NSC LM345K-5.0 Datasheet
TL/H/7785
LM145/LM345 Negative Three Amp Regulator
January 1995
LM145/LM345 Negative Three Amp Regulator
General Description
The LM145 is a three-terminal negative regulator with a
fixed output voltage of
b
5V and up to 3A load current capability. This device needs only one external componentÐa
compensation capacitor at the output, making it easy to apply. Worst case guarantees on output voltage deviation due
to any combination of line, load or temperature variation
assure satisfactory system operation.
Exceptional effort has been made to make the LM145 immune to overload conditions. The regulator has current limiting which is independent of temperature, combined with
thermal overload protection. Internal current limiting protects against momentary faults while thermal shutdown prevents junction temperatures from exceeding safe limits during prolonged overloads.
Although primarily intended for fixed output voltage applications, the LM145 may be programmed for higher output voltages with a simple resistive divider. The low quiescent drain
current of the device allows this technique to be used with
good regulation.
The LM145 comes in a hermetic TO-3 package rated at
25W. A reduced temperature range part LM345 is also available.
Features
Y
Output voltage accurate to better thang2%
Y
Current limit constant with temperature
Y
Internal thermal shutdown protection
Y
Operates with input-output voltage differential of 2.8V at
full rated load over full temperature range
Y
Regulation guaranteed with 25W power dissipation
Y
3A output current guaranteed
Y
Only one external component needed
Y
PaProduct Enhancement tested
Schematic Diagram
TL/H/7785– 1
C
1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.
Absolute Maximum Ratings
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
(Note 3)
Input Voltage 20V
Input-Output Differential 20V
Power Dissipation Internally Limited
Operating Junction Temperature Range
LM145
b
55§Ctoa150§C
LM345 0
§
Ctoa125§C
Storage Temperature Range
b
65§Ctoa150§C
Lead Temperature (Soldering, 10 sec.) 300
§
C
Electrical Characteristics (Note 1)
Limits
Parameter Conditions LM145 LM345 Units
Min Typ Max Min Typ Max
Output Voltage T
j
e
25§C, I
OUT
e
5 mA,
b
5.1
b
5.0
b
4.9
b
5.2
b
5.0
b
4.8 V
V
IN
eb
7.5
Line Regulation (Note 2) T
j
e
25§C
5 15 5 25 mV
b
20VsV
IN
s
b
7.5V
Load Regulation (Note 2) T
j
e
25§C, V
IN
eb
7.5V
30 75 30 100 mV
5mAsI
OUT
s
3A
Output Voltage
b
20VsV
IN
s
b
7.8V
5mA
s
I
OUT
s
3A
P
s
25W
b
5.20
b
4.80b5.25
b
4.75 V
T
MIN
s
T
j
s
T
MAX
Quiescent Current
b
20VsV
IN
s
b
7.5V
1.0 3.0 1.0 3.0 mA
5mA
s
I
OUT
s
3A
Short Circuit Current V
IN
eb
7.5V, T
j
ea
25§C 4 5.5 4 5.5 A
V
IN
eb
20V, T
j
ea
25§C 2 3.5 2 3.5 A
Output Noise Voltage T
A
e
25§C, C
L
e
4.7 mF
150 150 mV
10 Hz
sfs
100 kHz
Long Term Stability 5 50 5 50 mV
Thermal Resistance
22
§
C/W
Junction to Case
Note 1: Unless otherwise specified, these specifications apply:b55§CsT
j
s
a
150§C for the LM145 and 0§CsT
j
s
a
125§C for the LM345. V
IN
e
7.5V and
I
OUT
e
5 mA. Although power dissipation is internally limited, electrical specifications apply only for power levels up to 25W. For calculations of junction
temperature rise due to power dissipation, use a thermal resistance of 35
§
C/W for the TO-3 with no heat sink. With a heat sink, use 2§C/W for junction to case
thermal resistance.
Note 2: Regulation is measured at constant junction temperature. Changes in output voltage due to heating effects must be taken into account separately. To
ensure constant junction temperature, pulse testing with a low duty cycle is used.
Note 3: Refer to RETS145K-5V for LM145K-5.0 military specifications.
Connection Diagram
Metal Can Package
TL/H/7785– 2
Bottom View
Order Number LM345K-5.0
See NS Package Number K02A
Order Number LM145K-5.0/883 or
SMD
Ý
5962-9064501
See NS Package Number K02C
Typical Applications
Fixed Regulator
TL/H/7785– 3
²
Required for stability. For value given, capacitor must be solid tantalum.
50 mF aluminum electrolytic may be substituted. Values given may be increased without limit.
*Required if regulator is separated from filter capacitor. For value given, ca-
pacitor must be solid tantulum. 50 mF aluminum electrolytic may be substituted.
2
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