1.5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)

LM1086

THERMAL CONSIDERATIONS

The LM1086 series have internal power and thermal limiting circuitry designed to protect the device

under overload cinditions. However maximum junction temperature ratings should not be exceeded

under continous normal load conditions.

Careful consideration must be given to all sourses of thermal resistance from junction to ambient,

including junction-to- ase, case-to-heat sink interface and heat sink resistance itself. To ensure

safe operating temperatures and reflect more accurately the device temperature, new thermal

resistance specifications have been developed. Unlike order reguators with a single junction-to-

case thermal resistance speccification, the data section for these new regulators provides a

separate thermal resistance and maximum juntion temperature for both the Control Section and the

Power Transistor. Calculations for both temperatures under certain conditions of ambient

temperature and heat sink resistance and to ensure that both thermal limits are met.

Junction-to-case thermal resistance is specified from the IC junction to the bottom of the case

directly below the die. This is the lowest resistance path for the heat flow. In order to ensure the

best possible thermal flow from this area of the package to the heat sink proper mounting is

required. Thermal compound at the case-to-heat sink interface is recommended. A thermarlly

conductive spacer can be used, if the case of the device must be electrically isolated, but its

added contribution to thermal resistance has to be considered.

HTC

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