STMicroelectronics LM138, LM238, LM338 Technical data
ADJUSTABLE VOLTAGE REGULATO RS
■ GUARANTEED 7A PEAK OUTPUT
CURRENT
■ GUARANTEED 5A OUT PU T CURRENT
■ ADJUSTABLE OUTPUT DOWN TO 1.2V
■ LINE REGULATION TYPICALLY 0.005%/V
■ LOAD REGULATION TYPICALLY 0.1%
■ GUARANTEED THERMAL REGULATION
■ CURRENT LIMIT CONSTANT WITH
TEMPERATURE
■ STANDARD 3-LEAD TRANSISTOR
PACKAGE
DESCRIPTION
The LM138/LM238/LM 338 are adjustable
3-terminal positive voltage regulators capable of
supplying in excess of 5A over a 1.2V to 32V
output range. They are exceptionally eas y to use
and requ ire only 2 resistors to set the output
voltage. Careful circuit design has resulted i n
outstanding load and line r egulation comparable
to many commercial power supplies. The LM138
family is supplied in a standard 3-lead transistor
package.
A unique feature of the LM138 family is
time-de-pendent current limiting. Th e current limit
circuitry allows peak c urrent s of up to 12A to be
drawn from the regulator for sh ort periods of time.
LM138/LM238
LM338
THREE-TERMINAL 5 A
TO-3
This allows the LM138 to be us ed with heavy
transient loads and speeds start-up underfull-load
conditions. Under sustained loading conditions,
the current limit decreases to a safe value
protecting the regulator. Also included on the chip
are thermal overload prot ec tion and safe area
protection f or the power transistor. Overlo ad
protection remains functional even if the
adjustment pin is accidentally disconnec ted.
Normally, no capacitors are needed unless the
device is s it uated far from the input filter
capacitors in which case an input bypass is
needed. An optional output capacitor can be
added to improve transient respons e. The
adjustment terminal can be bypassed to
achieve.very high ripple rejection ratios which are
SCHEMATIC DIAGRAM
1/14April 2003
LM138-LM238-LM338
difficult to achiev e with standard 3-terminal
regulators.
Besides replacing fixed regulators or disc rete
designs, the LM238 is useful in a wide variety of
other applications. Since the regulator i s "floating"
and sees only the input-to-outpu t differential
voltage, supplies of several hundred volts can be
regulated as long as the maximum input to input
differential is not exceeded.
The LM138/LM238/LM338 are packaged in
standard ste el TO-3 transistor packages. The
LM138 is rated for operation from -55°C to 150°C,
the LM 238 from –25°C to 150°C and the LM338
from 0°C to 125°C.
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
V
I-VO
P
T
T
lead
T
oper
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is
not implied.
Input Output Voltage Differential
Power Dissipation
tot
Storage Temperature Range
stg
Lead Temperature (Soldering, 10 seconds)
Operating Junction Temperature Range LM138 -55 to 150
LM338 0 to 125
35 V
Internally Limited
-65 to 150 °C
300 °C
°CLM238 -25 to 125
THERMAL DATA
Symbol Parameter Value Unit
R
thj-case
R
thj-amb
Thermal Resistance Junction-case
Thermal Resistance Junction-ambient
1.4 °C/W
35 °C/W
CONNECTION DIAGRAM (top view)
ORDERING CODES
TYPE TO-3 TEMPERATURE RANGE
LM138 LM138K -55°C to 150°C
LM238 LM238K -25°C to 150°C
LM338 LM338K 0°C to 125°C
TO-3
2/14
LM138-LM238-LM338
ELECTRICAL CHARACTERISTICS OF LM138/LM238 (TJ= -55 to 150° C for LM138,
T
= -25 to 150°C for LM238, VI-VO=5V,IO= 2.5 A . Although power dissipation is internally limited, these
J
specifications apply to power dissipat ion up to 50W, unless otherwise specified).
Symbol Parameter Test Conditions Min. Typ. Max. Unit
Line Regulation (Note 1) Ta= 25°C, VI-VO= 3 to 35 V 0.005 0.01 %/V
K
VI
Load Regulation (Note 1) Ta= 25°C
K
VO
I
=10mAto5A
O
Thermal Regulation Pulse = 20 ms 0.002 0.01 %/W
I
Adjustment Pin Current 45 100 µA
adj
∆I
Adjustment Pin Current
adj
Change
Reference Voltage VI-VO= 3 to 35 V, IO=10mAto5A
V
ref
IL=10mAto5A VI-VO= 3 to 35 V 0.2 5 µA
P≤50 W
Line Regulation (Note 1) VI-VO= 3 to 35 V 0.02 0.04 %/V
K
VI
Load Regulation (Note 1) IO=10mAto5A VO≤5 V 20 30 mV
K
VO
K
Temperature Stability TJ=T
VT
I
O(min)
I
O(max)
V
Note 1: Regulation is measured at constant junction temperature. Changes in output voltage due to heating effects are taken into account
separately by thermal rejection.
Minimum Load Current VI-VO≤35 V 3.5 5 mA
Current Limit VI-VO≤10 V DC 5 8 A
RMS Output Noise
NO
(% of V
Ripple Rejection Ratio VO=10V,f=120Hz 60 dB
R
vf
Long Term Stability Ta= 125°C 0.3 1 %
K
VH
)
O
T
C
a
adj
to T
min
max
= 25°C f = 10 Hz to 10 KHz 0.003 %
=10µF 60 75
≤5V 5 15 mV
V
O
≥5 V 0.1 0.3 %
V
O
1.19 1.24 1.29 V
≥ 5 V 0.3 0.6 %
V
O
1%
0.5 ms Peak 7 12
V
=30V 1
I-VO
3/14
LM138-LM238-LM338
ELECTRICAL CHARACTERISTICS OF LM338 (TJ= 0 to 150°C, VI-VO=5V,IO=2.5A.
Although power dissipation is internally limited, these specifications appl y to power dissipation up to 50W,
unless otherwise spec ified).
Symbol Parameter Test Conditions Min. Typ. Max. Unit
Line Regulation (Note 1) Ta= 25°C, VI-VO= 3 to 35 V 0.005 0.03 %/V
K
VI
Load Regulation (Note 1) Ta= 25°C
K
VO
I
=10mAto5A
O
Thermal Regulation Pulse = 20 ms 0.002 0.02 %/W
I
Adjustment Pin Current 45 100 µA
adj
∆I
Adjustment Pin Current
adj
Change
Reference Voltage VI-VO= 3 to 35 V, IO=10mAto5A
V
ref
IL=10mAto5A VI-VO= 3 to 35 V 0.2 5 µA
P≤50 W
Line Regulation (Note 1) VI-VO= 3 to 35 V 0.02 0.06 %/V
K
VI
Load Regulation (Note 1) IO=10mAto5A VO≤5 V 20 50 mV
K
VO
K
Temperature Stability TJ=T
VT
I
O(min)
I
O(max)
V
Note 1: Regulation is measured at constant junction temperature. Changes in output voltage due to heating effects are taken into account
separately by thermal rejection.
Minimum Load Current VI-VO≤35 V 3.5 10 mA
Current Limit VI-VO≤10 V DC 5 8 A
RMS Output Noise
NO
(% of V
Ripple Rejection Ratio VO=10V,f=120Hz 60 dB
R
vf
Long Term Stability Ta= 125°C 0.3 1 %
K
VH
)
O
T
C
a
adj
to T
min
max
= 25°C f = 10 Hz to 10 KHz 0.003 %
=10µF 60 75
≤5V 5 25 mV
V
O
≥5 V 0.1 0.5 %
V
O
1.19 1.24 1.29 V
≥ 5 V 0.3 1 %
V
O
1%
0.5 ms Peak 7 12
V
=30V 1
I-VO
Figure1 : Current Limit Figure2 : Current Limit
4/14
LM138-LM238-LM338
Figure3 : Current Limit
Figure4 : Load Regulation
Figure6 : A djustment Current
Figure7 : Temperature Stability
Figure5 : Dropout Voltage
Figure8 : Output Impedance
5/14
Loading...