TK70003 データシートの表示（PDF） - Toko America Inc
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TK70003 Datasheet PDF : 7 Pages
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TK70003
DEFINITION AND EXPLANATION OF TECHNICAL TERMS
DROPOUT VOLTAGE (VDROP)
The output voltage decreases with the increase of output
current. It is dependent upon the load current and the
junction temperature. It measure the differential voltage
between the input voltage and the output voltage when the
input voltage is set to 2.5 V and the output current is set to
5 mA.
OUTPUT CURRENT (IOUT)
The rated output current is specified under the condition
where the output voltage drops 0.5 V below the no load
value. The input voltage is set to 2.5 V, and the current is
pulsed to minimize temperature effects.
QUIESCENT CURRENT (IQ)
The quiescent current is the current which flows through
the ground terminal under no load conditions (IOUT = 0 mA)
with VIN = 2.5 V and excludes the control pin current.
STANDBY CURRENT (ISTBY)
Standby current is the current which flows into the solid
state switch when the output is turned off by the control
function (VCONT = 0 V). It is measured with VIN = 8 V.
GROUND CURRENT (IGND)
Ground current is the current which flows through the
ground pin(s). It is defined as IIN - IOUT, excluding control
current.
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 (Note: both
VIN pins are connected together and both switches “on” for
this measurement). 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-23-6 is increased to
350 mW. For operation at ambient temperatures over 25
°C, the power dissipation of the SOT-23-6 device should
be derated at 2.8 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:
ON/OFF CONTROL
High is “on” (referenced to ground). The input current is at
the pA level by connecting the control terminal to ground.
REVERSE VOLTAGE PROTECTION
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:
Reverse voltage protection prevents damage due to the
output voltage being higher than the input voltage. This
fault condition can occur when the output capacitor remains
charged and the input is reduced to zero, or when an
external voltage higher than the input voltage is applied to
the output side.
150 °C = 0jA x PD + 25 °C
0jA = 125 °C/ PD
PD is the value when the thermal sensor is activated. A
simple way to determine PD is to calculate VIN x IIN when
the output side is shorted. Input current gradually falls as
temperature rises. You should use the value when thermal
equilibrium is reached.
January 1999 TOKO, Inc.
Page 5
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