LM396 National Semiconductor, LM396 Datasheet - Page 3

• Manufacturer Part Number: LM396
• Description: 10 Amp Adjustable Voltage Regulator
• Manufacturer: National Semiconductor

Power Dissipation (P
(Note 11)
Drop-Out Voltage
LM196 LM396
Electrical Characteristics
Note 1 Unless otherwise stated these specifications apply for T
Note 2 This is a worst-case specification which includes all effects due to input voltage output current temperature and power dissipation Maximum power
(P
Note 3 Line regulation is measured on a short-pulse low-duty-cycle basis to maintain constant junction temperature Changes in output voltage due to thermal
gradients or temperature changes must be taken into account separately See discussion of Line Regulation under Application Hints
Note 4 Load regulation on the 2-pin package is determined primarily by the voltage drop along the output pin Specifications apply for an external Kelvin sense
connnection at a point on the output pin
junction temperature Changes in output voltage due to thermal gradients or temperature changes must be taken into account separately See discussion of Load
Regulation under Application Hints
Note 5 Ripple rejection is measured with the adjustment pin bypassed with 25
bypass capacitor ripple rejection is determined by line regulation and may be calculated from RR
expressed in % V At frequencies below 100 Hz ripple rejection may be limited by thermal effects if load current is above 1A
Note 6 Thermal regulation is defined as the change in output voltage during the time period of 0 2 ms to 20 ms after a change in power dissipation in the regulator
due to either a change in input voltage or output current See graphs and discussion of thermal effects under Application Hints
Note 7 Adjustment pin current change is specified for the worst-case combination of input voltage output current and power dissipation Changes due to
temperature must be taken into account separately See graph of adjustment pin current vs temperature
Note 8 Current limit is measured 10 ms after a short is applied to the output DC measurements may differ slightly due to the rapidly changing junction temperature
tending to drop slightly as temperature increases A minimum available load current of 10A is guaranteed over the full temperature range as long as power
dissipation does not exceed 70W and V
Note 9 Minimum load current of 10 mA is normally satisfied by the resistor divider which sets up output voltage
Note 10 Total thermal resistance junction-to-ambient will include junction-to-case thermal resistance plus interface resistance and heat sink resistance See
discussion of Heat Sinking under Application Hints
Note 11 Although power dissipation is internally limited electrical specifications apply only for power dissipation up to the limits shown Derating with temperature
is a function of both power transistor temperature and control area temperature which are specified differently See discussion of Heat Sinking under Application
Hints For V
Note 12 Dropout voltage is input-output voltage differential measured at a forced reference voltage of 1 15V with a 10A load and is a measurement of the
minimum input output differential at full load
Application Hints
Further improvements in efficiency can be obtained by using
Schottky diodes or high efficiency diodes with lower forward
voltage combined with larger filter capacitors to reduce rip-
ple However this reduces the voltage difference between
input and drive pins and may not allow sufficient voltage to
fully saturate the pass transistor Special transformers are
available from Signal Transformer that have a 1V tap on the
output winding to provide the extra voltage for the drive pin
The transformers are available as standard items for 5V ap-
plications at 5A 10A and 20A Other voltages are available
on special request
Heat Sinking
Because of its extremely high power dissipation capability
the major limitation in the load driving capability of the
LM196 is heat sinking Previous regulators such as LM109
LM340 LM117 etc
which limited power dissipation to about 30W The LM196
MAX
) is specified under Electrical Characteristics
Parameter
IN
b
V
OUT
less than 7V power dissipation is limited by current limit of 10A
MAX
had internal power limiting circuitry
)
7 0V
V
V
I
Full Temperature Range
OUT
IN
IN
IN
b
b
b
s
e
from the bottom of the package Testing is done on a short-pulse-width low-duty-cycle basis to maintain constant
V
V
V
OUT
Conditions
V
OUT
OUT
10A
IN
is less than 7 0V
b
(Note 1) (Continued)
e
e
V
15V
18V
OUT s
j
e
12V
25 C V
IN
b
3
Min
70
50
36
V
F capacitor and is therefore independent of output voltage With no load or
OUT
is guaranteed to dissipate up to 70W continuously as long
as the maximum junction temperature limit is not exceeded
This requires careful attention to all sources of thermal re-
sistance from junction-to-ambient including junction-to-
case resistance case-to-heat sink interface resistance
(0 1 – 1 0 C W) and heat sink resistance itself A good ther-
mal joint compound such as Wakefield type 120 or Thermal-
loy Thermocote must be used when mounting the LM196
especially if an electrical insulator is used to isolate the reg-
ulator from the heat sink Interface resistance without this
compound will be no better than 0 5 C W and probably
much worse With the compound and no insulator interface
resistance will be 0 2 C W or less assuming 0 005 or less
combined flatness run-out of TO-3 and heat sink Proper
torquing of the mounting bolts is important to achieve mini-
mum thermal resistance Four to six inch pounds is recom-
mended Keep in mind that good electrical as well as ther-
mal contact must be made to the case
e
LM196
5V I
Typ
100
2 1
OUT
e
e
10 mA to 10A
Max
2 75
20 log
2 5
10
100 (K
Min
70
50
36
c
V
LM396
OUT
Typ
100
2 1
) where K is line regulation
Max
2 75
2 5
Units
W
W
W
V