LT1585-1.5 데이터 시트보기 (PDF) - Linear Technology

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LT1585-1.5

Fixed 1.5V, 4.6A and 5A Low Dropout, Fast Response GTL+ Regulators

Linear Technology 

LT1585-1.5/LT1585A-1.5

W

W

SI PLIFIED SCHE ATIC

VIN

THERMAL

LIMIT

GND

VOUT

1585-1.5 SS

APPLICATIONS INFORMATION

General

The LT1585-1.5/LT1585A-1.5 3-terminal regulators are

easy to use and have all the protection features expected

in high performance linear regulators. The devices are

short-circuit protected, safe-area protected and provide

thermal shutdown to turn off the regulators if the junction

temperature exceeds about 150°C.

The ICs are pin compatible with the LT1083/LT1084/LT1085

family of linear regulators but offer lower dropout voltage

and faster transient response. The trade-off for this im-

proved performance is a 7V maximum supply voltage.

Similar to the LT1083/LT1084/LT1085 family, the LT1585-

1.5/LT1585A-1.5 regulators require an output capacitor for

stability. However, the improved frequency compensation

permits the use of capacitors with much lower ESR while still

maintaining stability. This is critical in addressing the needs

of modern low voltage, high speed microprocessors.

Current generation microprocessors and their associated

circuitry cycle load current from almost zero to several

amps in tens of nanoseconds. Output voltage tolerances

are tighter and include transient response as part of the

specification. The LT1585-1.5/LT1585A-1.5 are specifi-

cally designed to meet the fast current load step require-

ments of these applications and save total cost by needing

less output capacitance in order to maintain regulation.

Stability

The circuit design in the LT1585-1.5/LT1585A-1.5 re-

quires the use of an output capacitor as part of the

frequency compensation. For all operating conditions, the

addition of a 22µF solid tantalum or a 100µF aluminum

electrolytic on the output ensures stability. Normally, the

LT1585-1.5/LT1585A-1.5 can use smaller value capaci-

tors. Many different types of capacitors are available and

have widely varying characteristics. These capacitors differ

in capacitor tolerance (sometimes ranging up to ±100%),

equivalent series resistance, equivalent series inductance

and capacitance temperature coefficient. The LT1585-1.5/

LT1585A-1.5 frequency compensation optimizes frequency

response with low ESR capacitors. In general, use capaci-

tors with an ESR of less than 1Ω.

Normally, capacitor values on the order of several hundred

microfarads are used on the output of the regulators to

ensure good transient response with heavy load current

changes. Output capacitance can increase without limit

and larger values of output capacitance further improve the

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