LTM4623 Ver la hoja de datos (PDF) - Linear Technology
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LTM4623 Datasheet PDF : 26 Pages
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LTM4623
Operation
The LTM4623 is a standalone nonisolated switch mode DC/
DC power supply. It can deliver up to 3A DC output current
with few external input and output capacitors. This module
provides precisely regulated output voltage adjustable
between 0.6V to 5.5V via one external resistor over a 4V
to 20V input voltage range. With an external bias supply
above 4V connected to SVIN, this module operates with
an input voltage down to 2.375V. The typical application
schematic is shown in Figure 24.
The LTM4623 contains an integrated constant on-time
valley current mode regulator, power MOSFETs, inductor,
and other supporting discrete components. The default
switching frequency is 1MHz. For output voltages between
3.3V and 5.5V, an external 162k resistor is required between
FREQ and SGND pins to set the operating frequency to
2MHz to optimize inductor current ripple. For switching
noise-sensitive applications, the switching frequency can
be adjusted by external resistors and the μModule regulator
can be externally synchronized to a clock within ±30% of
the set frequency. See the Applications Information section.
With current mode control and internal feedback loop
compensation, the LTM4623 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 cur-
rent limiting. Foldback current limiting is provided in an
overcurrent condition indicated by a drop in VFB reducing
inductor valley current to approximately 40% of the origi-
nal value. Internal output overvoltage and undervoltage
comparators pull the open-drain PGOOD output low if the
output feedback voltage exits a ±10% window around the
regulation point. Continuous operation is forced during OV
and UV condition except during start-up when the TRACK
pin is ramping up to 0.6V.
Furthermore, in order to protect the internal power MOSFET
devices against transient voltage spikes, the LTM4623
constantly monitors the VIN pin for an overvoltage condi-
tion. When VIN rises above 23.5V, the regulator suspends
operation by shutting off both power MOSFETs. Once VIN
drops below 21.5V, the regulator immediately resumes
normal operation. The regulator does not execute its
soft-start function when exiting an overvoltage condition.
Multiphase operation can be easily employed with the
synchronization and phase mode controls. Up to 12 phases
can be cascaded to run simultaneously with respect to
each other by programming the PHMODE pin to different
levels. The LTM4623 has CLKIN and CLKOUT pins for
PolyPhase operation of multiple devices or frequency
synchronization.
Pulling the RUN pin below 1.1V forces the controller into
its shutdown state, turning off both power MOSFETs
and most of the internal control circuitry. At light load
currents, discontinuous mode (DCM) operation can be
enabled to achieve higher efficiency compared to continu-
ous mode (CCM) by pulling the MODE pin to SGND. The
TRACK/SS pin is used for power supply tracking and
soft-start programming. See the Applications Informa-
tion section.
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For more information www.linear.com/LTM4623
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