AP1501-12K5 ANACHIP [Anachip Corp], AP1501-12K5 Datasheet - Page 8

• Manufacturer Part Number: AP1501-12K5
• Description: 150Khz, 3A PWM Buck DC/DC Converter
• Manufacturer: ANACHIP [Anachip Corp]

150Khz, 3A PWM Buck DC/DC Converter
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.
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
40V) 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 AP1501 is available in two packages, a 5-pin
TO-220 and a 5-pin surface mount TO-263.
The TO-220 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 AP1501 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
AP1501 (TO-220 package) operating as a buck
switching regulator in an ambient temperature of
25
Anachip Corp.
www.anachip.com.tw
ON /OFF
o
IN
C (still air). These temperature rise numbers are
Function Description
IN
– V
SAT
) and approximately – 0.5V,
OUT
/ V
IN
. To
8/12
all approximate and there are many factors that can
affect
temperatures require more heat sinking.
The TO-263 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
and ideally should have 2 or more square inches of
2 oz. Additional copper area improves the thermal
characteristics, but with copper areas greater than
approximately 6 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
2A 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.
higher than 2A 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.
AP1501
these
temperatures.
(TO-263
2
, only small improvements in
When load currents
package)
Higher
Rev.1.2 Aug. 23, 2005
AP1501
ambient
junction
2
,