Parameter

Conditions

LM196

LM396

Units

Min

Typ

Max

Min

Typ

Max

70

100

70

100

W

(Note 11)

50

50

W

36

36

W

Drop-Out Voltage

21

25

21

25

V

LM196LM396

Full Temperature Range

275

275

Note 1

Note 2

This is a worst-case specification which includes all effects due to input voltage output current temperature and power dissipation Maximum power

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

from the bottom of the package Testing is done on a short-pulse-width 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 Load

Regulation under Application Hints

Note 5

Ripple rejection is measured with the adjustment pin bypassed with 25 mF capacitor and is therefore independent of output voltage With no load or

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 02 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

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

Note 12

Dropout voltage is input-output voltage differential measured at a forced reference voltage of 115V with a 10A load and is a measurement of the

minimum inputoutput 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

had internal power limiting circuitry

which limited power dissipation to about 30W The LM196

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

(01 – 10 CW) 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 05 CW and probably

much worse With the compound and no insulator interface

resistance will be 02 CW or less assuming 0005 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

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