Datasheet

LTM4620A
11
4620afb
For more information www.linear.com/LTM4620A
OPERATION
Power Module Description
The LTM4620A 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 0.6V
DC
to 5.3V
DC
over 4.5V to 16V input
voltages. The typical application schematic is shown in
Figure 26. See Note 8 in the Electrical Characteristics
section for output current guideline.
The LTM4620A 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 f
SET
pin. See the Applications Information section.
With current mode control and internal feedback loop
compensation, the LTM4620A module has sufficient
stability 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 ±10% window around the regulation 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 LTM4620A is internally compensated to be stable over
all operating conditions. Table 5 provides a guide line for
input and output capacitances for several operating condi
-
tions. LTpowerCAD™ is available for transient and stability
analysis. The V
FB
pin is used to program the output volt-
age with a single external resistor to ground. A differential
remote
sense amplifier is available for sensing 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 PHMODE 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 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 TEMP pin is provided to allow the internal device tem
-
perature to be monitored using an onboard diode connected
PNP transistor. This diode connected PNP transistor is
grounded in the module and can be used as a general
temperature monitor using a device that is designed to
monitor the single-ended connecton.