AN8022L データシートの表示（PDF） - Panasonic Corporation
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AN8022L Datasheet PDF : 16 Pages
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Voltage Regulators
AN8022L, AN8022SB
s Application Notes (continued)
[1] Main characteristics [Load: CL = 3 300 pF, RL = 20 Ω] (continued)
OVP operating bias current characteristics 1
OVP operating bias current characteristics 2
VCC = 20 V
VCC = 10 V
4.5
2.5
4.0
2.0
3.5
1.5
3.0
1.0
2.5
0.5
-50
-25
0
25
50
75
100
Ambient temperature (°C)
-50
-25
0
25
50
75
100
Ambient temperature (°C)
[2] Operation descriptions
1. Start/stop circuit block
• Start mechanism
When AC voltage is applied and the supply
voltage reaches the start voltage through the cur-
rent from the start resistor, the IC starts opera-
tion. Then the power MOSFET driving starts.
Thereby, bias is generated in the transformer
and the supply voltage is given from the bias
coil to the IC. (This is point a in figure 1.)
During the period from the time when the
start voltage is reached and the voltage is gen-
erated in the bias coil to the time when the IC is
provided with a sufficient supply voltage, the
supply voltage of the IC is supplied by the ca-
pacitor (C1) connected to VCC.
Since the supply voltage continuously de-
creases during the above period (area b in figure
1), the power supply is not able to start (state c
in figure 1), if the stop voltage of the IC is
reached before the sufficient supply voltage is
supplied from the bias coil.
After AC rectification
Start resistance
R1
VCC
VOUT
C1
GND
Before start
Start voltage
a
Stop voltage
b
Figure 1
Start
Voltage supplied
from bias coil
Start condition
c Start failure
• Function
The start/stop circuit block is provided with the function to monitor the VCC voltage, and to start the operation
of IC when VCC voltage reaches the start voltage (14.2 V typical), and to stop when it decreases under the stop
voltage (9.2 V typical). A large voltage difference is set between start and stop (5.0 V typical), so that it is easier
to select the start resistor and the capacitor to be connected to VCC .
Note) To start up the IC operation, the startup current which is a pre-start current plus a circuit drive current is necessary.
Set the resistance value so as to supply a startup current of 450 µA.
7
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