TK65833STL データシートの表示（PDF） - Toko America Inc

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TK65833STL

CMOS LDO REGULATOR WITH HIGH ACTIVE CONTROL

Toko America Inc  

ADVANCED INFORMATION

DEFINITION AND EXPLANATION OF TECHNICAL TERMS

OUTPUT VOLTAGE (VOUT)

The output voltage is specified with VIN = (VOUT(TYP) + 1 V)

and IOUT = 1 mA.

DROPOUT VOLTAGE (VDROP)

The dropout voltage is the difference between the input

voltage and the output voltage at which point the regulator

starts to fall out of regulation. Below this value, the output

voltage will fall as the input voltage is reduced. It is

dependent upon the load current and the junction

temperature.

OUTPUT CURRENT (IOUT)

Normal operating output current. This is limited by package

power dissipation.

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 VIN = VOUT + 0.5 V to VIN = 8 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 VIN = VOUT +1 V. The load

regulation is specified under output current step conditions

of 1 mA to 50 mA.

QUIESCENT CURRENT (IQ)

The quiescent current is the current which flows through

the ground terminal under no load conditions (IOUT = 0 mA).

STANDBY CURRENT (ISTBY)

Standby current is the current which flows into the regulator

when the output is turned off by the control function

(VCONT = 0 V). It is measured with VIN = 8 V.

SENSOR CIRCUITS

Overcurrent Sensor

The overcurrent sensor protects the device if the output is

shorted to ground.

PACKAGE POWER DISSIPATION (PD)

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 (VIN x IIN)

and the output power (VOUT x IOUT) increases. The rate of

temperature rise 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 mounted on

the recommended mounting pad, the power dissipation of

the SOT-23-5 is increased to 500 mW. For operation at

ambient temperatures over 25 °C, the power dissipation of

the SOT-23-5 device should be derated at 4.0 mW/ °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. These

measurements should allow for the ambient temperature

of the PCB. The value obtained from PD /(150 °C - TA) is the

derating factor. The PCB 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:

Tj = 0jA x PD + TA

For Toko ICs, the internal limit for junction temperature is

150 °C. If the ambient temperature (TA) is 25 °C, then:

150 °C = 0jA x PD + 25 °C

0jA = 125 °C / PD

February 1999 TOKO, Inc.

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