LT1083CK View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LT1083CK

7.5A, 5A, 3A Low Dropout Positive Adjustable Regulators

Linear Technology 

BLOCK DIAGRA

LT1083/LT1084/LT1085 Fixed

VIN

THERMAL

LIMIT

VOUT

GND

LT1083/4/5 BD

APPLICATIO S I FOR ATIO

The LT1083 family of three-terminal regulators are easy to

use and have all the protection features that are expected

in high performance voltage regulators. They are short

circuit protected, have safe area protection as well as

thermal shutdown to turn off the regulator should the

temperature exceed about 165°C.

These regulators offer lower dropout voltage and more

precise reference tolerance. Further, the reference stabil-

ity with temperature is improved over older types of

regulators. The only circuit difference between using the

LT1083 family and older regulators is that they require an

output capacitor for stability.

Stability

The circuit design used in the LT1083 family requires the

use of an output capacitor as part of the device frequency

compensation. For all operating conditions, the addition of

150μF aluminum electrolytic or a 22μF solid tantalum on

the output will ensure stability. Normally capacitors much

smaller than this can be used with the LT1083. Many

different types of capacitors with widely varying charac-

teristics are available. These capacitors differ in capacitor

tolerance (sometimes ranging up to ±100%), equivalent

series resistance, and capacitance temperature coeffi-

cient. The 150μF or 22μF values given will ensure stability.

Normally, capacitor values on the order of 100μF are used

in the output of many regulators to ensure good transient

response with heavy load current changes. Output capaci-

tance can be increased without limit and larger values of

output capacitance further improve stability and transient

response of the LT1083 regulators.

Another possible stability problem that can occur in

monolithic IC regulators is current limit oscillations.

These can occur because in current limit the safe area

protection exhibits a negative impedance. The safe area

protection decreases the current limit as the input-to-

output voltage increases.That is the equivalent of having

a negitive resistance since increasing voltage causes

current to decrease. Negitive resistance during current

limit is not unique to the LT1083 series and has been

present on all power IC regulators. The value of negative

resistance is a function of how fast the current limit is

1083ffd

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