EC9301A datasheet(10/16 Pages) E-CMOS

10 / 16 page

E-CMOS Corp. (www.ecmos.com.tw)

Page 10 of 16

5J22N Rev. F001

3A 150KHz PWM Buck DC/DC Converter

EC9301A

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 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 EC9301A is available in two packages, a 5-pin

TO-220B/TO-220 and a 5-pin surface mount TO-263.

The TO-220B/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 EC9301A 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

EC9301A

(TO-220B/TO-220

package) operating

buck

switching regulator in an ambient temperature of 25℃

(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.

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

, only small 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 EC9301A (TO-263 package) junction temperature rise

above ambient temperature with a 3A 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 3A 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

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