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PDF LTM4611 Data sheet ( Hoja de datos )
| Número de pieza | LTM4611 | |
| Descripción | 15A DC/DC uModule Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTM4611www.DataSheet4U.com
Ultralow VIN, 15A DC/DC
µModule Regulator
Features
n Complete Switch Mode Power Supply
n Input Voltage Range: 1.5V to 5.5V
n 15A DC Output
n Output Voltage Range: 0.8V to 5V
n ±1.5% Total DC Output Error
n Differential Remote Sensing for Precision
Regulation
n Current Mode Control/ Fast Transient Response
n Overcurrent Foldback Protection
n Parallel Multiple LTM®4611s for Current Sharing
n Frequency Synchronization
n Selectable Pulse-Skipping or Burst Mode® Operation
n Soft-Start/Voltage Tracking
n Up to 94% Efficiency
n Output Overvoltage Protection
n Small 15mm × 15mm × 4.32mm LGA Package
Applications
n Telecom Servers and Networking Equipment
n Storage and ATCA Cards
n General Purpose Point of Load Regulation
Description
The LTM4611 is a high density 15A output, switch mode
DC/DC buck converter power supply capable of operating
from very low voltage input supplies. Included in the pack-
age are the buck switching controller, power FETs, induc-
tor and loop-compensation components. The LTM4611
delivers up to 15A continuous current at high efficiency
from an input voltage of 1.5VIN up to 5.5VIN. The output
voltage is set between 0.8V and 5V by a resistor. Only a
few input and output capacitors are needed.
High switching frequency and a current mode architecture
enable a very fast transient response to line and load
changes without sacrificing stability. The device supports
frequency synchronization, multiphase/current sharing
operation, Burst Mode operation and output voltage
tracking for supply rail sequencing.
The LTM4611 is available in a thermally enhanced 15mm
× 15mm × 4.32mm LGA package. The LTM4611 is PB-free
and RoHS compliant.
L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode, PolyPhase and µModule are
registered trademarks of Linear Technology Corporation. All other trademarks are the property
of their respective owners. Protected by U.S. Patents, including 5481178, 5847554, 6580258,
6304066, 6476589, 6774611, 6677210.
Typical Application
1.5VIN to 5.5VIN, 15A Step-Down DC/DC µModule® Regulator
VIN
1.5V TO 5.5V
22µF
s3
CSS
0.1µF
VIN PGOOD
TRACK/SS
VOUT
LTM4611
VFB
RUN
VOUT_LCL
MODE_PLLIN
SGND
DIFFVOUT
VOSNS+
GND VOSNS–
VOUT**
STEP-DOWN
CFF* 15A
100µF*
s4
CP* RFB**
4611 TA01
*SEE TABLE 5
**SEE TABLE 1
Efficiency vs Load Current
96
94
92
90
88
86
84
82
80
78
0
5 10
LOAD CURRENT (A)
15
4611 TA01b
5VIN, 3.3VOUT
3.3VIN, 2.5VOUT
2.5VIN, 1.5VOUT
2.5VIN, 1.2VOUT
3.3VIN, 1VOUT
1.5VIN, 0.9VOUT
5VIN, 1VOUT
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LTM4611www.DataSheet4U.com
E lectrical Characteristics The l denotes the specifications which apply over the full internal operating
junction temperature range, otherwise specifications are at TA = 25°C, VIN = 3.3V, per the typical application in Figure 21.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
PLLFLTR/fSET(FLOAT) PLLFLTR/fSET Open-Circuit
Voltage
PLLFLTR/fSET Pin Voltage When Floating
1.23 V
Frequency Nominal Nominal Frequency
Frequency Low Lowest Frequency
Frequency High Highest Frequency
IPLLFLTR
PLLFLTR
Sourcing Capability
Sinking Capability
RMODE(PLLIN)
VIH
VIL
Mode_PLLIN
Clock
Mode_PLLIN Input Resistance
Clock Input Level High
Clock Input Level Low
Clock Input Duty Cycle Range
PLLFLTR/fSET Floating
PLLFLTR/fSET = 0.85V
PLLFLTR/fSET = 2.0V
Mode_PLLIN
Mode_PLLIN
Frequency
Frequency
>
<
ffOOSSCC
500
330
780
–13
13
250
2.0
40 50
0.6
60
kHz
kHz
kHz
µA
µA
kΩ
V
V
%
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTM4611 is tested under pulsed load conditions such that
TJ ≈ TA. The LTM4611E is guaranteed to meet performance specifications
over the 0°C to 125°C operating junction temperature (TJ) range.
Specifications over the full –40°C to 125°C operating junction temperature
range are assured by design, characterization and correlation with
statistical process controls. The LTM4611I is guaranteed to meet
specifications over the full –40°C to 125°C operating junction temperature
range. Note that the maximum ambient temperature consistent with
these specifications is determined by specific operating conditions in
conjunction with board layout, the rated package thermal resistance and
other environmental factors.
Note 3: Consistent with Pb-free 260°C peak IR reflow soldering profiles.
See Application Note 100.
Note 4: See output current derating curves for different VIN, VOUT and TA.
Note 5: The minimum on-time condition is specified for a peak-to-peak
inductor ripple current of ~40% of IMAX Load. (See the Typical Applications
section)
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LTM4611www.DataSheet4U.com
Applications Information
The typical LTM4611 application circuit is shown in
Figure 21. External component selection is primarily
determined by the maximum load current and output
voltage. Refer to Table 5 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 still a function of its load
current at very low input voltages. A dropout voltage of
300mV from input to output of LTM4611 is achievable
at 15A load, but reflected input voltage ripple and noise
should be taken into consideration in such applications.
Additionally, the transient-handling capability of the source
supply feeding LTM4611 can become an important factor
in truly achieving ultralow dropout at high output current.
For example, VIN can sag or overshoot dramatically when
LTM4611 responds to heavy transient step loads on its
output, if insufficient input bypass capacitance is used in
combination with a sluggish source supply.
When VOUT is expected to be within 600mV of VIN, or
when the caliber of the source supply is in question, it
is recommended to evaluate the amount and quality of
input bypass capacitance needed to maintain one’s target
dropout voltage with the source supply that will be used
in the end application. Demo Board DC1588A can be used
for such evaluation.
At very low duty cycles the minimum specified on-time
must be maintained. See the Frequency Adjustment sec-
tion and temperature derating curves.
To prevent overstress to the µpower bias generator, do
not ramp up VIN at a rate exceeding 5V/µs (in practice, it
is difficult to violate this guideline.) There is no restriction
on how rapidly VIN may be discharged.
Output Voltage Programming
The PWM controller has an internal 0.8V ±1.75% reference
voltage over temperature. As shown in the Block Diagram,
a 60.4k internal feedback resistor connects the VOUT_LCL
and VFB pins together. When the remote sense amplifier
is used, then DIFFVOUT 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 0.8V
with no feedback resistor. Adding a resistor RFB from VFB
to GND programs the output voltage:
VOUT
=
0.8V
•
60.4k +R
R FB
FB
Table 1. VFB Resistor Table vs Various Output Voltages
VOUT 0.8V 1.0V 1.2V 1.5V 1.8V 2.5V 3.3V
RFB (kΩ) Open 243 121 68.1 47.5 28.0 19.1
5.0V
11.5
For parallel operation of N LTM4611s, the following equa-
tion can be used to solve for RFB:
RFB
=
60.4k
VOUT
0.8V
/N
–1
Tie the VFB pins together for each parallel output. The
COMP, TRACK/SS, VOUT_LCL, and RUN pins must also be
tied together as shown in Figures 18 and 19.
For parallel applications, best noise immunity can be
achieved by placing capacitors of value CP from VFB to GND,
and value CFF from VOUT to VFB, local to each µModule.
If space limitations impede realizing this, then placement
of capacitors of value N • CP from VFB to GND, and value
N • CFF from VOUT to the bussed VFB signal, can suffice.
Input Capacitors
The LTM4611 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 ce-
ramics are a good choice with RMS ripple current ratings
of ~2A each. A 100µF to 150µF 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.
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11
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| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LTM4611.PDF ] | |
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