TD1507 Techcode, TD1507 Datasheet - Page 9

• Manufacturer Part Number: TD1507
• Description: 2.5A 150KHZ PWM Buck DC/DC Converter
• Manufacturer: Techcode

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Function Description
Pin Functions
+V
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
Ground
Circuit ground.
Output
Internal switch. The voltage at this pin switches
between (+V
with a duty cycle of approximately V
minimize coupling to sensitive circuitry, the PC
board copper area connected to this pin should
be kept a minimum.
Feedback
Senses the regulated output voltage to complete
the feedback loop.
ON/OFF
Allows the switching regulator circuit to be
shutdown using logic level signals thus dropping
the total input supply current to approximately
80uA. 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
25V) shuts the regulator down. If this shutdown
feature is not needed, the ON /OFF pin can be
wired to the ground pin or it can be left open, in
either case the regulator will be in the ON
condition.
Thermal Considerations
The TD1507 is available in TO252-5L package.
The TO252 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 TD1507 junction temperature rises above
ambient temperature for a 2.5A load and different
input and output voltages. The data for these
curves was taken with the TD1507 (TO252
October, 20, 2005.
2.5A 150KHZ PWM Buck DC/DC Converter
IN
IN
– V
SAT
) and approximately – 0.5V,
OUT
/ V
IN
. To
9
package) operating as a buck switching regulator
in an ambient temperature of 25
These
approximate and there are many factors that can
affect
temperatures require more heat sinking.
The TO252 surface mount package tab is
designed to be soldered to the copper on a
printed circuit board. The copper and the board
are the heat sink for this package and the other
heat producing components, such as the catch
diode and inductor. The PC board copper area
that the package is soldered to should be at least
0.4 in
inches of 2 oz. Additional copper area improves
the thermal characteristics, but with copper areas
greater than approximately 6 in
improvements in heat dissipation are realized. If
further thermal improvements are needed, double
sided, multilayer PC board with large copper
areas and/or airflow are recommended.
The
temperature rise above ambient temperature with
a 2.5A load for various input and output voltages.
This data was taken with the circuit operating as a
buck switching regulator with all components
mounted on a PC board to simulate the junction
temperature under actual operating conditions.
This curve can be used for a quick check for the
approximate junction temperature for various
conditions, but be aware that there are many
factors that can affect the junction temperature.
When load currents higher than 2.5A are used,
double sided or multilayer PC boards with large
copper areas and/or airflow might be needed,
especially for high ambient temperatures and
high output voltages.
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.
2
, and ideally should have 2 or more square
TD1507
these
temperature
temperatures.
(TO252
Techcode Semiconductor Limited
rise
package)
numbers
Higher
Datasheet
2
TD1507
, only small
o
C (still air).
are
ambient
junction
all