LTM4628V(RevC) Просмотр технического описания (PDF) - Linear Technology
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LTM4628V Datasheet PDF : 36 Pages
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LTM4628
Operation
Power Module Description
The LTM4628 is a dual-output standalone nonisolated
switching mode DC/DC power supply. It can provide two
8A outputs with few external input and output capacitors
and setup components. This module provides precisely
regulated output voltages programmable via external
resistors from 0.6VDC to 5VDC over 4.5V to 26.5V input
voltages. The typical application schematic is shown in
Figure 28.
The LTM4628 has dual integrated constant-frequency cur-
rent mode regulators and built-in power MOSFET devices
with fast switching speed. The typical switching frequency
is 550kHz. For switching-noise sensitive applications, it
can be externally synchronized from 400kHz to 780kHz.
A resistor can be used to program a free run frequency
on the fSET pin. See the Applications Information section.
With current mode control and internal feedback loop
compensation, the LTM4628 module has sufficient stabil-
ity margins and good transient performance with a wide
range of output capacitors, even with all ceramic output
capacitors.
Current mode control provides cycle-by-cycle fast current
limit and foldback current limit in an overcurrent condition.
Internal overvoltage and undervoltage comparators pull
the open-drain PGOOD outputs low if the output feedback
voltage exits a ±7.5% window around the regulation point.
If the output voltage exceeds 10% above its normal op-
erating point then the bottom power MOSFET will try to
clamp the output to protect it.
Pulling the RUN pins below 1.1V forces the regulators into
a shutdown state, by turning off both MOSFETs. The TRACK
pins are used for programming the output voltage ramp and
voltage tracking during start-up or used for soft-starting
the regulator. See the Applications Information section.
The LTM4628 is internally compensated to be stable over
all operating conditions. Table 2 provides a guideline
for input and output capacitances for several operating
conditions. LTpowerCAD™ is available for transient and
stability analysis. The VFB pin is used to program the
output voltage with a single external resistor to ground.
A differential remote sense amplifier is available for sens-
ing the output voltage accurately on one of the outputs at
the load point, or in parallel operation sensing the output
voltage at the load point.
Multiphase operation can be easily employed with the
MODE_PLLIN, PHASMD, and CLKOUT pins. Up to 12
phases can be cascaded to run simultaneously with re-
spect to each other by programming the PHASMD pin to
different levels. See the Applications Information section.
High efficiency at light loads can be accomplished with
selectable Burst Mode operation or pulse-skipping
operation using the MODE_PLLIN pin. These light load
features will accommodate battery operation. Efficiency
graphs are provided for light load operation in the Typical
Performance Characteristics section. See the Applications
Information section for details.
A temperature diode is included inside the module to moni-
tor the temperature of the module. See the Applications
Information section for details.
The switch pins are available for functional operation
monitoring and a resistor-capacitor snubber circuit can
be carefully placed on the switch pin to ground to dampen
any high frequency ringing on the transition edges. See
the Applications Information section for details.
4628fc
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