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PDF LTM4637 Data sheet ( Hoja de datos )
| Número de pieza | LTM4637 | |
| Descripción | 20A DC/DC uModule Step-Down Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LTM4637 (archivo pdf) en la parte inferior de esta página. Total 28 Páginas | ||
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FEATURES
n Complete 20A Switch Mode Power Supply
n 4.5V to 20V Input Voltage Range
n 0.6V to 5.5V Output Voltage Range
n ±1.5% Total DC Output Voltage Error
(–40°C to 125°C)
n Differential Remote Sense Amplifier for Precision
Regulation for (VOUT ≤ 3.3V)
n Current Mode Control/Fast Transient Response
n Parallel Current Sharing (Up to 80A)
n Frequency Synchronization
n Selectable Pulse-Skipping or Burst Mode® Operation
n Soft-Start/Voltage Tracking
n Up to 88% Efficiency (12VIN, 1.8VOUT)
n Overcurrent Foldback Protection
n Output Overvoltage Protection
n Internal Temperature Monitor
n Overtemperature Protection
n 15mm × 15mm × 4.32mm LGA Package
APPLICATIONS
n Telecom Servers and Networking Equipment
n Industrial Equipment
n Medical Systems
n High Ambient Temperature Systems
LTM4637
20A DC/DC µModule
Step-Down Regulator
DESCRIPTION
The LTM®4637 is a complete 20A output high efficiency
switch mode step-down DC/DC µModule (micromodule)
regulator. Included in the package are the switching control-
ler, power FETs, inductor and compensation components.
Operating over an input voltage range from 4.5V to 20V,
the LTM4637 supports an output voltage range of 0.6V
to 5.5V, set by a single external resistor. Only a few input
and output capacitors are needed.
Current mode operation allows precision current sharing
of up to four LTM4637 regulators to obtain up to 80A
output. 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, Burst Mode operation and output voltage tracking
for supply rail sequencing. A diode-connected PNP transis-
tor is available for use as an internal temperature monitor.
The LTM4637 is offered in a 15mm × 15mm × 4.32mmhttp://www.DataSheet4U.net/
LGA package. The LTM4637 is RoHS compliant. The
LTM4637 is pin compatible with the LTM4627, a 15A
DC/DC µModule regulator.
L, LT, LTC, LTM, PolyPhase, Burst Mode, µModule, Linear Technology, the Linear logo are
registered trademarks and LTpowerCAD is a trademark 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
12VIN, 1.2VOUT, 20A DC/DC µModule® Regulator
2.2µF
VIN
12V 22µF
16V 10k
×4
0.1µF
VIN
COMP
EXTVCC INTVCC PGOOD
VOUT
TRACK/SS
VOUT_LCL
RUN LTM4637
fSET
MODE_PLLIN
DIFF_OUT
VOSNS+
VOSNS–
330pF
100µF*+
6.3V
×2
VOUT
1.2V
20A
470µF
6.3V
×2
TEMP
* SEE TABLE 5
** SEE TABLE 1
SGND GND
VFB
RFB**
60.4k
4637 TA01a
For more information www.linear.com/LTM4637
12VIN Efficiency vs Load Current
100 1.2VOUT
95
250kHz
CCM
90
85
80
75
70
65
0 2 4 6 8 10 12 14 16 18 20
OUTPUT CURRENT (A)
4637 TA01b
4637f
1
datasheet pdf - http://www.DataSheet4U.net/
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTM4637
Efficiency vs Load Current
with 5VIN
100
95
90
85
80
1VOUT, 250kHz, CCM
75 1.2VOUT, 250kHz, CCM
1.5VOUT, 350kHz, CCM
70
1.8VOUT, 350kHz, CCM
2.5VOUT, 450kHz, CCM
65 3.3VOUT, 600kHz, CCM
0 2 4 6 8 10 12 14 16 18 20
OUTPUT CURRENT (A)
4637 G01
Burst Mode Efficiency
vs Load Current
95
90
85
80
75
70
65
0
5VIN, 1.8VOUT, 350kHz
8VIN, 1.8VOUT, 350kHz
12VIN, 1.8VOUT, 350kHz
0.5 1 1.5 2 2.5
OUTPUT CURRENT (A)
3
4637 G04
1.2V Transient Response
Efficiency vs Load Current with
8VIN (Limit 5V Output to 15A)
100
95
Efficiency vs Load Current with
12VIN (Limit 5V Output to 15A)
100
95
90 90
85
80 1VOUT, 250kHz, CCM
1.2VOUT, 250kHz, CCM
75 1.5VOUT, 350kHz, CCM
1.8VOUT, 350kHz, CCM
70
2.5VOUT, 450kHz, CCM
3.3VOUT, 600kHz, CCM
65 5VOUT, 600kHz, CCM
0 2 4 6 8 10 12 14 16 18 20
OUTPUT CURRENT (A)
4637 G02
Pulse-Skipping Mode Efficiency
vs Load Current
95
90
85
85
80 1VOUT, 250kHz, CCM
1.2VOUT, 250kHz, CCM
75 1.5VOUT, 350kHz, CCM
1.8VOUT, 350kHz, CCM
70
2.5VOUT, 450kHz, CCM
3.3VOUT, 600kHz, CCM
65 5VOUT, 600kHz, CCM
0 2 4 6 8 10 12 14 16 18 20
OUTPUT CURRENT (A)
4637 G03
1V Transient Response
OUTPUT
TRANSIENT
50mV/DIV
200µs/DIV
80
75
http://www.DataSheet4U.net/
70
65
60
0
5VIN, 1.8VOUT, 350k
8VIN, 1.8VOUT, 350k
12VIN, 1.8VOUT, 350k
0.5 1
1.5 2
2.5
OUTPUT CURRENT (A)
3
4637 G05
1.5V Transient Response
LOAD STEP
5A/DIV
VIN = 12V
200µs/DIV
VOUT = 1V
IOUT = 0A TO 10A, CFF = 330pF
OUTPUT CAPACITORS:
3 × 470µF POSCAP CAPACITORS
2 × 100µF CERAMIC CAPACITORS
1.8V Transient Response
4637 G06
OUTPUT
TRANSIENT
50mV/DIV
200µs/DIV
OUTPUT
TRANSIENT
50mV/DIV
200µs/DIV
OUTPUT
TRANSIENT
50mV/DIV
200µs/DIV
LOAD STEP
5A/DIV
LOAD STEP
5A/DIV
LOAD STEP
5A/DIV
VIN = 12V
200µs/DIV
VOUT = 1.2V
IOUT = 0A TO 10A, CFF = 330pF
OUTPUT CAPACITORS:
3 × 470µF POSCAP CAPACITORS
2 × 100µF CERAMIC CAPACITORS
4637 G07
VIN = 12V
200µs/DIV
VOUT = 1.5V
IOUT = 0A TO 10A, CFF = 330pF
OUTPUT CAPACITORS:
3 × 470µF POSCAP CAPACITORS
2 × 100µF CERAMIC CAPACITORS
4637 G08
VIN = 12V
200µs/DIV
VOUT = 1.8V
IOUT = 0A TO 10A, CFF = 330pF
OUTPUT CAPACITORS:
3 × 470µF POSCAP CAPACITORS
2 × 100µF CERAMIC CAPACITORS
4637 G09
For more information www.linear.com/LTM4637
4637f
5
datasheet pdf - http://www.DataSheet4U.net/
5 Page 
LTM4637
APPLICATIONS INFORMATION
to optimize the transient performance. Stability criteria cycles, thus skipping operation cycles. This mode has
are considered in the Table 5 matrix, and LTpowerCAD is lower ripple than Burst Mode operation and maintains a
available for stability analysis. Multiphase operation will higher frequency operation than Burst Mode operation.
reduce effective output ripple as a function of the number of
phases. Application Note 77 discusses this noise reduction Forced Continuous Operation
versus output ripple current cancellation, but the output
capacitance should be considered carefully as a function
of stability and transient response. LTpowerCAD can be
used to calculate the output ripple reduction as the number
of implemented phases increase by N times.
In applications where fixed frequency operation is more
critical than low current efficiency, and where the lowest
output ripple is desired, forced continuous operation
should be used. Forced continuous operation can be
enabled by tying the MODE_PLLIN pin to ground. In this
Burst Mode Operation
mode, inductor current is allowed to reverse during low
output loads, the COMP voltage is in control of the current
The LTM4637 is capable of Burst Mode operation in which comparator threshold throughout, and the top MOSFET
the power MOSFETs operate intermittently based on load always turns on with each oscillator pulse. During start-up,
demand, thus saving quiescent current. For applications forced continuous mode is disabled and inductor current
where maximizing the efficiency at very light loads is a is prevented from reversing until the LTM4637’s output
high priority, Burst Mode operation should be applied. To voltage is in regulation.
enable Burst Mode operation, simply float the MODE_PLLIN
pin. During Burst Mode operation, the peak current of the Multiphase Operation
inductor is set to approximately 30% of the maximum peak
current value in normal operation even though the voltage
at the COMP pin indicates a lower value. The voltage at the
COMP pin drops when the inductor’s average current is
greater than the load requirement. As the COMP voltage
drops below 0.5V, the burst comparator trips, causing
the internal sleep line to go high and turn off both power
MOSFETs.
For outputs that demand more than 20A of load current,
multiple LTM4637 devices can be paralleled to provide
morehttp://www.DataSheet4U.net/ output current without increasing input and output
ripple voltage. The MODE_PLLIN pin allows the LTM4637
to be synchronized to an external clock and the internal
phase-locked loop allows the LTM4637 to lock onto input
clock phase as well. The fSET resistor is selected for nor-
mal frequency, then the incoming clock can synchronize
In sleep mode, the internal circuitry is partially turned the device over the specified range. See Figure 24 for a
off, reducing the quiescent current. The load current is synchronizing example circuit.
now being supplied from the output capacitors. When the
output voltage drops, causing COMP to rise, the internal
sleep line goes low, and the LTM4637 resumes normal
operation. The next oscillator cycle will turn on the top
power MOSFET and the switching cycle repeats.
A multiphase power supply significantly reduces the
amount of ripple current in both the input and output ca-
pacitors. The RMS input ripple current is reduced by, and
the effective ripple frequency is multiplied by, the number
of phases used (assuming that the input voltage is greater
Pulse-Skipping Mode Operation
than the number of phases used times the output voltage).
The output ripple amplitude is also reduced by the number
In applications where low output ripple and high efficiency of phases used. See Application Note 77.
at intermediate currents are desired, pulse-skipping
mode should be used. Pulse-skipping operation allows
the LTM4637 to skip cycles at low output loads, thus
increasing efficiency by reducing switching loss. Tying
the MODE_PLLIN pin to INTVCC enables pulse-skipping
operation. With pulse-skipping mode at light load, the
The LTM4637 device is an inherently current mode con-
trolled device, so parallel modules will have good current
sharing. This will balance the thermals in the design. Tie
the COMP and VFB pins of each LTM4637 together to
share the current evenly. Figure 24 shows a schematic of
internal current comparator may remain tripped for several the parallel design.
4637f
For more information www.linear.com/LTM4637
11
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11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LTM4637.PDF ] | |
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