tk64829amf Toko Inc., tk64829amf Datasheet - Page 28

• Manufacturer Part Number: tk64829amf
• Description: Auto Discharge Function, Ultra Small Package, High Rr, Fast Response, Low Noise, 300ma Cmos Ldo Regulator Ic Tk648xxamf
• Manufacturer: Toko Inc.

P
when the output side is shorted. Input current gradually
falls as output voltage rises after working thermal
shutdown. You should use the value when thermal
equilibrium is reached.
5. Read off the value of P
6. DP
A simple way to determine P
1. Find P
2. Plot P
3. Connect P
4. In design, take a vertical line from the maximum
The maximum output current at the highest operating
temperature will be I
Please use the device at low temperature with better
radiation. The lower temperature provides better quality.
D
is easily calculated.
circuited).
with a straight line.
operating temperature (e.g., 75°C) to the derating
curve.
vertical line intersects the derating curve. This is taken
as the maximum power dissipation DPd.
DP
P
P
D
D
D
D
÷ (V
(mW)
D
against 25°C.
Procedure (When mounted on PCB.)
D
In,MAX
Fig12-6: How to determine DP
D
(V
25
to the point corresponding to the 150°C
In
2
−V
×I
5
In
Out
Out
50
when the output side is short-
)=I
≅ DP
D
Out
75
T
against the point at which the
D
a
(at 75°C)
4
(°C)
÷ (V
D
100
is to calculate V
In,MAX
3
125
-V
D
Out
).
150
In
×I
GC3-O005
In
12-3. On/Off Control
circuit following the regulator is not 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.
Parallel Connected On/Off Control
by a single On/Off control signal. There is concern of
overheating, because the power loss of the low voltage
side IC (TK64812A) 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.
V
It is recommended to turn the regulator Off when the
The above figure is multiple regulators being controlled
In
Control Terminal Voltage ((V
Fig12-8: The example of parallel connected IC
On/Off
Cont.
Fig12-7: The use of On/Off control
V
V
REG
Cont
Cont
> 1.2V
< 0.2V
TK64842A
TK64828A
TK64812A
On/Off Cont.
Vsat
Cont
)
TK648xxAMF
On/Off State
Off
On
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V
4.2V
2.8V
1.2V
Out