LP2978 datasheet(4/7 Pages) NSC

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Electrical Characteristics (Continued)

Note 3: The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junction-to-ambient thermal resistance, θJ-A, and

the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperture is calculated using:

Where the value of

θJ-A for the SOT-23 package is 220˚C/W in a typical PC board mounting. Exceeding the maximum allowable dissipation will cause excessive die

temperature, and the regulator will go into thermal shutdown.

Note 4: If used in a dual-supply system where the regulator load is returned to a negative supply, the LP2978 output must be diode-clamped to ground.

Note 5: The output PNP structure contains a diode between the VIN to VOUT terminals that is normally reverse-biased. Reversing the polarity from VIN to VOUT will

turn on this diode.

Note 6: Limits are 100% production tested at 25˚C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control

(SQC) methods. The limits are used to calculate National’s Average Outgoing Quality Level (AOQL).

Note 7: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below the value measured with a 1V differential.

Note 8: The ON/OFF input must be properly driven to prevent possible misoperation. For details, refer to Application Hints.

LP2978 Datasheet(PDF) 4 Page - National Semiconductor (TI)

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