Datasheet

LTM4649
9
4649f
For more information www.linear.com/LTM4649
OPERATION
Power Module Description
The LTM4649 is a high performance single output stand-
alone nonisolated switching mode DC/DC power supply.
It can provide up to 10A output current with few exter-
nal input and output capacitors. This module provides
precisely regulated output voltage programmable via
an external resistor from 0.6VDC to 3.3VDC over a 4.5V
to 16V input range. The typical application schematic is
shown in Figure 17.
The LTM4649 has an integrated constant-frequency cur-
rent mode regulator, power MOSFETs, inductor, and other
supporting discrete components. The typical switching
frequency is 450kHz. For switching noise-sensitive ap-
plications, it can be externally synchronized from 400kHz
to 750kHz. See the Applications Information section.
With current mode control and internal feedback loop
compensation, the LTM4649 module has sufficient stabil-
ity margins and good transient performance with a wide
range of output capacitors, especially with all ceramic
output capacitors.
Current mode control provides cycle-by-cycle fast current
limit in an overcurrent condition. An internal overvoltage
monitor protects the output voltage in the event of an
overvoltage >10%. The top MOSFET is turned off and the
bottom MOSFET is turned on until the output is cleared.
Pulling the RUN pin below 1.1V forces the regulator into a
shutdown state. The TRACK/SS pin is used for program-
ming the output voltage ramp and voltage tracking during
start-up. See the Application Information section.
The LTM4649 is internally compensated to be stable over
all operating conditions. Table 3 provides a guideline for
input and output capacitances for several operating con-
ditions. The Linear Technology µModule Power Design
Tool will be provided for transient and stability analysis.
The V
FB
pin is used to program the output voltage with a
single external resistor to ground.
A remote sense amplifier is provided in the LTM4649 for
accurately sensing output voltages ≤3.3V at the load point.
Multiphase operation can be easily employed with the
synchronization inputs using an external clock source.
See application examples.
High efficiency at light loads can be accomplished with
selectable Burst Mode operation 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.
A diode connected PNP transistor with base and collector
grounded is included in the module as a general purpose
single-ended temperature monitor. The temperature
monitor is intended to be used as a general temperature
monitor, see Applications Information section
The switching node pins are available for functional opera-
tion monitoring and a resistor-capacitor snubber circuit
can be careful placed on the switching node pin to ground
to dampen any high frequency ringing on the transition
edges. See the Applications Information section for details.