Analog Microelectronics, Inc.
AME1085
3A Low Dropout
Positive Voltage Regulator
n General Description
The AME1085 is a 3A low-dropout positive voltage regulator. It is available in fixed and adjustable output voltage versions. Overcurrent and thermal protection are integrated 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.
n Key Features
lLow dropout voltage 1.2V typically at 3A
lAdjustable or 3.3V fixed voltage
lLine regulation typically 0.015%
lLoad regulation typically 0.05%
lAdjust pin (ADJ) current less than 90υA
lOvercurrent protection
lThermal protection
lAvailable in TO-220, TO-263, TO-252
n Applications
lHigh Efficiency Linear Regulators
lPost Regulators for Switching Supplies
l5V to 3.3V Voltage Converter
lBattery Charger
n Functional Block Diagram
Input
Current
Limiting
Amplifier
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Thermal |
Output |
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Protection |
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Error
Amp. Bandgap ADJ/GN D
Reference
Figure 1
n Typical Application
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AME1085 |
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V IN |
V O U T |
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GND |
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4.75V to 5.25V |
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10μF Tan |
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10μF Tan Load |
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Figure 2
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
A D J / G N D V O U T V IN |
A D J / G N D V O U T V IN |
To-252-2 Front View |
TO-252-2 Front view |
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AME1085
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AME 1085 |
1 |
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3 |
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ADJ/ |
VOUT |
VIN |
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A D J / G N D V O U T |
V IN |
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GND |
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2
Analog Microelectronics, Inc.
AME1085
3A Low Dropout
Positive Voltage Regulator
n Ordering Information
Part Number |
Marking |
Output Voltage |
Package |
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AME1085 |
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AME1085ACBT |
ACBT |
ADJ |
TO-220 |
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YYWW |
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AME1085 |
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AME1085DCBT |
DCBT |
3.3 |
TO-220 |
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YYWW |
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AME1085 |
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AME1085ACDT-3 |
ACDT-3 |
ADJ |
TO-263-3 |
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YYWW |
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AME1085 |
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AME1085DCDT-3 |
DCDT-3 |
3.3 |
TO-263-3 |
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YYWW |
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AME1085 |
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AME1085ACDT |
ACDT |
ADJ |
TO-263-2 |
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YYWW |
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AME1085 |
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AME1085DCDT |
DCDT |
3.3 |
TO-263-2 |
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YYWW |
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AME1085 |
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AME1085AMCT |
AMCT |
ADJ |
TO-252-2 |
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YYWW |
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AME1085 |
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AME1085MCT* |
MCT |
3.3 |
TO-252-2 |
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YYWW |
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* This differs from our standard part numbering scheme due to historical precedent
n Absolute Maximum Ratings
Parameter |
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Symbol |
Maximum |
Units |
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Input Voltage |
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VIN |
7 |
V |
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Thermal Resistance |
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TO-220 |
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2.5 |
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TO-263 |
θJC |
2.5 |
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(Junction to Case) |
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TO-252 |
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15 |
0C/W |
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Thermal Resistance |
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TO-220 |
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50 |
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TO-263 |
θJA |
60 |
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(Junction to Ambient) |
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TO-252 |
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90 |
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Operating Junction Temperature Range |
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TJ |
0 to 125 |
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Storage Temperature Range |
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TSTG |
-65 to 150 |
0C |
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Lead Temperature ( 10 sec ) |
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TLEAD |
260 |
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3
Analog Microelectronics, Inc.
AME1085
3A Low Dropout
Positive Voltage Regulator
n Electrical Characteristics
AME1085AXXX
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Parameter |
Symbol |
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Test Conditions |
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Min. |
Typ. |
Max. |
Units |
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Reference voltage |
VREF |
VIN = 5V |
TJ =250C |
1.238 |
1.250 |
1.262 |
V |
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(adjustable voltage) |
IO = 10mA |
Over temp. |
1.225 |
1.275 |
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V |
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= 2.75 - 7V |
T =250C |
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0.015 |
0.2 |
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Line regulation |
RegLINE |
IN |
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J |
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% |
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I |
= 10mA |
Over temp. |
- |
0.035 |
0.2 |
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Load regulation |
RegLOAD |
VIN = 5V |
TJ =250C |
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0.05 |
0.3 |
% |
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I |
= 10mA - 3A |
Over temp. |
- |
0.2 |
0.4 |
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O |
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Dropout voltage |
VD |
VIN = 2.75 - 7V |
TJ =250C |
- |
1.2 |
1.4 |
V |
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VOUT, |
VREF = 1% |
IO = 10mA - 3A |
Over temp. |
- |
1.3 |
- |
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Current limit |
IS |
VIN = 2.75 - 7V, Over temp. |
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3.0 |
- |
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A |
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Temperature Coefficient |
TC |
VIN = 2.75 - 7V, IO = 10mA - 3A |
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0.005 |
- |
%/OC |
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Temperature stability |
TS |
VIN = 5V, IO = 500mA, Over temp. |
- |
0.5 |
- |
% |
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Minimum load current |
IO |
VIN = 5V |
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5 |
10 |
mA |
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RMS output noise |
VN |
TJ =250C |
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0.003 |
- |
%V0 |
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Ripple rejection ratio |
RA |
VIN = 5V, IO = 3A, Over temp. |
60 |
72 |
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dB |
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AME1085DXXX |
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Parameter |
Symbol |
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Test Conditions |
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Min. |
Typ. |
Max. |
Units |
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Output voltage |
Vo |
VIN = 5V |
TJ =250C |
3.267 |
3.300 |
3.333 |
V |
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(fixed voltage) |
IO = 0A |
Over temp. |
3.234 |
3.366 |
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V |
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=4.5 - 7V |
T =250C |
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0.015 |
0.2 |
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Line regulation |
RegLINE |
IN |
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J |
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% |
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I |
= 0A |
Over temp. |
- |
0.035 |
0.2 |
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O |
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Load regulation |
RegLOAD |
VIN = 5V |
TJ =250C |
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0.05 |
0.3 |
% |
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I |
= 0A - 3A |
Over temp. |
- |
0.2 |
0.4 |
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O |
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Dropout voltage |
VD |
VIN = 4.5 - 7V |
TJ =250C |
- |
1.2 |
1.4 |
V |
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VOUT, |
VREF = 1% |
IO = 0A - 3A |
Over temp. |
- |
1.3 |
- |
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Current limit |
IS |
VIN = 4.5 - 7V, Over temp. |
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3.0 |
- |
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A |
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Quiescent current |
IQ |
VIN = 5V, Io=0A - 3A, Over temp. |
- |
12 |
13 |
mA |
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Temperature Coefficient |
TC |
VIN = 4.5 - 7V, IO = 0A - 3A |
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0.005 |
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%/0C |
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Temperature stability |
TS |
VIN = 5V, IO = 500mA, Over temp. |
- |
0.5 |
- |
% |
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RMS output noise |
VN |
TJ =250C |
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0.003 |
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%V0 |
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Ripple rejection ratio |
RA |
VIN = 5V, IO = 3A, Over temp. |
60 |
72 |
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dB |
4
Analog Microelectronics, Inc.
AME1085
3A Low Dropout
Positive Voltage Regulator
nApplication 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 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:
VOUT = VREF ( 1 + R2 ) + IADJ x R2 R1
On fixed versions of AME1085, the voltage divider is provided internally.
VIN |
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IN |
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O U T |
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VO U T |
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C 1 |
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ADJ |
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VREF |
R1 |
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IADJ |
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50μA |
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R2 |
V |
O U T |
= V |
REF |
(1+ |
R2 ) + I |
ADJ |
x R2 |
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R1 |
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Figure 3 |
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VIN |
3.Current limit protection
AME1085 is protected against overload conditions. Current protection is triggered at typically 4.5A.
4.Stability and load regulation
AME1085 requires a capacitor from VOUT 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 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 theoreti-
cal upper limit and increasing its value will increase stability. COUT = 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 divider (R1) is connected directly to the output pin of the AME1085. When so con-
nected, RP is not multiplied by the divider ratio. For fixed output versions, the top of R1 is internally connected to the output and ground pin can be connected to low side of the load.
R P
Parasitic
Line Resistance
IN O U T
ADJ
2.Thermal protection
AME1085 has thermal protection which limits junction temperature to 150OC. However, de-
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functionality is only guaranteed to a maxi- |
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junction temperature of +125OC. |
The power dissipation and junction temperature for AME1085 in TO-220 package are given by
R1
R L
(Connect R1 to case)
R2
PD = (VIN - VOUT) x IOUT |
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Connect |
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x θJA) |
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TJUNCTION = TAMBIENT + ( PD |
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R2 to load |
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Note: TJUNCTION must not exceed 125OC
Figure 4
5