TOKO Inc.
IC Data Sheet
TK112xxC
GC3-H026
GC3-H026B
B
BPage
Page
Page 17
Application hint
On/Off Control
It is recommended to turn the regulator Off when the
circuit following the regulator is non-operating. A design
with little electric power loss can be implemented. We
recommend the use of the on/off control of the regulator
without using a high side switch to provide an output from
the regulator. A highly accurate output voltage with low
voltage drop is obtained.
Because the control current is small, it is possible to control it directly by CMOS logic.
The PULLDOWN resistance (500K
) is built into the control terminal.
The noise and the ripple rejection characteristics depend on the capacitance on the Vref terminal.
The ripple rejection characteristic of the low frequency region improves by increasing the
capacitance of Cnp.
A standard value is Cnp=0.068
F. Increase Cnp in a design with important output noise and ripple
rejection requirements. The IC will not be damaged if the capacitor value is increased.
The on/off switching speed changes depending on the Np terminal capacitance. The switching speed
slows when the capacitance is large.
Parallel
Parallel connected
connected
connected ON/OFF
ON/OFF
ON/OFF Control
Control
Current boost
For current boost applications, use the products below. A low voltage drop, high current regulator
can be easily made.
TK714xx
Only the PNP transistor for the current boost is external.
TK732xx
( For Iout=10A Max regulator)
Built-in Short circuit protection: a constant current can be set by an external
resistor.
The figure at the left illustrates multiple regulators being
controlled by a single On/Off control signal. There is a
possibility of overheating because the power loss of the low
voltage side IC (TK11220C) is large. The series resistor
(R) is put in the input line of the low output voltage
regulator in order to prevent over-dissipation. The voltage
dropped across the resistor reduces the large input-to-
output voltage across the regulator, reducing the power
dissipation in the device. When the thermal sensor works,
a decrease of the output voltage, oscillation, etc.
may
be observed.
2.0V
5V
3.3V
On/Off Cont.
Vin
TK11250C
TK11233C
TK11220C
R
REG
Vsat
On/Off Cont.