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SS8014-xxG

Pin Description

PIN

NAME

FUNCTION

1

IN

Regulator Input. Supply voltage can range from +2.5V to +5.5V. Bypass with 1µF to GND.

2

GND

Ground. This pin also functions as a heatsink. Solder to large pads or the circuit board ground plane

to maximize thermal dissipation.

3

SHDN

Active-High Enable Input. A logic low reduces the supply current to less than 1µA. Connect to IN for

normal operation.

4

BYP

This is a reference bypass pin. It should connect external 10nF capacitor to GND to reduce output

≥ 1nF)

5

OUT

Regulator Output. Sources up to 150mA. Bypass with a 1µF, < 0.2

Ω typical ESR capacitor to GND.

Detailed Description

The block diagram of the SS8014-xx is shown in Figure 1.

It consists of an error amplifier, 1.25V bandgap reference,

PMOS output transistor, internal feedback voltage divider,

shutdown logic, over current protection circuit, and over

temperature protection circuit.

The internal feedback voltage divider’s central tap is

connected to the non-inverting input of the error amplifier.

The error amplifier compares non-inverting input with the

1.25V bandgap reference. If the feedback voltage is

higher than 1.25V, the error amplifier’s output becomes

higher so that the PMOS output transistor has a smaller

carrying capability of the PMOS output transistor, as a

result the output voltage decreases until the feedback

voltage is equal to 1.25V. Similarly, when the feedback

voltage is less than 1.25V, the error amplifier causes the

output PMOS to conduct more current to pull the feed-

back voltage up to 1.25V. Thus, through this feedback

action, the error amplifier, output PMOS, and the volt-

age-divider effectively form a unity-gain amplifier with the

feedback voltage forced to be the same as the 1.25V

given by the following equation:

(1)

Alternatively, the relationship between R1 and R2 is given

by:

(2)

Figure 1. Functional Diagram

SHDN

IN

OUT

SHUTDOWN

LOGIC

1.25V

Vref

¡Ð

ERROR

AMP

¡Ï

OVER CURRENT

PROTECT & DYNAMIC

FEEDBACK

GND

R1

R2

OVER TEMP.

PROTECT

BYP

C

BYP

SHDN

IN

OUT

SHUTDOWN

LOGIC

1.25V

Vref

¡Ð

ERROR

AMP

¡Ï

OVER CURRENT

PROTECT & DYNAMIC

FEEDBACK

GND

R1

R2

OVER TEMP.

PROTECT

BYP

C

BYP

1/12/2005 Rev.2.10