Analog Microelectronics, Inc.
5A Low Dropout
Positive Voltage Regulator
AME1084
3. Current limit protection
n Application Description
AME1084 is protected against overload conditions.
Current protection is triggered at typical 7.5A.
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 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:
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 10µF tantalum or 50µF aluminum
electrolytic is sufficient.
Note: It is important that the ESR for this capacitor
does not exceed 0.5Ω.
R2
VOUT = VREF ( 1 +
) + IADJ x R2
R1
The output capacitor dose not have a theoretical
upper limit and increasing its value will increase
stability. COUT = 100µF or more is typical for high cur-
rent regulator design.
On fixed versions of AME1084, the voltage di-
vider is provided internally.
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, RP is not multiplied
by the divider ratio.
VOUT
VIN
IN
O U T
ADJ
VREF
R1
R2
C1
IADJ
50
µ
A
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.
R2
R1
) + IADJ x R2
VOUT = VREF (1+
RP
Parasitic
Line Resistance
Figure 3
VIN
IN
OUT
ADJ
2. Thermal protection
R1
RL
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.
(Connect R1 to case)
R2
The power dissipation and junction tempera-
ture for AME1084 in TO-220 package are given
by
Connect
PD = (VIN - VOUT) x IOUT
R2 to load
TJUNCTION = TAMBIENT + ( PD x θJA)
Note: TJUNCTION must not exceed 125OC
Figure 4
6
AME [ ANALOG MICROELECTRONICS ]
