FAC1509PR datasheet(11/13 Pages) FS

11 / 13 page

Function Description

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

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 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

50uA. 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

32V) 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 FAC1509 is available in SOP8/DIP8 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

FAC1509 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 FAC1509 (SOP8/DIP8

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.

2008. 1. 28

11/13

FAC1509

Revision No : 0

2A 150KHZ PWM Buck DC/DC Converter

FAC1509PR Datasheet(PDF) 11 Page - First Silicon Co., Ltd

FAC1509PR Datasheet(HTML) 11 Page - First Silicon Co., Ltd

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13

Datasheet Download

Link URL