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December 1998 TOKO, Inc.

TK116xxU

PACKAGE POWER DISSIPATION (P

This is the power dissipation level at which the thermal

sensor is activated. The IC contains an internal thermal

sensor which monitors the junction temperature. When

the junction temperature exceeds the monitor threshold of

150

°C, the IC is shut down. The junction temperature

rises as the difference between the input power (V

and the output power (V

temperature is greatly affected by the mounting pad

configuration on the PCB, the board material and the

ambient temperature. When the IC mounting has good

thermal conductivity, the junction temperature will be low,

even if the power dissipation is great. When the radiation

of heat is good, the device temperature will be low, even if

the power loss is great. When mounted on the

recommended mounting pad, the power dissipation of the

SOT-89 package is 1000 mW. Derate the power dissipation

at 8 mW/

°C for operation above 25 °C. To determine the

power dissipation for shutdown when mounted, attach the

device on the actual PCB and deliberately increase the

output current (or raise the input voltage) until the thermal

protection circuit is activated. Calculate the power

dissipation of the device by subtracting the output power

from the input power. The measurements should allow for

the ambient temperature of the PCB. The value obtained

from P

mounting pad should provide maximum thermal

conductivity in order to maintain low device temperatures.

As a general rule, the lower the temperature, the better the

reliability of the device. The thermal resistance when

mounted is expressed as follows:

T

For Toko ICs, the internal limit for junction temperature is

150

°C. If the ambient temperature (T

150

°C = Θ

Θ

P

simple way to determine P

the output side is shorted. Input current gradually falls as

temperature rises. You should use the value when the

DEFINITION AND EXPLANATION OF TECHNICAL TERMS

LINE REGULATION (Line Reg)

Line regulation is the ability of the regulator to maintain a

constant output voltage as the input voltage changes. The

line regulation is specified as the input voltage is changed

from V

LOAD REGULATION (Load Reg)

Load regulation is the ability of the regulator to maintain a

constant output voltage as the load current changes. It is

a pulsed measurement to minimize temperature effects

with the input voltage set to V

regulation is specified under three output current step

conditions of 0 mA to 30 mA, 0 mA to 100 mA and 0 mA to

150 mA.

DROPOUT VOLTAGE (V

This is a measure of how well the regulator performs as the

input voltage decreases. The smaller the number, the

further the input voltage can decrease before regulation

problems occur. Nominal output voltage is first measured

when V

the output voltage has dropped 100 mV from the nominal,

V

by load current and junction temperature.

GROUND CURRENT (I

Ground current is the current which flows through the

ground pin(s). It is defined as I

current.

OUTPUT NOISE VOLTAGE

This is the effective AC voltage that occurs on the output

voltage under the condition where the input noise is low

and with a given load, filter capacitor, and frequency

range.

THERMAL PROTECTION

This is an internal feature which turns the regulator off

when the junction temperature rises above 150

°C. After

the regulator turns off, the temperature drops and the

regulator output turns back on. Under certain conditions,

the output waveform may appear to be an oscillation as the

output turns off and on and back again in succession.