FA7703 Datasheet, PDF (20/21 Pages) Fuji Electric – FUJI Power Supply Control IC

FA7703/04
FA7703/7704
(12)To protect FA7703/04 from application of
negative voltage
If rather large negative voltage is applied to any
terminal of FA7703/04, then internal parasitic
elements start operating, and they may cause
malfunctions. Accordingly, the negative voltage,
which is applied to each terminal of the ICs,
must be kept above -0.3V.
In the case of OUT terminal, in particular, the
oscillation of voltage occurring after MOSFET’s
turning off can be applied to OUT terminal
through MOSFET’s parasitic capacitance. As a
result, there is a possibility that the negative
voltage is applied to OUT terminal. If this
negative voltage reaches -0.3V or below,
connect an Schottky barrier diode between OUT
terminal and GND terminal as shown in Fig. 14.
The Schottky barrier diode’s forward direction
voltage clamps the voltage applied to OUT
terminal. In this case, use the Schottky barrier
diode with low voltage drop in forward direction.
Other terminals should be kept above -0.3 V
also based on the same reasons.
9
Vcc
OUT1
2
10 8
GND
7
SBD
Fig.14
(13)Forbidden use of external forcible
latched operation for CS terminal
If the external voltage of 2.0V or more is
forcibly applied to CS terminal in normal
operation (clamped at 1.2V), the IC may be
seriously damaged because the clamp circuit is
not equipped with any resistor for limiter.
Therefore, DO NOT apply external high voltage
to CS terminal.
Fuji Electric Systems Co., Ltd.
AN-057E Rev.1.0
Jun-2010
20
http://www.fujielectric.co.jp/fdt/scd/