FA5502P/M
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GND wiring so as not to generate
impedance with other wires.
a common
(13) Prevention of malfunction by negative
voltage of each pin
IDET pin is so designed as to input a negative
voltage. In the case of other pins, however, if large
negative voltage is applied, parasitic elements in IC
may operate and it may cause a malfunction. Pay
attention so that the voltage applied to pins other than
IDET pin will not be lower than -0.3V.
(11-5) VCC pin
A noise applied to VCC pin may cause a malfunction.
To suppress this noise, connect a capacitor near VCC
pin even if IC is energized by another power supply.
Determine the capacitance so that the noise generated
at VCC pin will be within about ±0.6V . Then, make
sure no malfunction occurs by noise.
(12) Voltage rating of IDET pin
The voltage rating of IDET pin, which monitors an
inductor current, is -10V. In case of a general boost
circuit,
a inrush current for charging the output
smoothing capacitor Co flows at the instant when an
AC input voltage is connected. This current may be by
far greater than the input current at a normal operation.
As a result, a voltage much higher than normal may be
applied to IDET pin. Pay attention so that a voltage
beyond the maximum voltage rating of -10V will not be
applied to IDET pin even at an instant when an AC
input voltage has been connected. If there are cases
where a voltage higher than rating is applied to IDET
pin, insert a limiting circuit for inrush current, or add a
Zener diode as shown in Fig.26 or 27 to suppress the
voltage applied to IDET pin.
D
L
Co
Q
ZD
Rs
7
GND
Rn
FA5502
Cn
16
IDET
Fig.26 IDET pin protection (1)
D
L
Co
Q
Rs
ZD
7
GND
Rn
FA5502
Cn
16
IDET
Fig.27 IDET pin protection (2)
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