Definition of Terms

Dropout Voltage: The input-output voltage differential at

which the circuit ceases to regulate against further reduction

in input voltage. Measured when the output voltage has

dropped 100 mV from the nominal value obtained at 14V in-

put, dropout voltage is dependent upon load current and

junction temperature.

Input Voltage: The DC voltage applied to the input terminals

with respect to ground.

Input-Output Differential: The voltage difference between

the unregulated input voltage and the regulated output volt-

age for which the regulator will operate.

Line Regulation: The change in output voltage for a change

in the input voltage. The measurement is made under condi-

tions of low dissipation or by using pulse techniques such

that the average chip temperature is not significantly af-

fected.

Load Regulation: The change in output voltage for a

change in load current at constant chip temperature.

Long Term Stability: Output voltage stability under acceler-

ated life-test conditions after 1000 hours with maximum

rated voltage and junction temperature.

Output Noise Voltage: The rms AC voltage at the output,

with constant load and no input ripple, measured over a

specified frequency range.

Quiescent Current: The part of the positive input current

that does not contribute to the positive load current. The

regulator ground lead current.

Ripple Rejection: The ratio of the peak-to-peak input ripple

voltage to the peak-to-peak output ripple voltage.

Temperature Stability of V

put voltage for a thermal variation from room temperature to

either temperature extreme.

Application Hints

EXTERNAL CAPACITORS

The LM2925 output capacitor is required for stability. Without

it, the regulator output will oscillate, sometimes by many

volts. Though the 10 µF shown is the minimum recom-

mended value, actual size and type may vary depending

upon the application load and temperature range. Capacitor

effective series resistance (ESR) also effects the IC stability.

Since ESR varies from one brand to the next, some bench

work may be required to determine the minimum capacitor

value to use in production. Worst-case is usually determined

at the minimum junction and ambient temperature and maxi-

mum load expected.

Output capacitors can be increased in size to any desired

value above the minimum. One possible purpose of this

would be to maintain the output voltages during brief condi-

tions of negative input transients that might be characteristic

of a particular system.

Quiescent Current

DS005268-19

Quiescent Current

DS005268-17

Load Transient Response

DS005268-18

Peak Output Current

DS005268-20

Maximum Power

Dissipation (TO-220)

DS005268-21

Output Capacitor ESR

DS005268-22

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