TK70001 Ver la hoja de datos (PDF) - Toko America Inc
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TK70001 Datasheet PDF : 8 Pages
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TK70001
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. The dropout voltage is the difference
between the input voltage and the output voltage. The
measurement current is IOUT = 50 mA. (ICONT = 50 µA,
VIN = 2.5 V).
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.
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
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.
ON/OFF CONTROL CURRENT
The characteristics of TK70001 change by the value of
control current. Please refer to the electrical characteristics
graphs on the data sheet and determine the optimum
value. The standard measurement condition is
ICONT = 50 µA. (The application is max. ICONT = 200 µA). In
the condition where there is very little output current,
connect the resistor RCONT to the control terminal (please
consider the reduction of the terminal voltage, the resistance
value, etc.). This current can be lowered.
THERMAL SENSOR
The thermal sensor protects the device in the event that
the junction temperature exceeds the safe value (Tj =
150 °C). This temperature rise can be caused by external
heat, excessive power dissipation caused by large input to
output voltage drop, or excessive output current. The
switch will shut off when the temperature exceeds the safe
value. As the junction temperature decreases, the switch
will begin to operate again. Under sustained fault conditions,
the switch output will cycle as the device turns off, and then
resets. Damage may occur to the device under extreme
fault conditions.
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-26 is increased to 350 mW. For operation at
ambient temperatures over 25 °C, the power dissipation of
the SOT-26 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
Page 6
January 1999 TOKO, Inc.
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