AP1519 Ver la hoja de datos (PDF) - Anachip Corporation
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AP1519 Datasheet PDF : 9 Pages
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300KHz, 2A PWM Buck DC/DC Converter
AP1519
Function Description
Pin Functions
+VIN
This is the positive input supply for the IC switching
regulator. A suitable input bypass capacitor must be
presented at this pin to minimize voltage transients
and to supply the switching currents needed by the
regulator.
Ground
Circuit ground.
Output
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
minimized.
Feedback
Senses the regulated output voltage to complete
the feedback loop.
SD
Allows the switching regulator circuit to be
shutdown using logic level signals thus dropping
the total input supply current to approximately
150uA. Pulling this pin below a threshold voltage of
approximately 1.3V turns the regulator on, and
pulling this pin above 1.3V (up to a maximum of
18V) shuts the regulator down. If this shutdown
feature is not needed, the SD pin can be wired to
the ground pin.
Thermal Considerations
The SOP-8 package needs a heat sink under most
conditions. The size of the heatsink depends on the
input voltage, the output voltage, the load current
and the ambient temperature. The AP1519 junction
temperature rises above ambient temperature for a
2A load and different input and output voltages.
The data for these curves was taken with the
AP1519 (SOP-8 package) operating as a
buck-switching regulator in an ambient temperature
of 25oC (still air). These temperature increments
are all approximate and are affected by man factors.
Higher ambient temperatures requires more heat
sinker.
For the best thermal performance, wide copper
traces and generous amounts of printed circuit
board copper should be used in the board layout.
(One exception 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 increments are all approximate. The
increments are affected by a lot of factors. 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.
Anachip Corp.
www.anachip.com.tw
Rev.1.0 Oct 5, 2004
8/9
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