LM150/LM350A/LM350
3-Amp Adjustable Regulators
General Description
The LM150 series of adjustable 3-terminal positive voltage
regulators is capable of supplying in excess of 3A over a
1.2V to 33V output range. They are exceptionally easy to
use and require only 2 external resistors to set the output
voltage. Further, both line and load regulation are compa-
rable to discrete designs. Also, the LM150 is packaged in
standard transistor packages which are easily mounted and
handled.
In addition to higher performance than fixed regulators, the
LM150 series offers full overload protection available only in
IC's. Included on the chip are current limit, thermal overload
protection and safe area protection. All overload protection
circuitry remains fully functional even if the adjustment termi-
nal is accidentally disconnected.
Normally, no capacitors are needed unless the device is situ-
ated more than 6 inches from the input filter capacitors in
which case an input bypass is needed. An output capacitor
can be added to improve transient response, while bypass-
ing the adjustment pin will increase the regulator's ripple re-
jection.
Besides replacing fixed regulators or discrete designs, the
LM150 is useful in a wide variety of other applications. Since
the regulator is "floating" and sees only the input-to-output
differential voltage, supplies of several hundred volts can be
regulated as long as the maximum input to output differential
is not exceeded, i.e., avoid short-circuiting the output.
By connecting a fixed resistor between the adjustment pin
and output, the LM150 can be used as a precision current
regulator. Supplies with electronic shutdown can be
achieved by clamping the adjustment terminal to ground
which programs the output to 1.2V where most loads draw
little current.
The part numbers in the LM150 series which have a K suffix
are packaged in a standard Steel TO-3 package, while those
with a T suffix are packaged in a TO-220 plastic package.
The LM150 is rated for -55C
T
J
+150C, while the
LM350A is rated for -40C
T
J
+125C, and the LM350 is
rated for 0C
T
J
+125C.
Features
n
Adjustable output down to 1.2V
n
Guaranteed 3A output current
n
Guaranteed thermal regulation
n
Output is short circuit protected
n
Current limit constant with temperature
n
P
+
Product Enhancement tested
n
86 dB ripple rejection
n
Guaranteed 1% output voltage tolerance (LM350A)
n
Guaranteed max. 0.01%/V line regulation (LM350A)
n
Guaranteed max. 0.3% load regulation (LM350A)
Applications
n
Adjustable power supplies
n
Constant current regulators
n
Battery chargers
Connection Diagrams
(TO-3 STEEL)
Metal Can Package
DS009061-4
Case is Output
Bottom View
Order Number LM150K STEEL
or LM350K STEEL
See NS Package Number K02A
Order Number LM150K/883
See NS Package Number K02C
(TO-220)
Plastic Package
DS009061-5
Front View
Order Number LM350AT or LM350T
See NS Package Number T03B
May 1998
LM150/LM350A/LM350
3-Amp
Adjustable
Regulators
1999 National Semiconductor Corporation
DS009061
www.national.com
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
(Note 4)
Power Dissipation
Internally Limited
Input-Output Voltage Differential
+35V
Storage Temperature
-65C to +150C
Lead Temperature
Metal Package (Soldering, 10 sec.)
Plastic Package (Soldering, 4 sec.)
300C
260C
ESD Tolerance
TBD
Operating Temperature Range
LM150
-55C
T
J
+150C
LM350A
-40C
T
J
+125C
LM350
0C
T
J
+125C
Electrical Characteristics
Specifications with standard type face are for T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture Range. Unless otherwise specified, V
IN
- V
OUT
= 5V, and I
OUT
= 10 mA. (Note 2)
Parameter
Conditions
LM150
Units
Min
Typ
Max
Reference Voltage
3V
(V
IN
- V
OUT
)
35V,
1.20
1.25
1.30
V
10 mA
I
OUT
3A, P
30W
Line Regulation
3V
(V
IN
- V
OUT
)
35V (Note 3)
0.005
0.01
%/V
0.02
0.05
%/V
Load Regulation
10 mA
I
OUT
3A (Note 3)
0.1
0.3
%
0.3
1
%
Thermal Regulation
20 ms Pulse
0.002
0.01
%/W
Adjustment Pin Current
50
100
A
Adjustment Pin Current Change
10 mA
I
OUT
3A, 3V
(V
IN
- V
OUT
)
35V
0.2
5
A
Temperature Stability
T
MIN
T
J
T
MAX
1
%
Minimum Load Current
V
IN
- V
OUT
= 35V
3.5
5
mA
Current Limit
V
IN
- V
OUT
10V
3.0
4.5
A
V
IN
- V
OUT
= 30V
0.3
1
A
RMS Output Noise, % of V
OUT
10 Hz
f
10 kHz
0.001
%
Ripple Rejection Ratio
V
OUT
= 10V, f = 120 Hz, C
ADJ
= 0 F
65
dB
V
OUT
= 10V, f = 120 Hz, C
ADJ
= 10 F
66
86
dB
Long-Term Stability
T
J
= 125C, 1000 hrs
0.3
1
%
Thermal Resistance, Junction
K Package
1.2
1.5
C/W
to Case
Thermal Resistance, Junction
K Package
35
C/W
to Ambient (No Heat Sink)
Electrical Characteristics
Specifications with standard type face are for T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture Range. Unless otherwise specified, V
IN
- V
OUT
= 5V, and I
OUT
= 10 mA. (Note 2)
Parameter
Conditions
LM350A
LM350
Units
Min
Typ
Max
Min
Typ
Max
Reference Voltage
I
OUT
= 10 mA, T
J
= 25C
1.238 1.250 1.262
V
3V
(V
IN
- V
OUT
)
35V,
1.225 1.250 1.270
1.20
1.25
1.30
V
10 mA
I
OUT
3A, P
30W
Line Regulation
3V
(V
IN
- V
OUT
)
35V (Note 3)
0.005
0.01
0.005
0.03
%/V
0.02
0.05
0.02
0.07
%/V
Load Regulation
10 mA
I
OUT
3A (Note 3)
0.1
0.3
0.1
0.5
%
0.3
1
0.3
1.5
%
Thermal Regulation
20 ms Pulse
0.002
0.01
0.002
0.03
%/W
Adjustment Pin Current
50
100
50
100
A
Adjustment Pin Current
Change
10 mA
I
OUT
3A, 3V
(V
IN
- V
OUT
)
35V
0.2
5
0.2
5
A
www.national.com
2
Electrical Characteristics
(Continued)
Specifications with standard type face are for T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture Range. Unless otherwise specified, V
IN
- V
OUT
= 5V, and I
OUT
= 10 mA. (Note 2)
Parameter
Conditions
LM350A
LM350
Units
Min
Typ
Max
Min
Typ
Max
Temperature Stability
T
MIN
T
J
T
MAX
1
1
%
Minimum Load Current
V
IN
- V
OUT
= 35V
3.5
10
3.5
10
mA
Current Limit
V
IN
- V
OUT
10V
3.0
4.5
3.0
4.5
A
V
IN
- V
OUT
= 30V
0.3
1
0.25
1
A
RMS Output Noise, % of
V
OUT
10 Hz
f
10 kHz
0.001
0.001
%
Ripple Rejection Ratio
V
OUT
= 10V, f = 120 Hz, C
ADJ
= 0 F
65
65
dB
V
OUT
= 10V, f = 120 Hz, C
ADJ
= 10 F
66
86
66
86
dB
Long-Term Stability
T
J
= 125C, 1000 hrs
0.25
1
0.25
1
%
Thermal Resistance, Junction
K Package
1.2
1.5
C/W
to Case
T Package
3
4
3
4
C/W
Thermal Resistance, Junction
K Package
35
C/W
to Ambient (No Heat Sink)
T Package
50
50
C/W
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is in-
tended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: These specifications are applicable for power dissipations up to 30W for the TO-3 (K) package and 25W for the TO-220 (T) package. Power dissipation is
guaranteed at these values up to 15V input-output differential. Above 15V differential, power dissipation will be limited by internal protection circuitry. All limits (i.e.,
the numbers in the Min. and Max. columns) are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 3: Regulation is measured at a constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating effects are
covered under the specifications for thermal regulation.
Note 4: Refer to RETS150K drawing for military specifications of the LM150K.
Typical Performance Characteristics
Load Regulation
DS009061-33
Current Limit
DS009061-34
Adjustment Current
DS009061-35
Dropout Voltage
DS009061-36
Temperature Stability
DS009061-37
Minimum Operating Current
DS009061-38
www.national.com
3
Typical Performance Characteristics
(Continued)
Ripple Rejection
DS009061-39
Ripple Rejection
DS009061-40
Ripple Rejection
DS009061-41
Output Impedance
DS009061-42
Line Transient Response
DS009061-43
Load Transient Response
DS009061-44
www.national.com
4
Application Hints
In operation, the LM150 develops a nominal 1.25V reference
voltage, V
REF
, between the output and adjustment terminal.
The reference voltage is impressed across program resistor
R1 and, since the voltage is constant, a constant current I
1
then flows through the output set resistor R2, giving an out-
put voltage of
Since the 50 A current from the adjustment terminal repre-
sents an error term, the LM150 was designed to minimize
I
ADJ
and make it very constant with line and load changes.
To do this, all quiescent operating current is returned to the
output establishing a minimum load current requirement. If
there is insufficient load on the output, the output will rise.
EXTERNAL CAPACITORS
An input bypass capacitor is recommended. A 0.1 F disc or
1 F solid tantalum on the input is suitable input bypassing
for almost all applications. The device is more sensitive to
the absence of input bypassing when adjustment or output
capacitors are used but the above values will eliminate the
possibility of problems.
The adjustment terminal can be bypassed to ground on the
LM150 to improve ripple rejection. This bypass capacitor
prevents ripple from being amplified as the output voltage is
increased. With a 10 F bypass capacitor 86 dB ripple rejec-
tion is obtainable at any output level. Increases over 10 F
do not appreciably improve the ripple rejection at frequen-
cies above 120 Hz. If the bypass capacitor is used, it is
sometimes necessary to include protection diodes to prevent
the capacitor from discharging through internal low current
paths and damaging the device.
In general, the best type of capacitors to use is solid tanta-
lum. Solid tantalum capacitors have low impedance even at
high frequencies. Depending upon capacitor construction, it
takes about 25 F in aluminum electrolytic to equal 1 F
solid tantalum at high frequencies. Ceramic capacitors are
also good at high frequencies, but some types have a large
decrease in capacitance at frequencies around 0.5 MHz. For
this reason, 0.01 F disc may seem to work better than a 0.1
F disc as a bypass.
Although the LM150 is stable with no output capacitors, like
any feedback circuit, certain values of external capacitance
can cause excessive ringing. This occurs with values be-
tween 500 pF and 5000 pF. A 1 F solid tantalum (or 25 F
aluminum electrolytic) on the output swamps this effect and
insures stability.
LOAD REGULATION
The LM150 is capable of providing extremely good load
regulation but a few precautions are needed to obtain maxi-
mum performance. The current set resistor connected be-
tween the adjustment terminal and the output terminal (usu-
ally 240
) should be tied directly to the output (case) of the
regulator rather than near the load. This eliminates line
drops from appearing effectively in series with the reference
and degrading regulation. For example, a 15V regulator with
0.05
resistance between the regulator and load will have a
load regulation due to line resistance of 0.05
x I
OUT
. If the
set resistor is connected near the load the effective line re-
sistance will be 0.05
(1 + R2/R1) or in this case, 11.5 times
worse.
Figure 2 shows the effect of resistance between the regula-
tor and 240
set resistor.
With the TO-3 package, it is easy to minimize the resistance
from the case to the set resistor, by using two separate leads
to the case. The ground of R2 can be returned near the
ground of the load to provide remote ground sensing and im-
prove load regulation.
PROTECTION DIODES
When external capacitors are used with
any IC regulator it is
sometimes necessary to add protection diodes to prevent
the capacitors from discharging through low current points
into the regulator. Most 10 F capacitors have low enough
internal series resistance to deliver 20A spikes when
shorted. Although the surge is short, there is enough energy
to damage parts of the IC.
When an output capacitor is connected to a regulator and
the input is shorted, the output capacitor will discharge into
the output of the regulator. The discharge current depends
on the value of the capacitor, the output voltage of the regu-
lator, and the rate of decrease of V
IN
. In the LM150, this dis-
charge path is through a large junction that is able to sustain
25A surge with no problem. This is not true of other types of
positive regulators. For output capacitors of 25 F or less,
there is no need to use diodes.
The bypass capacitor on the adjustment terminal can dis-
charge through a low current junction. Discharge occurs
when
either the input or output is shorted. Internal to the
LM150 is a 50
resistor which limits the peak discharge cur-
rent. No protection is needed for output voltages of 25V or
DS009061-7
FIGURE 1.
DS009061-8
FIGURE 2. Regulator with Line Resistance
in Output Lead
www.national.com
5
PDF 
ZIP