LTM4604 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTM4604' PDF : 20 Pages View PDF
LTM4604
OPERATION
Power Module Description
The LTM4604 is a standalone non-isolated switch mode
DC/DC power supply. It can deliver up to 4A of DC output
current with few external input and output capacitors.
This module provides a precise regulated output voltage
programmable via one external resistor from 0.8V DC to
5.0V DC over a 2.375V to 5.5V input voltage. A typical
application schematic is shown in Figure 15.
The LTM4604 has an integrated constant frequency cur-
rent mode regulator with built-in power MOSFETs with
fast switching speed. The typical switching frequency is
1.25MHz. With current mode control and internal feedback
loop compensation, the LTM4604 module has sufļ¬cient
stability margins and good transient performance under a
wide range of operating conditions and with a wide range
of output capacitors, even all ceramic output capacitors.
Current mode control provides cycle-by-cycle fast current
limit. In addition, foldback current limiting is provided
in an overcurrent condition while VOUT drops. Internal
overvoltage and undervoltage comparators pull the open-
drain PGOOD output low if the output feedback voltage exits
a Ā±7.5% window around the regulation point. Furthermore,
in an overvoltage condition, internal top FET M1 is turned
off and bottom FET M2 is turned on and held on until the
overvoltage condition clears.
Pulling the RUN pin below 0.5V forces the controller into its
shutdown state, turning off both M1 and M2. At low load
current, the module works in continuous current mode by
default to achieve minimum output voltage ripple.
The TRACK pin is used for power supply tracking. See the
Applications Information section.
The LTM4604 is internally compensated to be stable over
a wide operating range. Table 4 provides a guideline for
input and output capacitance for several operating condi-
tions. An excel loop analysis tool is provided for transient
and stability analysis.
The FB pin is used to program the output voltage with a
single resistor connected to ground.
4604f
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