AN8032
s
Application Notes (continued)
[2] Operation descriptions (continued)
1. Normal control (continued)
3) Description of each function (continued)
(1)
V
B
(continued)
Voltage Regulators
I
D
SDB
V
B
lower limit
voltage clamp
current
V
B
upper limit
voltage clamp
current
I
DS
I
D
Time
V
CC
AN8032
Lower limit
voltage clamp
V
B
V
B
Clamp upper
limit voltage
I
DS
V
B
V
B
threshold value
Upper limit
voltage clamp
Time
Clamp upper
limit voltage
Reset operation
of inductor
GND
Figure 5. Explanation of V
B
operation
<Setting the V
B
terminal constant>
•
Regulation by clamper in/out-current value
The allowable output current of the upper
limit voltage clamper is
−5
mA and the allow-
able input current of the lower limit voltage
clamper is
+5
mA. Either one of these allow-
able values is exceeded, the voltage clamp op-
eration of the V
B
terminal is not guaranteed.
Therefore, R
B
should be set so that these values
are not exceeded.
•
Consumption current and delay
When the R
B
value is too large, the V
B
threshold could be exceeded. When the R
B
value
is too small, the consumption current becomes
too large.
In order to determine the R
B
value prop-
erly, the input voltage range and the dispersion
of components should be taken into consider-
ation and it should be confirmed that a stable
operation can be ensured under start/overload
conditions or under a small load condition.
±5
mA or less
AN8032
V
B
R
B
R
B
too large
:
Consumption current becomes small, however,
T
OFF
is extended by the delay amount because of low speed.
R
B
too small
:
Speed is high, however, consumption current
is small and undershoot tends to be generated easily.
10
PANASONIC [ PANASONIC SEMICONDUCTOR ]
