APE1705 Datasheet, PDF (7/12 Pages) Advanced Power Electronics Corp. – 150KHz, 3A PWM Buck DC/DC Converter

Advanced Power
Electronics Corp.
150KHz, 3A PWM Buck DC/DC Converter
APE1705
™ Function Descriptions
Pin Functions
Vcc
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.
Vss
Circuit ground.
SW
Internal switch. The voltage at this pin switches between (+V_CC – V_SAT) and
approximately – 0.5V, with a duty cycle of approximately V_OUT / V_CC. 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.
EN
Allows the switching regulator circuit to be shutdown using logic level signals thus
dropping the total input supply current to approximately 100uA. 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 Vcc) shuts the regulator down. If this shutdown
feature is not needed, the EN pin can be wired to the ground pin.
Thermal Considerations
The TO-263-5L 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 APE1705 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 APE1705 (TO263-5L package)
operating as a buck-switching regulator in an ambient temperature of 25Ċ (still air).
These temperature increments are all approximate and are affected by many factors.
Higher ambient temperatures requires more heat sinker.
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