FA5604 Datasheet, PDF (19/31 Pages) Fuji Electric – FUJI Power Supply Control IC

FA5604/5605/5606
(iii)External latch function
When the CS pin voltage exceeds 7.3V (50sec), the IC is stopped the switching. If the VCC voltage reduced to
9.7V (typ.) (ON threshold voltage of UVLO) or less, the latch hold mode can be released.
After the latch hold mode, the CS pin voltage becomes 7.3V or less is maintained to this mode. However, it is
necessary to keep supplying the consumption current 190A (VCC=14V) from input Vin through the startup
resistor.
When the current supplied from Vin is less than the consumption current of IC, VCC reduced to the UVLO voltage
and the latch hold mode cannot be maintained.
During normal operation, the CS pin voltage is clamped at 3.8V by internal zener diode. The VF pin is input to the
voltage proportional to the output voltage
In normal operation, the CS pin voltage is clamped at 3.8V by internal zener diode with maximum sink current
100A (max.). Therefore, to raise the CS pin voltage to 7.3V or more, 200A or a higher current needs to be
supplied from the optocoupler. Set the current input to the CS pin to 2 mA or less.
(iv)ON/OFF function
The IC can be turned ON/OFF control via an external signal applied to the CS pin. Fig.11 shows the ON/OFF
control circuit, and Fig.12 is a timing chart.
The IC is turned off when the CS pin voltage is externally made to drop below 0.60V. The output enters Low
voltage state. Required IC current consumption during shutdown is 185A (Vcc=10.5V), and this current must be
supplied through the start up resistor. If the supplied current from Vin is lower than the current consumption, Vcc is
reduced to the UVLO voltage and the turned off state for CS pin cannot be maintained.
In case of turning on operation, open the CS pin and the CS pin voltage exceeds 1.0V. So the power supply
begins operation with soft-start.
VF ⁷
FB 2
ON/OFF
Ccs
▽ ▽ _CS
8
OCP
timer
0.75 / 0.60V
ON/OFF
VCC
6
OCP
Latch
▽
10uA
7.3V ^▽
3.8V
▽
PWM
OUT
OSC
1
RT
Fig.11
CS pin voltage ^(3.8V)
FB pin voltage
OSC output
ON/OFF comparator
(0.75/0.60V)
H
OUT pin voltage ^L
ON Mode OFF Mode
Fig.12
Fuji Electric Co., Ltd.
AN-033E Rev.1.2
April-2011
19
http://www.fujielectric.co.jp/products/semiconductor/