Analog Microelectronics, Inc.
AME1117
1A Low Dropout Positive
Voltage Regulator
n
Application Descriptions
1. Output voltage adjustment
Like most regulators, the AME1117 regulates the
output by comparing the output voltage to an inter-
nally generated reference voltage. On the adjust-
able version, the V
REF
is available externally 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:
V
O U T
= V
R EF
(1+ R2 ) + I
AD J
x R2
R1
3. Current Limit Protection
AME1117 is protected against overload conditions.
Current protection is triggered at typically 1.5A.
4. Stability and Load Regulation
AME1117 requires a capacitor from V
OUT
to GND
to provide compensation feedback to the internal
gain stage. This is to ensure stability at the output
terminal. Typically, a 10µF tantalum or 50µF alu-
minum electrolytic is sufficient.
Note: It is important that the ESR for this
capacitor does not exceed 0.5Ω.
The output capacitor does not have a theoretical
upper limit and increasing its value will increase
stability. C
OUT
= 100µF or more is typical for high
current regulator design.
For the adjustable version, the best load regulation
is accomplished when the top of the resistor di-
vider (R1) is connected directly to the output pin of
the AME1117. When so connected, R
P
is not mul-
tiplied by the divider ratio.
For fixed output versions, the top of R1 is internally
connected to the output. The ground pin can be
connected to the low side of the load in order to
eliminate ground loop errors.
R
P
Parasitic
Line Resistance
V
IN
IN
ADJ
R1
(Connect
R1 to case)
R2
R
L
OUT
On fixed versions of AME1117, the voltage divider
is provided internally.
V
IN
C
1
IN
ADJ
I
A D J
50
µA
OUT
V
REF
R1
V
OUT
R2
V
O U T
= V
R E F
(1+ R2 ) + I
A D J
x R2
R1
Figure 4
2. Thermal protection
AME1117 has thermal protection which limits
junction temperature to 150
O
C. However, device
functionality is only guaranteed to a maximum
junction temperature of +125
O
C.
The power dissipation and junction temperature
for AME1117 in DPAK 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
Connect
R2 to load
Figure 5
9
AME [ ANALOG MICROELECTRONICS ]
