AME1084ACCS datasheet(6/16 Pages) AME

6 / 16 page

Analog Microelectronics, Inc.

AME1084

5A Low Dropout

Positive Voltage Regulator

n Application Description

1. Output voltage adjustment

Like most regulators, the AME1084 regulates

the output by comparing the output voltage to

an internally generated reference voltage. On

the adjustable version, the VREF is available ex-

ternally as 1.25V between V

OUT and ADJ.

The

voltage ratio formed by R1 and R2 should be

set to conduct 10mA (minimum output load).

The output voltage is given by the following

equation:

OUT = VREF ( 1 +

) + I

ADJ x R2

On fixed versions of AME1084, the voltage di-

vider is provided internally.

Figure 3

3. Current limit protection

AME1084 is protected against overload conditions.

Current protection is triggered at typical 7.5A.

4. Stability and load regulation

AME1084 requires a capacitor from VOUT to GND t o

provide compensation feedback to the internal gain

stage. This is to ensure stability at the output termi-

nal. Typically, a 10

µF tantalum or 50µF aluminum

electrolytic is sufficient.

Note: It is important that the ESR for this capacitor

does not exceed 0.5

Ω.

The output capacitor dose not have a theoretical

upper limit and increasing its value will increase

stability. COUT = 100

µF or more is typical for high cur-

rent regulator design.

For the adjustable version, the best load regulation is

accomplished when the top of theresistor

divider

(R1) is connected directly to theoutput pin of the

AME1084. When so connected, R

P is not multiplied

by the divider ratio.

For fixed output versions, the top of R1 is internally

connected to the output. The ground pin can be con-

nected to low side of the load to eliminate ground loop

errors.

2. Thermal protection

AME1084 has thermal protection which limits

junction temperature to 150OC. However, de-

vice functionality is only guaranteed to a maxi-

mum junction temperature of +125OC.

The power dissipation and junction tempera-

ture for AME1084 in TO-220 package are given

D = (VIN - VOUT) x IOUT

JUNCTION = TAMBIENT + ( PD x θJA)

Note: T

JUNCTION must not exceed 125

Figure 4

OUT = VREF (1+

) + I

ADJ x R2

OUT

ADJ

REF

AD J

µA

OUT

ADJ

Parasitic

Line Resistance

Connect

R2 to load

(Connect R1 to case)

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