Analog Microelectronics, Inc.
AME1085
3A Low Dropout
Positive Voltage Regulator
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General Description
The AME1085 is a 3A low-dropout positive voltage regu-
lator. It is available in fixed and adjustable output voltage
versions. Overcurrent and thermal protection are inte-
grated onto the chip. Output current will limit as it reaches
the pre-set current or temperature limit. At full rated
output current the dropout voltage is 1.4V (max.).
AME1085 series regulators provide excellent regulation
over line, load and temperature variations.
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Key Features
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Low dropout voltage 1.2V typically at 3A
Adjustable or 3.3V fixed voltage
Line regulation typically 0.015%
Load regulation typically 0.05%
Adjust pin (ADJ) current less than 90υA
Overcurrent protection
Thermal protection
Available in TO-220, TO-263, TO-252
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Applications
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High Efficiency Linear Regulators
Post Regulators for Switching Supplies
5V to 3.3V Voltage Converter
Battery Charger
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Functional Block Diagram
Input
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Typical Application
AME1085
V
IN
GND
V
OUT
Current
Limiting
Amplifier
Thermal
Protection
Output
4.75V to 5.25V
10µF Tan
10µF Tan
L o a d
Error
Amp.
Bandgap
Reference
ADJ/GND
Figure 2
Figure 1
1
Analog Microelectronics, Inc.
AME1085
3A Low Dropout
Positive Voltage Regulator
n
Pin Configuration
To-263 Front View
To-263-2 Front View
AME 1085
1
2
3
AME 1085
1
2
3
ADJ/GND V
OUT
V
IN
ADJ/GND V
OUT
V
IN
To-252-2 Front View
TO-252-2 Front view
AME1085
AME 1085
1
2
3
1
ADJ/
GND
2
V
OUT
3
ADJ/GND V
OUT
V
IN
V
IN
2
Analog Microelectronics, Inc.
AME1085
3A Low Dropout
Positive Voltage Regulator
n
Ordering Information
Part Number
AME1085ACBT
Marking
AME1085
ACBT
YYWW
AME1085
DCBT
YYWW
AME1085
ACDT-3
YYWW
AME1085
DCDT-3
YYWW
AME1085
ACDT
YYWW
AME1085
DCDT
YYWW
AME1085
AMCT
YYWW
AME1085
MCT
YYWW
Output Voltage
ADJ
Package
TO-220
AME1085DCBT
3.3
TO-220
AME1085ACDT-3
ADJ
TO-263-3
AME1085DCDT-3
3.3
TO-263-3
AME1085ACDT
ADJ
TO-263-2
AME1085DCDT
3.3
TO-263-2
AME1085AMCT
ADJ
TO-252-2
AME1085MCT*
3.3
TO-252-2
* This differs from our standard part numbering scheme due to historical precedent
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Absolute Maximum Ratings
Parameter
Input Voltage
Thermal Resistance
(Junction to Case)
Thermal Resistance
(Junction to Ambient)
Operating Junction Temperature Range
Storage Temperature Range
Lead Temperature ( 10 sec )
TO-220
TO-263
TO-252
TO-220
TO-263
TO-252
T
J
T
STG
T
LEAD
θ
JA
Symbol Maximum
V
IN
θ
JC
7
2.5
2.5
15
50
60
90
0 to 125
-65 to 150
260
Units
V
0
C/W
0
C
3
Analog Microelectronics, Inc.
AME1085
3A Low Dropout
Positive Voltage Regulator
n
Electrical Characteristics
AME1085AXXX
Parameter
Reference voltage
(adjustable voltage)
Line regulation
Load regulation
Dropout voltage
∆
V
OUT
,
∆
V
REF
= 1%
Current limit
Temperature Coefficient
Temperature stability
Minimum load current
RMS output noise
Ripple rejection ratio
Symbol
V
REF
Reg
LINE
Reg
LOAD
V
D
I
S
T
C
T
S
I
O
V
N
R
A
V
IN
= 5V
I
O
= 10mA
V
IN
= 2.75 - 7V
I
O
= 10mA
V
IN
= 5V
I
O
= 10mA - 3A
V
IN
= 2.75 - 7V
I
O
= 10mA - 3A
V
IN
= 2.75 - 7V, Over temp.
V
IN
= 2.75 - 7V, I
O
= 10mA - 3A
V
IN
= 5V, I
O
= 500mA, Over temp.
V
IN
= 5V
T
J
=25
0
C
V
IN
= 5V, I
O
= 3A, Over temp.
Test Conditions
T
J
=25 C
T
J
=25
0
C
Over temp.
T
J
=25
0
C
Over temp.
T
J
=25
0
C
Over temp.
0
Min.
1.238
-
-
-
-
-
-
3.0
-
-
-
-
60
Typ.
1.250
0.015
0.035
0.05
0.2
1.2
1.3
-
0.005
0.5
5
0.003
72
Max.
1.262
1.275
0.2
0.2
0.3
0.4
1.4
-
-
-
-
10
-
-
Units
V
%
%
V
A
%/
O
C
%
mA
%V
0
dB
Over temp. 1.225
AME1085DXXX
Parameter
Output voltage
(fixed voltage)
Line regulation
Load regulation
Dropout voltage
∆
V
OUT
,
∆
V
REF
= 1%
Current limit
Quiescent current
(fixed model)
Temperature Coefficient
Temperature stability
RMS output noise
Ripple rejection ratio
Symbol
Vo
Reg
LINE
Reg
LOAD
V
D
I
S
I
Q
T
C
T
S
V
N
R
A
V
IN
= 5V
I
O
= 0A
V
IN
=4.5 - 7V
I
O
= 0A
V
IN
= 5V
I
O
= 0A - 3A
V
IN
= 4.5 - 7V
I
O
= 0A - 3A
V
IN
= 4.5 - 7V, Over temp.
V
IN
= 5V, Io=0A - 3A, Over temp.
V
IN
= 4.5 - 7V, I
O
= 0A - 3A
V
IN
= 5V, I
O
= 500mA, Over temp.
T
J
=25
0
C
V
IN
= 5V, I
O
= 3A, Over temp.
Test Conditions
T
J
=25 C
T
J
=25
0
C
Over temp.
T
J
=25
0
C
Over temp.
T
J
=25
0
C
Over temp.
0
Min.
3.267
-
-
-
-
-
-
3.0
-
-
-
-
60
Typ.
3.300
0.015
0.035
0.05
0.2
1.2
1.3
-
12
0.005
0.5
0.003
72
Max.
3.333
3.366
0.2
0.2
0.3
0.4
1.4
-
-
13
-
-
-
-
Units
V
%
%
V
A
mA
%/
0
C
%
%V
0
dB
Over temp. 3.234
4
Analog Microelectronics, Inc.
AME1085
3A Low Dropout
Positive Voltage Regulator
3. Current limit protection
AME1085 is protected against overload condi-
tions. Current protection is triggered at typi-
cally 4.5A.
4. Stability and load regulation
AME1085 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 tanta-
lum or 50µF aluminum electrolytic is sufficient.
Note: It is important that the ESR for this ca-
pacitor does not exceed 0.5Ω.
The output capacitor dose not have a theoreti-
cal upper limit and increasing its value will in-
crease stability. C
OUT
= 100µF or more is typi-
cal for high current regulator design.
V
OUT
V
REF
R1
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Application Description
1. Output voltage adjustment
Like most regulators, the AME1085 regulates the
output by comparing the output voltage to an
internally generated reference voltage. On the
adjustable version, the V
REF
is available exter-
nally 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 AME1085, the voltage di-
vider is provided internally.
V
IN
C
1
IN
ADJ
I
A DJ
50µA
OUT
R2
V
O U T
= V
R E F
(1+ R 2 ) + I
ADJ
x R2
R1
V
IN
For the adjustable version, the best load regu-
lation is accomplished when the top of the
resistor divider (R1) is connected directly to the
output pin of the AME1085. When so con-
nected, R
P
is not multiplied by the divider ratio.
For fixed output versions, the top of R1 is in-
ternally connected to the output and ground
pin can be connected to low side of the load.
R
P
Parasitic
Line Resistance
IN
ADJ
OUT
Figure 3
2. Thermal protection
AME1085 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 temperature
for AME1085 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
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