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PDF LTM4649 Data sheet ( Hoja de datos )
| Número de pieza | LTM4649 | |
| Descripción | 10A Step-Down DC/DC uModule Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTM4649
10A Step-Down DC/DC
µModule Regulator
Features
n 10A DC Output Current
n Input Voltage Range: 4.5V to 16V
n Output Voltage Range: 0.6V Up to 3.3V
n No Heat Sink or Current Derating Up to 85°C
Ambient Temperature
n ±1.5% Total DC Voltage Output Error
n Multiphase Operation with Current Sharing
n Remote Sense Amplifier
n Built-In General Use Temperature Monitor
n Selectable Pulse-Skipping Mode/Burst Mode®
Operation for High Efficiency at Light Load
n Soft-Start/Voltage Tracking
n Protection: Output Overvoltage and Overcurrent
Foldback
n 9mm × 15mm × 4.92mm BGA Package
Applications
n Telecom, Networking and Industrial Equipment
n Point of Load Regulation
L, LT, LTC, LTM, Burst Mode, µModule, PolyPhase, Linear Technology and the Linear logo are
registered trademarks of Linear Technology Corporation. All other trademarks are the property
of their respective owners. Protected by U.S. Patents, including 5481178, 5705919, 5929620,
6100678, 6144194, 6177787, 6304066 and 6580258. Other patents pending.
Description
The LTM®4649 is a complete 10A high efficiency switching
mode step-down DC/DC µModule® regulator in a 9mm ×
15mm × 4.92 BGA package. Included in the package are
the switching controller, power FETs, inductor, and all sup-
port components. Operating over an input voltage range
of 4.5V to 16V, the LTM4649 supports an output voltage
range of 0.6V to 3.3V, set by a single external resistor. This
high efficiency design delivers 10A continuous current.
Only bulk input and output capacitors are needed.
High switching frequency and a current mode architecture
enables a very fast transient response to line and load
changes without sacrificing stability. The device supports
frequency synchronization, programmable multiphase
operation, spread spectrum, output voltage tracking for
supply rail sequencing.
Fault protection features include overvoltage protection,
overcurrent protection. The LTM4649 is offered in a small
thermally enhanced 9mm × 15mm × 4.92mm BGA pack-
age. The LTM4649 is available with SnPb (BGA) or RoHS
compliant terminal finish.
Typical Application
4.5V to 16V Input, 1.5V Output DC/DC
µModule Regulator
VIN
4.5V TO 16V
22µF
16V
×2
CLKIN
VIN
INTVCC
SW
FREQ
VOUT
VOUT_LCL
DIFFOUT
RUN LTM4649 DIFFP
MODE
DIFFN
PHMODE
TRACK/SS
VFB
COMP
TEMP
0.1µF GND
PGOOD
CLKOUT
100µF
6.3V
×2
VOUT
1.5V
10A
6.65k
4649 TA01a
Efficiency and Power Loss
at 12V and 5V Input
95 3.0
90 2.5
85 2.0
80 1.5
75 1.0
70
65
0
VIN = 12V 0.5
VIN = 5V
0
2 4 6 8 10
LOAD CURRENT (A)
4649 TA01b
Current Derating: 12V Input,
1.5VOUT, No Heat Sink
12
10
8
6
4
2
400LFM
200LFM
0LFM
0
0 20 40 60 80 100 120
AMBIENT TEMPERATURE (°C)
4649 TA01c
For more information www.linear.com/LTM4649
4649fa
1
1 page  
Typical Performance Characteristics
LTM4649
12VIN Efficiency
100
95
90
85
80
75
VOUT = 1V, 450kHz
VOUT = 1.2V, 450kHz
70
VOUT = 1.5V, 450kHz
VOUT = 2.5V, 750kHz
65 VOUT = 3.3V, 750kHz
0 2 4 6 8 10
LOAD CURRENT (A)
4649 G01
5VIN, 1VOUT Load Transient
5VIN Efficiency
100
95
90
85
80
75
VOUT = 1V, 450kHz
VOUT = 1.2V, 450kHz
70
VOUT = 1.5V, 450kHz
VOUT = 2.5V, 450kHz
VOUT = 3.3V, 450kHz
65
0 2 4 6 8 10
LOAD CURRENT (A)
4649 G02
12VIN, 1VOUT Load Transient
CCM, Burst Mode and Pulse-
Skipping Mode Efficiency
100
90
VIN = 12V
VOUT = 1.5V
80
70
60
50
40
30
20
10
0
0.01
CCM
PULSE-
SKIPPPING
Burst Mode
OPERATION
0.1 1
LOAD CURRENT (A)
10
4649 G03
5VIN, 1.5VOUT Load Transient
IOUT
5A/DIV
AC
VOUT
100mV/DIV
AC
IOUT
5A/DIV
AC
VOUT
100mV/DIV
AC
IOUT
5A/DIV
AC
VOUT
100mV/DIV
AC
50µs/DIV
4649 G04
5VIN, 1VOUT, 5A TO 10A LOAD STEP
COUT = 2 • 220µF 4V CERAMIC CAPACITOR
NO CFF CAPACITOR
12VIN, 1.5VOUT Load Transient
50µs/DIV
4649 G05
12VIN, 1VOUT, 5A TO 10A LOAD STEP
COUT = 2 • 220µF 4V CERAMIC CAPACITOR
NO CFF CAPACITOR
5VIN, 2.5VOUT Load Transient
50µs/DIV
4649 G06
5VIN, 1.5VOUT, 5A TO 10A LOAD STEP
COUT = 2 • 220µF 4V CERAMIC CAPACITOR
NO CFF CAPACITOR
12VIN, 2.5VOUT Load Transient
IOUT
5A/DIV
AC
VOUT
100mV/DIV
AC
IOUT
5A/DIV
AC
VOUT
100mV/DIV
AC
IOUT
5A/DIV
AC
VOUT
100mV/DIV
AC
50µs/DIV
4649 G07
12VIN, 1.5VOUT, 5A TO 10A LOAD STEP
COUT = 2 • 220µF 4V CERAMIC CAPACITOR
NO CFF CAPACITOR
50µs/DIV
4649 G08
5VIN, 2.5VOUT, 5A TO 10A LOAD STEP
COUT = 2 • 220µF 4V CERAMIC CAPACITOR
NO CFF CAPACITOR
50µs/DIV
4649 G09
12VIN, 2.5VOUT, 5A TO 10A LOAD STEP, 750kHz
COUT = 2 • 220µF 4V CERAMIC CAPACITOR
NO CFF CAPACITOR
For more information www.linear.com/LTM4649
4649fa
5
5 Page 
LTM4649
Applications Information
The typical LTM4649 application circuit is shown in Fig-
ure 17. External component selection is primarily deter-
mined by the maximum load current and output voltage.
Refer to Table 3 for specific external capacitor requirements
for particular applications.
VIN to VOUT Step-Down Ratios
There are restrictions in the VIN to VOUT step-down ratio
that can be achieved for a given input voltage. The VIN to
VOUT minimum dropout is a function of load current and
at very low input voltage and high duty cycle applications
output power may be limited as the internal top power
MOSFET is not rated for 10A operation at higher ambient
temperatures. At very low duty cycles the minimum 110ns
on-time must be maintained. See the Frequency Adjust-
ment section and temperature derating curves.
Output Voltage Programming
The PWM controller has an internal 0.6V ±0.5% refer-
ence voltage. As shown in the Block Diagram, a 10k
0.5% internal feedback resistor connects the VOUT_LCL
and VFB pins together. When the remote sense amplifier
is used, then DIFFOUT is connected to the VOUT_LCL pin.
If the remote sense amplifier is not used, then VOUT_LCL
connects to VOUT. The output voltage will default to 0.6V
with no feedback resistor. Adding a resistor RFB from VFB
to ground programs the output voltage:
VOUT
=
0.6V
•
10k + RFB
RFB
Table 1. VFB Resistor Table vs Various Output Voltages
VOUT(V) 0.6 1.0 1.2 1.5 1.8 2.5
RFB(k)
OPEN 15
10 6.65 4.99 3.09
3.3
2.21
For parallel operation of N LTM4649, the following equa-
tion can be used to solve for RFB:
10k
RFB
=
N
VOUT
0.6
–1
In parallel operation the VFB pins have an IFB current of
20nA maximum each channel. To reduce output voltage
error due to this current, an additional VOUT_LCL pin can
be tied to VOUT, and an additional RFB resistor can be used
to lower the total Thevenin equivalent resistance seen by
this current.
Input Capacitors
The LTM4649 module should be connected to a low AC
impedance DC source. Additional input capacitors are
needed for the RMS input ripple current rating. The ICIN(RMS)
equation which follows can be used to calculate the input
capacitor requirement. Typically 22µF X7R ceramics are a
good choice with RMS ripple current ratings of ~2A each.
A 47µF to 100µF surface mount aluminum electrolytic bulk
capacitor can be used for more input bulk capacitance.
This bulk input capacitor is only needed if the input source
impedance is compromised by long inductive leads, traces
or not enough source capacitance. If low impedance power
planes are used, then this bulk capacitor is not needed.
For a buck converter, the switching duty cycle can be
estimated as:
D
=
VOUT
VIN
Without considering the inductor ripple current, for each
output, the RMS current of the input capacitor can be
estimated as:
ICIN(RMS)
=
IOUT(MAX )
η%
•
D • (1− D)
In the previous equation, η% is the estimated efficiency of
the power module. The bulk capacitor can be a switcher-rat-
ed electrolytic aluminum capacitor or a Polymer capacitor.
Output Capacitors
The LTM4649 is designed for low output voltage ripple
noise. The bulk output capacitors defined as COUT are
chosen with low enough effective series resistance (ESR)
to meet the output voltage ripple and transient require-
ments. COUT can be a low ESR tantalum capacitor, low ESR
Polymer capacitor or ceramic capacitors. The typical output
capacitance range is from 200µF to 470µF. Additional output
filtering may be required by the system designer if further
reduction of output ripple or dynamic transient spikes is
For more information www.linear.com/LTM4649
4649fa
11
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| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTM4649.PDF ] | |
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