage through
the tap of a resistor divider to the FB pin to detect
output over-voltage conditions.
A V FB that
exceeds 125%×VREF (0.815V) triggers OVP latch-
off. Once OVP triggers, the LS-FET turns on t o
MP4470/4470A Rev. 1.1
www.MonolithicPower.com
8/26/2013
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet MP4470A.PDF ] | |
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