Analog Microelectronics, Inc.
AME1084
5A Low Dropout
Positive Voltage Regulator
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 V
OUT
to GND t o
provide compensation feedback to the internal gain
stage. This is to ensure stability at the output termi-
nal. Typically, a 10µF tantalum or 50µF aluminum
electrolytic is sufficient.
Note: It is important that the ESR for this capacitor
does not exceed 0.5Ω.
The output capacitor dose not have a theoretical
upper limit and increasing its value will increase
stability. C
OUT
= 100µF 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.
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 V
REF
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:
R2
) + I
ADJ
x R2
V
OUT
= V
REF
( 1 +
R1
On fixed versions of AME1084, the voltage di-
vider is provided internally.
V
IN
C
1
IN
ADJ
I
AD J
50µA
OUT
V
REF
R1
V
OUT
R2
V
O U T
= V
R E F
(1+ R 2 ) + I
A D J
x R2
R1
Figure 3
R
P
Parasitic
Line Resistance
V
IN
IN
ADJ
OUT
2. Thermal protection
AME1084 has thermal protection which limits
junction temperature to 150
O
C. However, de-
vice functionality is only guaranteed to a maxi-
mum junction temperature of +125
O
C.
The power dissipation and junction tempera-
ture for AME1084 in TO-220 package are given
by
P
D
= (V
IN
- V
OUT
) x I
OUT
T
JUNCTION
= T
AMBIENT
+ ( P
D
x
θ
JA
)
Note: T
JUNCTION
must not exceed 125
O
C
R1
(Connect R1 to case)
R
L
R2
Connect
R2 to load
Figure 4
6
AME [ ANALOG MICROELECTRONICS ]
