AME, Inc.
5A Low Dropout
Positive Voltage Regulator
AME1084
n Application Description
1. Output Voltage Adjustment
3. Current Limit Protection
Like most regulators, the AME1084 regulates the out-
put by comparing the output voltage to an internally gen-
erated reference voltage. On the adjustable version, the
VREF is available externally as 1.25V between VOUT 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:
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
to GND to
OUT
provide compensation feedback to the internal gain stage.
This is to ensure stability at the output terminal. Typi-
cally, a 10mF tantalum or 50mF aluminum electrolytic is
sufficient.
R2
VOUT = VREF ( 1 +
) + IADJ x R2
R1
On fixed versions of AME1084, the voltage divider is
provided internally.
(Note: It is important that the ESR for this capacitor does not ex-
ceed 0.5W.)
VIN
VOUT
The output capacitor does not have a theoretical upper
limit and increasing its value will increase stability. COUT
= 100mF or more is typical for high current regulator de-
sign.
IN
OUT
ADJ
VREF
R1
C1
For the adjustable version, the best load regulation is
accomplished when the top of the resistor divider (R1) is
connected directly to the output pin of the AME1084.
IADJ
50mA
R2
When so connected, R is not multiplied by the divider
P
ratio.
For fixed output versions, the top of R1 is internally
connected to the output. The ground pin can be connected
to low side of the load to eliminate ground loop errors.
R2
R1
) + IADJ x R2
VOUT = VREF (1+
2. Thermal Protection
AME1084 has thermal protection which limits junction
temperature to 150oC. However, device functionality is
only guaranteed to a maximum junction temperature of
+125oC.
RP
Parasitic
Line Resistance
VIN
IN
OUT
ADJ
The power dissipation and junction temperature for
AME1084 in TO-220 package are given by
R1
(Connect R1 to case)
RL
PD = (VIN - VOUT) x IOUT
R2
TJUNCTION = TAMBIENT + ( PD x qJA)
Note: TJUNCTION must not exceed 125oC
Connect
R2 to load
12
Rev.N.02
AME [ ANALOG MICROELECTRONICS ]
