NCP623, NCV8623

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5

DEFINITIONS

Load Regulation − The change in output voltage for a

change in load current at constant chip temperature.

Dropout Voltage − The input/output differential at which

the regulator output no longer maintains regulation against

further reductions in input voltage. Measured when the

output drops 100 mV below its nominal value (which is

measured at 1.0 V differential), dropout voltage is affected

by junction temperature, load current and minimum input

supply requirements.

Output Noise Voltage − The RMS AC voltage at the

output with a constant load and no input ripple, measured

over a specified frequency range.

Maximum Power Dissipation − The maximum total

dissipation for which the regulator will operate within

specifications.

Quiescent Current − Current which is used to operate the

regulator chip and is not delivered to the load.

Line Regulation − The change in input voltage for a

change in the input voltage. The measurement is made under

conditions of low dissipation or by using pulse techniques

such that the average chip temperature is not significantly

affected.

Line Transient Response − Typical over− and

undershoot response when input voltage is excited with a

given slope.

Thermal Protection − Internal thermal shutdown

circuitry is provided to protect the integrated circuit in the

event that the maximum junction temperature is exceeded.

When activated, typically 150

°C, the regulator turns off.

This feature is provided to prevent catastrophic failures from

accidental overheating.

Maximum Package Power Dissipation − The maximum

package power dissipation is the power dissipation level at

which the junction temperature reaches its maximum value

i.e. 125

°C. The junction temperature is rising while the

Depending on ambient temperature, it is possible to

calculate the maximum power dissipation, maximum load

current or maximum input voltage (see Application Hints:

Protection).

The maximum power dissipation supported by the device

is a lot increased when using appropriate application design.

Mounting pad configuration on the PCB, the board material

and also the ambient temperature are affected the rate of

conductivity through PCB, the junction temperature will be

“low” even if the power dissipation is great.

The thermal resistance of the whole circuit can be

evaluated by deliberately activating the thermal shutdown

of the circuit (by increasing the output current or raising the

input voltage for example).

Then you can calculate the power dissipation by

subtracting the output power from the input power. All

variables are then well known: power dissipation, thermal

shutdown temperature (150

°C for NCP623) and ambient

temperature.