LTM8047 LINER [Linear Technology], LTM8047 Datasheet - Page 10

• Manufacturer Part Number: LTM8047
• Description: 3.1VIN to 32VIN Isolated ?Module DC/DC Converter
• Manufacturer: LINER [Linear Technology]

LTM8048
OPERATION
The LTM8048 is a stand-alone isolated flyback switching
DC/DC power supply that can deliver up to 440mA of
output current. This module provides a regulated output
voltage programmable via one external resistor from 2.5V
to 13V. It is also equipped with a high performance linear
post regulator. The input voltage range of the LTM8048 is
3.1V to 32V. Given that the LTM8048 is a flyback converter,
the output current depends upon the input and output
voltages, so make sure that the input voltage is high
enough to support the desired output voltage and load
current. The Typical Performance Characteristics section
gives several graphs of the maximum load versus V
several output voltages.
A simplified block diagram is given. The LTM8048 contains
a current mode controller, power switching element, power
transformer, power Schottky diode, a modest amount of
input and output capacitance and a high performance
linear post regulator.
The LTM8048 has a galvanic primary to secondary isola-
tion rating of 725VDC. This is verified by applying 725VDC
between the primary to secondary for 1 second and then
applying –725VDC for 1 second. For details please refer
to the Isolation and Working Voltage section.
10
IN
for
An internal regulator provides power to the control cir-
cuitry. The bias regulator normally draws power from the
V
voltage higher than 3.1V, bias power will be drawn from
the external source, improving efficiency. V
exceed V
LTM8048, disconnecting the output and reducing the input
current to 1μA or less.
The LTM8048 is a variable frequency device. For a fixed
input and output voltage, the frequency increases as the
load increases. For light loads, the current through the
internal transformer may be discontinuous.
The post regulator is a high performance 300mA low
dropout regulator with micropower quiescent current and
shutdown. The device is capable of supplying 300mA at
a dropout voltage of 300mV. Output voltage noise can be
lowered to 20μV
with the addition of a 0.01μF reference bypass capacitor.
Additionally, this reference bypass capacitor will improve
transient response of the regulator, lowering the settling
time for transient load conditions. The linear regulator is
protected against both reverse input and reverse output
voltages.
IN
pin, but if the BIAS pin is connected to an external
IN
. The RUN pin is used to turn on or off the
RMS
over a 100Hz to 100kHz bandwidth
BIAS
must not
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