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PDF LTM4628 Data sheet ( Hoja de datos )
| Número de pieza | LTM4628 | |
| Descripción | Dual 8A or Single 16A DC/DC uModule Regulator | |
| Fabricantes | Linear | |
| Logotipo |  |
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LTM4628
Dual 8A or Single 16A
DC/DC µModule Regulator
FEATURES
n Complete Standalone Dual Power Supply
n Single 16A or Dual 8A Output
n Wide Input Voltage Range: 4.5V to 26.5V
n Output Voltage Range: 0.6V to 5.5V
n ±1.5% Total DC Output Error
n Differential Remote Sense Amplifier
n Current Mode Control/Fast Transient Response
n Adjustable Switching Frequency
n Overcurrent Foldback Protection
n Multiphase Parallel Current Sharing with
Multiple LTM4628s
n Frequency Synchronization
n Internal Temperature Sensing Diode Output
n Selectable Burst Mode® Operation
n Soft-Start/Voltage Tracking
n Output Overvoltage Protection
n Low Profile (15mm × 15mm × 4.32mm) LGA Package
APPLICATIONS
n Telecom and Networking Equipment
n Storage and ATCA Cards
n Industrial Equipment
L, LT, LTC, LTM, Linear Technology, the Linear logo, µModule, Burst Mode and PolyPhase
are registered and LTpowerCAD is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
DESCRIPTION
The LTM®4628 is a complete dual 8A output switching
mode DC/DC power supply and can be easily configured
to provide a single 2-phase 16A output. Included in the
package are the switching controller, power FETs, inductor,
and all supporting components. Operating from an input
voltage range of 4.5V to 26.5V, the LTM4628 supports two
outputs each with an output voltage range of 0.6V to 5.5V,
set by a single external resistor. Its high efficiency design
delivers 8A continuous current for each output. Only a
few input and output capacitors are needed.
The device supports frequency synchronization, multi-
phase operation, Burst Mode operation and output voltage
tracking for supply rail sequencing. It has an onboard
temperature diode for device temperature monitoring.
High switching frequency and a current mode architec-
ture enable a very fast transient response to line and load
changes without sacrificing stability.
Fault protection features include overvoltage and
overcurrentwww.DataSheet.net/ protection. The power module is offered in
a space saving and thermally enhanced 15mm × 15mm
× 4.32mm LGA package. The LTM4628 is PB-free and
ROHS compliant.
TYPICAL APPLICATION
Dual 8A, 1.5V and 1.2V Output DC/DC µModule® Regulator
4.7µF
VIN
4.5V TO
26.5V *
10k
10µF
35V 120k
×4
*
5.1V ZENER
0.1µF
100k
* PULL-UP RESISTOR AND
ZENER ARE OPTIONAL.
MODE_PLLIN CLKOUT INTVCC
VIN
TEMP
RUN1
RUN2
TRACK1
TRACK2
LTM4628
fSET
PHASMD
SGND GND
DIFFP
EXTVCC PGOOD1
VOUT1
VOUTS1
DIFFOUT
SW1
VFB1
VFB2
COMP1
COMP2
VOUTS2
VOUT2
SW2
PGOOD2
DIFFN
100µF
6.3V
VOUT1
1.5V AT 8A
470µF
6.3V
60.4k
40.2k
100µF
6.3V
470µF
6.3V
VOUT2
1.2V AT 8A
4628 TA01a
Efficiency and Power Loss
at 12V Input
95 1.2V
90 1.5V
85
80
75
70
65
60
55
EFFICIENCY
POWER LOSS
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
50 0
012345678
LOAD CURRENT (A)
4628 TA01b
4628fb
1
Datasheet pdf - http://www.DataSheet4U.co.kr/
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTM4628
5VIN Efficiency
100 FREQ = 500kHz
95
90
85
80
75
3.3VOUT
2.5VOUT
70
1.5VOUT
1.2VOUT
65 0.8VOUT
012345678
OUTPUT CURRENT (A)
4628 G01
12VIN Efficiency
100 FREQ = 500kHz, 700kHz for 3.3V AND 5V
95
90
85
80
75
70
5VOUT
3.3VOUT
65
2.5VOUT
1.5VOUT
60 1.2VOUT
0.8VOUT
55
012345678
OUTPUT CURRENT (A)
4628 G02
24VIN Efficiency
95 FREQ = 500kHz, 700kHz for 3.3V AND 5V
90
85
80
75
70
65
60 5VOUT
55
3.3VOUT
2.5VOUT
50 1.5VOUT
012345678
OUTPUT CURRENT (A)
4628 G03
Burst Mode Pulse-Skipping
Efficiency
100
90
Burst Mode OPERATION
80
70
60
50
40
30
20 PULSE-SKIPPING MODE
10
0
0.001
0.01 0.1
1
OUTPUT CURRENT (A)
10
4628 G04
0.8V Load Transient
1.2V Load Transient
VOUT
50mV/DIV
www.DataSheet.net/
VOUT
50mV/DIV
IOUT
2A/DIV
IOUT
2A/DIV
100µs/DIV
4628 G05
12VIN, 0.8VOUT, 0A TO 4A LOAD STEP AT 4A/µs
COUT1 4× 100µF 6.3V X5R CERAMIC 1210 CASE SIZE
SWITCHING FREQUENCY 400kHz
CFF CAPACITOR = 47pF
100µs/DIV
4628 G06
12VIN, 1.2VOUT, 0A TO 4A LOAD STEP AT 4A/µs
COUT1, 4× 100µF 6.3V X5R CERAMIC 1210 CASE SIZE
SWITCHING FREQUENCY 500kHz
CFF CAPACITOR = 47pF
1.5V Load Transient
1.8V Load Transient
2.5V Load Transient
VOUT
50mV/DIV
VOUT
50mV/DIV
VOUT
100mV/DIV
IOUT
2A/DIV
IOUT
2A/DIV
IOUT
2A/DIV
100µs/DIV
4628 G07
12VIN, 1.5VOUT, 0A TO 4A LOAD STEP AT 4A/µs
COUT1 4× 100µF 6.3V X5R CERAMIC 1210 CASE SIZE
SWITCHING FREQUENCY 500kHz
CFF CAPACITOR = 47pF
100µs/DIV
4628 G08
12VIN, 1.8VOUT, 0A TO 4A LOAD STEP AT 4A/µs
COUT1 4× 100µF 6.3V X5R CERAMIC 1210 CASE SIZE
SWITCHING FREQUENCY 500kHz
CFF CAPACITOR = 47pF
100µs/DIV
4628 G09
12VIN, 2.5VOUT, 0A TO 4A LOAD STEP AT 4A/µs
COUT1, 4× 100µF 6.3V X5R CERAMIC 1210 CASE SIZE
SWITCHING FREQUENCY 500kHz
CFF CAPACITOR = 47pF
4628fb
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Datasheet pdf - http://www.DataSheet4U.co.kr/
5 Page 
LTM4628
APPLICATIONS INFORMATION
The typical LTM4628 application circuit is shown in
Figure 28. External component selection is primarily
determined by the maximum load current and output
voltage. Refer to Table 4 for specific external capacitor
requirements for particular applications.
VIN to VOUT Step-Down Ratios
There are restrictions in the maximum VIN and VOUT step-
down ratio that can be achieved for a given input voltage.
Each output of the LTM4628 is capable of 98% duty cycle,
but the VIN to VOUT minimum dropout is still shown as a
function of its load current and will limit output current
capability related to high duty cycle on the top side switch.
Minimum on-time tON(MIN) is another consideration in op-
erating at a specified duty cycle while operating at a certain
frequency due to the fact that tON(MIN) < D/fSW, where D
is duty cycle and fSW is the switching frequency. tON(MIN)
is specified in the electrical parameters as 90ns.
Output Voltage Programming
The PWM controller has an internal 0.6V reference voltage.
As shown in the Block Diagram, a 60.4kΩ internal feedback
resistor connects between the VOUTS1 to VFB1 and VOUTS2
to VFB2. It is very important that these pins be connected
to their respective outputs for proper feedback regulation.
Overvoltage can occur if these VOUTS1 and VOUTS2 pins are
left floating when used as individual regulators, or at least
one of them is used in paralleled regulators. The output
voltage will default to 0.6V with no feedback resistor on
either VFB1 or VFB2. Adding a resistor RFB from VFB pin to
GND programs the output voltage:
VOUT
=
0.6V
•
60.4k + RFB
RFB
Table 1. VFB Resistor Table vs Various Output Voltages
VOUT 0.6V 1.0V 1.2V 1.5V 1.8V 2.5V 3.3V
RFB Open 90.9k 60.4k 40.2k 30.2k 19.1k 13.3k
5.0V
8.25k
For parallel operation of multiple channels the same feed-
back setting resistor can be used for the parallel design.
This is done by connecting the VOUTS1 to the output as
shown in Figure 2, thus tying one of the internal 60.4k
resistors to the output. All of the VFB pins tie together with
one programming resistor as shown in Figure 2.
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 VOUTS 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. For example in Figure 2, the total Thevenin
equivalent resistance of the VFB pin is (60.4k // RFB), which
is 30.2k where RFB is equal to 60.4k for a 1.2V output.
Four phases connected in parallel equates to a worse case
feedback current of 4 • IFB equals 80nA maximum. The volt-
age error is 80nA • 30.2k = 2.4mV. If VOUTS2 is connected
as shown in Figure 2 to VOUT, and another 60.4k resistor
is connected from VFB2 to ground, then the voltage error
is reduced to 1.2mV. If the voltage error is acceptable then
no additional connections are necessary. The onboard
60.4k resistor is 0.5% accurate and the VFB resistor can
be chosen by the user to be as accurate as needed.
All COMP pins are tied together for current sharing be-
tween the phases. The TRACK pins can be tied together
and a single soft-start capacitor can be used to soft-start
the regulator. The soft-start equation will need to have the
soft-startwww.DataSheet.net/ current parameter increased by the number of
paralleled channels. See TRACK/Soft-Start Pin section.
0.1µF
COMP1 LTM4628
COMP2
VOUT1
VOUT2
TRACK1
TRACK2
60.4k
60.4k
VOUTS1
VOUTS2
VFB1
VFB2
COMP1 LTM4628
COMP2
60.4k
TRACK1
TRACK2
60.4k
VOUT1
VOUT2
VOUTS1
VOUTS2
VFB1
VFB2
4628 F02
4 PARALLELED OUTPUTS
FOR 1.2V AT 32A
OPTIONAL CONNECTION
OPTIONAL
RFB
60.4k
USED TO LOWER TOTAL
THEVENIN EQUIVALENT TO
LOWER IFB VOLTAGE ERROR
RFB
60.4k
Figure 2. 4-Phase Parallel Configurations
4628fb
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Datasheet pdf - http://www.DataSheet4U.co.kr/
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTM4628.PDF ] | |
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