if the programming current is accidentally overranged.
Assembly considerations for this package requires that
the fixed internal current limit circuit be bypassed at all times.
An external current limit resistor set to a maximum of 2.7A
must be used. Failure to do so on this package can result in
damage to the device.
Shutdown of the regulator output is guaranteed when the
program current is less than 1µA, allowing external logic
control of output voltage.
5.6K
AS1185
For more products and information
please visit our web site at
www.austinsemiconductor.com
AS1185
Rev. 1.1 6/05
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
1
Austin Semiconductor, Inc.
ABSOLUTE MAXIMUM RATINGS
1
LOW DROPOUT
REGULAT
REGULATOR
AS1185
Input Voltage ..................................................................................................................................................................................................... 35V
FB Voltage .......................................................................................................................................................................................................... 7V
REF Voltage ........................................................................................................................................................................................................ 7V
Output Voltage .................................................................................................................................................................................................. 30V
Output Reverse Voltage .................................................................................................................................................................................. 2V
Operating Ambient Temperature Range
AS1185M ........................................................................................................................................................................... -55°C to 125°C
Operating Junction Temperature Range
Control Section
AS1185/IT ......................................................................................................................................................................... –40°C to 125°C
AS1185M/XT and /Mil .................................................................................................................................................. –55°C to 150°C
Power Transistor Section
AS1185/IT ........................................................................................................................................................................ –40°C to 150°C
AS1185M/XT and /MIL.................................................................................................................................................. –55°C to 175°C
Storage Temperature Range .......................................................................................................................................................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)........................................................................................................................................................... 300°C
Max Power Dissipation (Tc = +125°C).......................................................................................................................................................3.0W
NOTES:
1. Stresses greater than those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only
and functional operation of the device at these or any other conditions above those indicated in the operation section of this specification is not
implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
2. Reference voltage is quaranteed both at nominal conditions (no load, 25°C) and at worst-case conditions of load, line, power, and temperature.
An intermediate value can be calculated by adding the effects of these variables in the actual application.
3. Dropout voltage is tested by reducing input voltage until the output drops 1% below its nominal value. Tests are done at 0.5A and 2.7A. The
power transistor looks basically like a pure resistance in this range so that minimum differential at any intermediate current can be calculated by
interpolation; V
DROPOUT
= 0.25V + 0.25W • I
OUT
. For load current less than 0.5A, see graph.
4. “Minimum input voltage” is limited by base emitter voltage drive of the power transistor section, not saturation as measured in Note 3. For
output voltages below 4V, “minimum input voltage” specification may limit dropout voltage before transistor saturation limitation.
5. Supply current is measured on the ground pin, and does not include load current, R
LIM
, or output divider current.
6. The 25W power level is guaranteed for an input-output voltage of 8.3V to 17V. At lower voltages the 2.7A limit applies, and at higher voltages
the internal power limiting may restrict regulator power below 25W. See graphs.
7. Line and load regulation are measured on a pulse basis with a pulse width of »2ms, to minimize heating. DC regulation will be affected by thermal
regulation and temperature coefficient of the reference.
8. Guaranteed by design and correlation to other tests, but not tested.
9. T
JMIN
= – 40°C for AS1185I and –55°C for the AS1185M. Power transistor area and control circuit area have different maximum junction
temperatures. Control area limits are T
JMAX
= 125°C for the LT1185C and LT1185I and 150°C for the LT1185M. Power area limits are 150°C for
AS1185I and 175°C for AS1185M.
10. V
SAT
is the maximum specified dropout voltage; 0.25V + 0.25 • I
OUT
.
11. Current limit is programmed with a resistor from REF pin to GND pin. The value is 15k/I
LIM
.
12. For V
IN
– V
OUT
= 1.5V; V
IN
= 5V, V
OUT
= 3.5V. V
OUT
= 1V for all other current limit tests.
AS1185
Rev. 1.1 6/05
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
2
Austin Semiconductor, Inc.
LOW DROPOUT
REGULAT
REGULATOR
AS1185
ELECTRICAL CHARACTERISTICS:
The • denotes specifications which apply over the
operating temperature range, otherwise specifications are at T
A
= 25°C. Adjustable version,
V
IN
= 7.4V, V
OUT
= 5V, I
OUT
= 1mA, R
LIM
= 5.6k, unless otherwise noted.
PARAMETER
Reference Voltage (@ FB Pin)
CONDITION
V
IN
- V
OUT
= 5V, V
OUT
= V
REF
1mA < I
OUT
< 2.7A
V
IN
- V
OUT
= 1.2V to V
IN
= 30V
P < 25W
6
, V
OUT
= 5V
Feedback Pin Bias Current
Dropout Voltage
3
Load Regulation
7
Line Regulation
7
Minimum Input Voltage
T
MIN
< T
J
< T
MAX9
V
OUT
= V
REF
I
OUT
= 0.5A, V
OUT
= 5V
I
OUT
= 2.7A, V
OUT
= 5V
I
OUT
= 5mA to 2.7A
V
IN
- V
OUT
= 1.5V to 10V, V
OUT
= 5V
V
IN
- V
OUT
= 1V to 20V, V
OUT
= 5V
I
OUT
= 1A , V
OUT
= V
REF
I
OUT
= 2.7A
1.5V < V
IN
- V
OUT
< 10V
V
IN
- V
OUT
= 15V
V
IN
- V
OUT
= 20V
V
IN
- V
OUT
= 30V
5k < R
LIM
< 15k, V
OUT
= 1V
11
1A < I
LIM
< 2.7A
R
LIM
= 15k • A/I
LIM
I
OUT
= 5mA, V
OUT
= V
REF
4V < V
IN
< 25V
5
V
IN
- V
OUT
= V
SAT10
V
IN
- V
OUT
> 2V
V
IN
- V
OUT
= 10V, I
OUT
= 5mA to 2A
8
•
•
•
•
•
4
MIN
TYP
2.37
0.3
MAX
±1
UNITS
V
%
Rference Voltage Tolerance (@ FB Pin)
2
•
1
±2.5
%
•
0.7
0.20
0.67
0.05
0.002
4.0
4.3
3.6
3
1.7
0.4
15k
0.02 I
LIM
0.04 I
LIM
2.5
25
10
2
0.005
0.003
2.0
0.37
1.00
0.3
0.01
µA
V
V
%
%/V
V
V
A
A
A
A
A
A•W
Internal Current Limit
(See Graph for Guaranteed Curve)
8, 12
3.3
3.1
2.0
1.0
0.2
4.2
4.4
4.2
2.6
1.0
External Current Limit Programming
Constant
External Current Limit Error
Quiescent Supply Current
Supply Current Change with Load
REF Pin Shutoff Current
Thermal Regulation
(See Applications Information)
Reference Voltage Temperature
Coefficient
8
•
•
•
•
•
0.06 I
LIM
+ 0.03
0.09 I
LIM
+ 0.05
3.5
40
25
7
0.014
0.01
A
A
mA
mA/A
mA/A
µA
%/W
%/°C
0.4
AS1185
Rev. 1.1 6/05
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
3
Austin Semiconductor, Inc.
SETTING OUTPUT VOLTAGE
The AS1185 output voltage is set by two external resistors
(see Figure 2). Internal reference voltage is trimmed to 2.37V so
that a standard 1% 2.37k resistor (R1) can be used to set divider
current at 1mA. R2 is then selected from:
(V
OUT
- 2.37) R1
V
REF
LOW DROPOUT
REGULAT
REGULATOR
AS1185
R2 =
External Current Limit
The AS1185 requires a resistor to set current limit. The value
of this resistor is 15k divided by the desired current limit (in
amps). The resistor for 2A current limit would be 15k/2A = 7.5k.
Tolerance over temperature is ±10%, so current limit is normally
set 15% above maximum load current. Foldback limiting can be
employed if short-circuit current must be lower than full load
current (see Typical Applications).
The AS1185 has internal current limiting which will override
external current limit if power in the pass transistor is
excessive. The internal limit is
≈
3.6A with a foldback
characteristic which is dependent on input-output voltage, not
output voltage
per se
(see Typical Performace Characteristics).
Assembly considerations for this package requires that
the fixed internal current limit circuit be bypassed at all times.
An external current limit resistor set to a maximum of 2.7A
must be used. Failure to do so on this package can result in
damage to the device.
for R1 = 2.37k and V
REF
= 2.37V, this reduces to:
R2 = V
OUT
- 2.37k
suggested values of 1% resistors are shown.
V
OUT
5V
5.2V
6V
12V
15V
R2 WHEN R1 = 2.37k
2.67k
2.87k
3.65k
9.76k
12.7k
AS1185
Rev. 1.1 6/05
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
4
Austin Semiconductor, Inc.
TYPICAL PERFORMANCE CHARACTERISTICS
LOW DROPOUT
REGULAT
REGULATOR
AS1185
AS1185
Rev. 1.1 6/05
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
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