upc1909 Renesas Electronics Corporation., upc1909 Datasheet - Page 20

• Manufacturer Part Number: upc1909
• Description: Switching Regulator Control Ic
• Manufacturer: Renesas Electronics Corporation.

20
simultaneously when V
inadvertently turned on. To prevent this, speed up the rising of V
that the standby current (I
circuit will be cut-off, which weakens the drive capacity of the OUT
If this drive capacity is weakened, the charge that has accumulated at the power MOS FET gates may not be sufficiently
discharged, blunting the falling section of the power MOS FET gate drive waveform. In this case, connecting a capacitor
of at least 0.47 F between the V
charge accumulated at the gates of the power MOS FET.
while operation is stopped until V
V
causing the oscillation frequency to drop.
the levels of the triangle wave (C
dividing the resistance of V
oscillation frequency drops, standard applications are not affected. Further study will be required, however, including for
transient states.
Note that when the rising of V
The pull-up resistance value (R) can be calculated from the following equation.
For the same reason, if V
Because the operation start and stop voltages in the PC1909 are 9 V TYP. and 5 V TYP. respectively, V
In standard applications, V
CC
, as can be seen in Figure 4-3. When V
R [k ] =
Remark V
V
CC(MAX.)
CC(MAX.)
0.1 [mA]
REF
CC(SB)
: The highest power supply voltage that can be applied at startup without causing malfunction.
CC
is in a range of about 0.45 to 0.5 V, which may result in the external power MOS FET being
[V]
REF
REF
drops below the operation stopped voltage (V
, if V
) will increase by only the current that flows through the connected resistor.
is resistance-divided to create the DTC
0.5
REF
REF
CC
T
REF
6
5
4
3
2
1
0
) and internally level-shifted triangle wave (dC
pin and GND allows sufficient time and output block drive capacity to discharge the
is 5 V or lower. However, when V
is later than the rising of V
drops, each of the above will drop in proportion to V
Figure 4-3. V
1
Data Sheet G14309EJ2V0DS00
REF
2
falls, the constant current value of the triangle wave oscillator decreases,
V
3
CC
- Supply Voltage - V
REF
I
REF
4
vs. V
= 0 A
5
I
CC
REF
6
REF
Characteristics
= 10 mA
V
7
1
H
CC
by pulling it up to V
and OUT
T
A
8
at startup, OUT
CC
= 25 C
1
, DTC
reaches about 6.5 V, V
9
CC(L to H)
2
10
outputs when the power supply is cut-off.
2
, and FB voltages. In addition, because
V
CC(L to H)
– V
T
) are also generated internally by
CC
H
1
), V
and OUT
with a resistor. Note, however,
REF
REF
and the constant current
. As a result, even if the
REF
2
become high level
falls together with
PC1909
REF
is output