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Austin Semiconductor, Inc. Low Dropout Regulator
AVAILABLE AS MILITARY SPECIFICATIONS
* Military Equipment Screening - MIL-STD-883, 1.2.2
LOW DROPOUT REGULAT REGULATOR
AS1185
(Top View)
PIN ASSIGNMENT
10 Lead Flat Pack (F)
GND FB VIN VREF VIN 1 2 3 4 5 10 9 8 7 6 GND VOUT NC VOUT NC
FEATURES
* Low Resistance Pass Transistor: 0.25 * Dropout Voltage: 0.75V at 2.7A * 1% Reference Voltage * Accurate Programmable Current Limit * Shutdown Capability * Internal Reference Available * Standard 10-Lead Packages * Full Remote Sense * Low Quiescent Current: 2.5mA * Good High Frequency Ripple Rejection
OPTIONS
* Packages 10 Lead Ceramic Flatpack
MARKINGS
F
5V, 2.7A Regulator with 2.7A current limit
GENERAL DESCRIPTION
The AS1185 is a 2.7A low dropout regulator with adjustable current limit and remote sense capability. It can be used as a positive output regulator with floating input or as a standard negative regulator with grounded input. The output voltage range is 2.5V to 25V, with 1% accuracy on the internal reference voltage. The AS1185 uses a saturation-limited NPN transistor as the pass element. This device gives the linear dropout characteristics of a FET pass element with significantly less die area. High efficiency is maintained by using special anti-saturation circuitry that adjusts base drive to track load current. The "on resistance" is typically 0.25. Accurate current limit is programmed with a single 1/8W external resistor, with a range of zero to three amperes. A second, fixed internal limit circuit prevents destructive currents 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 1A, 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 RATINGS1
LOW DROPOUT REGULAT REGULATOR
AS1185
Input Voltage ..................................................................................................................................................................................................... 35V Input-Output Differential ................................................................................................................................................................................. 30V FB Voltage .......................................................................................................................................................................................................... 7V REF Voltage ........................................................................................................................................................................................................ 7V Output Voltage .................................................................................................................................................................................................. 30V Output Reverse Voltage .................................................................................................................................................................................. 2V Operating Ambient Temperature Range AS1185M ........................................................................................................................................................................... -55C to 125C Operating Junction Temperature Range Control Section AS1185/IT ......................................................................................................................................................................... -40C to 125C AS1185M/XT and /Mil .................................................................................................................................................. -55C to 150C Power Transistor Section AS1185/IT ........................................................................................................................................................................ -40C to 150C AS1185M/XT and /MIL.................................................................................................................................................. -55C to 175C Storage Temperature Range .......................................................................................................................................................... -65C to 150C Lead Temperature (Soldering, 10 sec)........................................................................................................................................................... 300C Theta J/C................................................................................................................................................................................................8.11C/W Max Power Dissipation (Tc = +125C).......................................................................................................................................................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, 25C) 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; VDROPOUT = 0.25V + 0.25W * IOUT. 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, RLIM, 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. TJMIN = - 40C for AS1185I and -55C for the AS1185M. Power transistor area and control circuit area have different maximum junction temperatures. Control area limits are TJMAX = 125C for the LT1185C and LT1185I and 150C for the LT1185M. Power area limits are 150C for AS1185I and 175C for AS1185M. 10. VSAT is the maximum specified dropout voltage; 0.25V + 0.25 * IOUT. 11. Current limit is programmed with a resistor from REF pin to GND pin. The value is 15k/ILIM. 12. For VIN - VOUT = 1.5V; VIN = 5V, VOUT = 3.5V. VOUT = 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 TA = 25C. Adjustable version, VIN = 7.4V, VOUT = 5V, IOUT = 1mA, RLIM = 5.6k, unless otherwise noted.
PARAMETER Reference Voltage (@ FB Pin) CONDITION VIN - VOUT = 5V, VOUT = VREF 1mA < IOUT < 2.7A VIN - VOUT = 1.2V to VIN = 30V P < 25W6, VOUT = 5V Feedback Pin Bias Current Dropout Voltage3 Load Regulation7 Line Regulation7 Minimum Input Voltage TMIN < TJ < VOUT = VREF IOUT = 0.5A, VOUT = 5V IOUT = 2.7A, VOUT = 5V IOUT = 5mA to 2.7A VIN - VOUT = 1.5V to 10V, VOUT = 5V VIN - VOUT = 1V to 20V, VOUT = 5V IOUT = 1A4, VOUT = VREF IOUT = 2.7A 1.5V < VIN - VOUT < 10V VIN - VOUT = 15V VIN - VOUT = 20V VIN - VOUT = 30V 5k < RLIM < 15k, VOUT = 1V11 1A < ILIM < 2.7A RLIM = 15k * A/ILIM IOUT = 5mA, VOUT = VREF 4V < VIN < 25V5 VIN - VOUT = VSAT10 VIN - VOUT > 2V VIN - VOUT = 10V, IOUT = 5mA to 2A
8
MIN
TYP 2.37 0.3
MAX 1
UNITS V %
Rference Voltage Tolerance (@ FB Pin)2
*
1
2.5
%
TMAX9
*
0.7 0.20 0.67 0.05 0.002 4.0 4.3 3.6 3 1.7 0.4 15k 0.02 ILIM 0.04 ILIM 2.5 25 10 2 0.005 0.003
2.0 0.37 1.00 0.3 0.01
A 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 Coefficient8
* * * * *
0.06 ILIM + 0.03 0.09 ILIM + 0.05 3.5 40 25 7 0.014 0.01
A A mA mA/A mA/A A %/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: (VOUT - 2.37) R1 VREF
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 VREF = 2.37V, this reduces to: R2 = VOUT - 2.37k suggested values of 1% resistors are shown.
VOUT 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.
5
Austin Semiconductor, Inc.
LOW DROPOUT REGULAT REGULATOR
AS1185
MECHANICAL DEFINITIONS*
Package Designator F
SYMBOL A B C D E F G H I
ASI SPECIFICATIONS MIN MAX 0.250 0.260 0.250 0.260 0.900 --0.100 0.110 0.155 0.165 0.004 0.006 0.032 0.043 0.015 0.019 0.047 0.053
*All measurements are in inches.
AS1185 Rev. 1.1 6/05
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
6
Austin Semiconductor, Inc.
LOW DROPOUT REGULAT REGULATOR
AS1185
ORDERING INFORMATION
EXAMPLE:
AS1185F/MIL
Device Number Package Type Process AS1185 F /*
*AVAILABLE PROCESSES IT = Industrial Temperature Range XT = Extended Temperature Range MIL = /883 equivalent processing compliant to paragraph 1.2.2 SPACE = ASI's DSCC approved V-level/Class S (Space) Manufacturing Flow
-40oC to +85oC -55oC to +125oC -55oC to +125oC -55oC to +125oC
AS1185 Rev. 1.1 6/05
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
7

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