PD-97330
Adjustable Low Dropout
Positive Voltage Regulator
Product Summary
Part Number
OM185ST
OM185ST
V
ADJ
,
3.0A
Output Voltage
Adjustable
Output Current
3.0A
Package
TO-257AA
TO-257AA
Description
These three terminal positive adjustable voltage
regulators are designed to provide 3.0A with higher
efficiency than conventional voltage regulators. The
devices are designed to operate to 1.5V input to
output differential and the dropout voltage is
specified as a function of load current. Devices are
pin compatible with older three terminal regulators
and are supplied in the easy-to-use hermetic metal
TO-257 package. These devices are ideally suited
for Military applications where small size, hermeticity
and high reliability are required.
Features
n
Operates Down to 1.0V Dropout @ Max Current
n
0.015% Line Regulation
n
0.01% Load Regulation
n
1% Reference Voltage
n
Hermetic TO-257AA (Isolated Tab) Package
n
Electrically Equivalent to LM1085
n
This part is also available in
D2 Package as OM185SR
Absolute Maximum Ratings @ T
C
= 25°C
Parameter
Output Current
Differential Voltage
Thermal Resistance, Junction to Case
Operating Junction Temperature Range
Storage Temperature Range
Symbol
I
O
V
DIFF
R
θJC
T
J
T
STG
Value
3.0
29
4.2
-55 to +150
-65 to +150
Units
A
V
°C/W
°C
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06/24/08
OM185ST
Electrical Characteristics
Ã
T
J
= 25°C (Unless Otherwise Specified)
Parameter
Reference Voltage
Line Regulation
Load Regulation
Dropout Voltage
Current Limit
Test Conditions
I
OUT
= 10mA, (V
IN
- V
OUT
) = 3.0V
10mA
≤
I
OUT
≤
I
FULL LOAD
, 1.5V
≤
(V
IN
- V
OUT
)
≤
25V
I
LOAD
= 10mA, 1.5V
d
(V
IN
- V
OUT
)
dÃ
15V
Min.
Typ.
1.250
1.250
0.015
0.035
0.5
0.8
1.3
-
-
5.0
0.004
75
55
0.2
0.5
0.3
Max.
1.262
1.270
0.2
0.2
0.8
1.0
1.5
-
-
10
0.02
-
-
5.0
-
1.0
Units
V
e
1.238
1.220
-
-
-
-
-
3.0
0.2
-
-
60
-
cd
(V
IN
- V
OUT
) = 3.0V, 10mA
dÃ
I
OUT
ÃdÃ
I
FULL LOAD
%
U
V
REF
= 1%, I
OUT
= I
FULL LOAD
f
(V
IN
- V
OUT
) = 5.0V
(V
IN
- V
OUT
) = 25V
cde
V
A
mA
%/W
dB
Minimum Load Current (V
IN
- V
OUT
) = 25V
Thermal Regulation
Ripple Rejection
Adjust Pin Current
Adjust Pin Current
Change
Temperature Stability
Long Term Stability
10mA
≤
I
OUT
≤
I
FULL LOAD
1.5V
≤
(V
IN
- V
OUT
)
≤
25V
-55°C
≤
T
J
≤
+150°C
T
J
= 125°C, t = 1000hrs
30ms Pulse Width (Guaranteed by design)
f = 120Hz, C
Adj
= 25
F Tantalum
I
OUT
- I
FULL LOAD
(V
IN
- V
OUT
) = 3.0V
-
-
-
µA
%
Notes
1. Load and line regulation are measured at a constant junction temperature by low duty cycle pulse testing.
2. Line and load regulation are guaranteed up to the maximum power dissipation. Power dissipation is determined by
the input/output differential voltage and output current. Guaranteed maximum power dissipation will not be available
over the full input/output voltage range.
3. I
FULL LOAD
curve is defined as the minimum value of current limit as a function of input to output voltage. Note that
power dissipation is only achievable over a limited range of input to output voltage.
4. Dropout voltage is specified over the full output current range of the device.
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OM185ST
Dropout Voltage
Short Circuit Current
Fig 1:
Typical Minimum Input/Output
Differential Vs Output Current
Fig 2:
Typical Short Circuit Current
Vs Input/Output Differential
Load Regulation
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Fig 3:
Typical Output Voltage
Deviation Vs Temperature
3
OM185ST
Application Notes:
Stability
The OM185ST Series requires the use of an output capacitor as part of the device frequency compensation.
For all operating conditions, the addition of 150µF aluminum electrolytic or a 22µF solid tantalum on the
output will ensure stability. Normally, capacitors much smaller than this can be used. Many different types
of capacitors with widely varying characteristics are available. These capacitors differ in capacitor tolerance
(sometimes ranging up to
±100%),
equivalent series resistance, and capacitance temperature coefficient.
The 150µF or 22µF values given will ensure stability.
When the adjustment terminal is bypassed to improve the ripple rejection, the requirement for an output
capacitor increases. The values of 22µF tantalum or 150µF aluminum cover all cases of bypassing the
adjustment terminal. Without bypassing the adjustment terminal, smaller capacitors can be used with
equally good results and the table below shows approximately what size capacitors are needed to ensure
stability.
Normally, capacitor values on the order of 100µF are used in the output of many regulators to ensure good
transient response with heavy load current changes. Output capacitance can be increased without limit and
larger values of output capacitor further improve stability and transient response of the regulators.
Recommended Capacitor Values
Input
10µF
10µF
Output
10µF Tantalum, 50µF Aluminum
22µF Tantalum, 150µF Aluminum
Adjustment
None
20µF
Output Voltage - Adjustable Regulators
The OM185ST devices develop a 1.25V reference voltage between the output and the adjust terminal (see
Fig 4). By placing a resistor, R1 between these two terminals, a constant current is caused to flow through
R1 and down through R2 to set the overall output voltage. Normally this current is the specified minimum
load current of 10mA. Because I
ADJ
is very small and constant when compared with the current through R1,
it represents a small error and can usually be ignored.
V
IN
IN
OM185ST
ADJ
OUT
V
OUT
V
ADJ
R
1
I
ADJ
50µA
R
2
R
V
OUT
= V
REF
1+
R
2
+ I
ADJ
R
2
1
Fig 4.
Basic Adjustable Regulator
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OM185ST
Case Outline and Dimensions - TO-257AA 3Pin (T-3)
NOTES:
1. DIMENSIONING & TOLERANCING PER ASME Y14.5M-1994.
2. ALL DIMENSIONS ARE SHOWN IN MILLIMETERS (INCHES).
3. CONTROLLING DIMENSION: INCH.
4. TOLERANCES ARE
±0.010
U.O.S.
5. SEE INDIVIDUAL DATA SHEETS FOR OIN ASSIGNMENTS.
6. OUTLINE USED WITH OM PART NUMBERS ONLY.
PIN ASSIGNMENTS
Pin 1 - ADJUST
Pin 2 - V
OUT
Pin 3 - V
IN
Part Numbering Nomenclature
OM
185
S
T
M
Screening Level
Device Number
Package Code
T = TO-257AA
Isolated / Non-Isolated
S = Isolated
IR WORLD HEADQUARTERS:
233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105
IR LEOMINSTER :
205 Crawford St., Leominster, Massachusetts 01453, USA Tel: (978) 534-5776
Data and specifications subject to change without notice. 06/2008
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