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TD1583 View Datasheet(PDF) - Unspecified

Part NameDescriptionManufacturer
TD1583 3A 380KHz 28V PWM Buck DC/DC Converter ETC
Unspecified 
TD1583 Datasheet PDF : 16 Pages
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Techcode®
3A 380KHz 28V PWM Buck DC/DC Converter
Function Description
DATASHEET
TD1583
Pin Functions
VIN
This is the positive input supply for the IC switching
regulator. A suitable input bypass capacitor must be
present at this pin to minimize voltage transients and to
supply the switching currents needed by the regulator
Gnd
Circuit ground.
SW
Internal switch. The voltage at this pin switches between
(VIN – VSAT) and approximately – 0.5V, with a duty cycle
of approximately VOUT / VIN. To minimize coupling to
sensitive circuitry, the PC board copper area connected
to this pin should be kept a minimum.
FB
Senses the regulated output voltage to complete the
feedback loop.
EN
Allows the switching regulator circuit to be shutdown
using logic level signals thus dropping the total input
supply current to approximately 30uA. Pulling this pin
below a threshold voltage of approximately 0.7 V turns
the regulator down, and pulling this pin above 1.3V (up
to a maximum of 12V) shuts the regulator on. For
automatic starup condition , can be implemented by the
addition of a resistive voltage divider from VIN to GND.
Thermal Considerations
The TD1583 is available in SOP8 package.
The SOP8 package needs a heat sink under most
conditions. The size of the heat sink depends on the
input voltage, the output voltage, the load current and the
ambient temperature. The TD1583 junction temperature
rises above ambient temperature for a 3A load and
different input and output voltages. The data for these
curves was taken with the TD1583 (SOP8 package)
operating as a buck-switching regulator in an ambient
temperature of 25oC (still air). These temperature rise
numbers are all approximate and there are many factors
that can affect these temperatures. Higher ambient
temperatures require more heat sinking.
For the best thermal performance, wide copper traces
and generous amounts of printed circuit board copper
should be used in the board layout. (Once exception to
this is the output (switch) pin, which should not have
large areas of copper.) Large areas of copper provide the
best transfer of heat (lower thermal resistance) to the
surrounding air, and moving air lowers the thermal
resistance even further.
Package thermal resistance and junction temperature
rise numbers are all approximate, and there are many
factors that will affect these numbers. Some of these
factors include board size, shape, thickness, position,
location, and even board temperature. Other factors are,
trace width, total printed circuit copper area, copper
thickness, single or double-sided, multi-layer board and
the amount of solder on the board.
The effectiveness of the PC board to dissipate heat also
depends on the size, quantity and spacing of other
components on the board, as well as whether the
surrounding air is still or moving. Furthermore, some of
these components such as the catch diode will add heat
to the PC board and the heat can vary as the input
voltage changes. For the inductor, depending on the
physical size, type of core material and the DC
resistance, it could either act as a heat sink taking heat
away from the board, or it could add heat to the board.
Setting the Output Voltage
The output voltage is set using a resistive
voltage divider from the output voltage to FB. The
voltage divider divides the
December, 23, 2009.
Techcode Semiconductor Limited
11
www.techcodesemi.com
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