LTM4620 Ver la hoja de datos (PDF) - Analog Devices
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LTM4620 Datasheet PDF : 40 Pages
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LTM4620
OPERATION
Power Module Description
The LTM4620 is a dual-output standalone nonisolated
switching mode DC/DC power supply. It can provide two
13A 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 2.5VDC over 4.5V to 16V input
voltages. The typical application schematic is shown in
Figure 23. See Note 8 in the Electrical Characteristics sec-
tion for output current guideline.
The LTM4620 has dual integrated constant-frequency cur-
rent mode regulators and built-in power MOSFET devices
with fast switching speed. The typical switching frequency
is 500kHz. 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 LTM4620 module has sufficient sta-
bility 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 condi-
tion. Internal overvoltage and undervoltage comparators
pull the open-drain PGOOD outputs low if the output
feedback voltage exits a ±10% window around the regu-
lation point. As the output voltage exceeds 10% above
regulation, the bottom MOSFET will turn on to clamp the
output voltage. The top MOSFET will be turned off. This
overvoltage protect is feedback voltage referred.
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 LTM4620 is internally compensated to be stable over
all operating conditions. Table 4 provides a guide line for
input and output capacitances for several operating con-
ditions. The LTpowerCAD® will be provided 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
respect 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 opera-
tion using the MODE_PLLIN pin. These light load fea-
tures 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 mon-
itor the temperature of the module. See the Applications
Information section for details.
A TEMP pin is provided to allow the internal device tem-
perature to be monitored using an onboard diode con-
nected PNP transistor. This diode connected PNP transis-
tor is grounded in the module and can be used as a gen-
eral temperature monitor using a device that is designed
to monitor the single-ended connection.
For more information www.linear.com/LTM4620
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