FA5527 FUJI [Fuji Electric], FA5527 Datasheet - Page 21

• Manufacturer Part Number: FA5527
• Description: Fuji Switching Power Control IC
• Manufacturer: FUJI [Fuji Electric]

(10) Over-Voltage Protection of FA5526/27/28
protection circuits to monitor Vcc voltage. Fig.16 shows
its block diagram and Fig.17 its timing chart.
(OVP) reference voltage, 28V, an internal 1.3mA constant
current source is tuned on.
the CS pin at 4V is 55uA, CS pin voltage quickly
increases when the 1mA constant current source is turned
on. When CS voltage exceeds comparator (Latch)
reference voltage, 8.5V, the IC changes to the latch mode.
detection to the latch mode, is given as follows.
“Reg” circuit, is turned off and OUT pin voltage is held to
be low., and the current form the CS pin changes to 5µA.
voltage due to cutting off of input voltage or through
forcibly decreasing CS pin voltage to 7.4V or less.
Moreover, pay attention to the relationship between wiring
at the VH pin and reset time in the latch mode.
（See “9-(1) Start-up circuit.”）
(11) Over-Voltage Protection of FA5536/37/38
protection ( OVP ) circuits to monitor Vcc voltage similar
to FA5526/27/28.
mode.
additional external circuit is necessary as mentioned on
page 28 to 29 ( See “10-(4)” ).
(12) Under-Voltage Lock-Out circuit
prevent malfunction when Vcc voltage drops. When Vcc
voltage increases from 0V, the IC starts operation at Vcc =
15V (typ.). As the supply voltage decreases, the IC stops
operation at Vcc = 9V(typ.).
the IC stops operation, OUT pin and CS pin voltage are
forced to be low, resetting soft start, and overload and
overvoltage timer latch protection.
AN-087E Rev.1.0
April-2011
FA5526, FA5527 and FA5528 have built-in over-voltage
When VCC voltage increases and exceeds comparator
Since sink capability of the zener diode which clamps
The delay time td
In the latch mode, an internal power supply source, 5V
The latch mode can be reset through decreasing Vcc
FA5536, FA5537 and FA5538 have built-in over-voltage
However, the OVP of FA5536/37/38 is Auto-Recovery
Therefore, when you need the OVP as latch mode, the
The IC has a built-in undervoltage lockout circuit to
When the undervoltage lockout circuits operates and
td
Here, Cs is a capacitance connected to CS pin [ uF ].
Fuji Electric Co., Ltd.
(OVP)
[ ms ] = 2.85 * Cs [ uF ] ( typical value )
(OVP),
the time from over-voltage
FA5526/5527/5528/5536/5537/5538
21
FB
Fig.17 Over-Voltage protection timing chart
2
Fig.16 Over Voltage protection circuit
5V Reg.
( only for FA5526 / 5527 / 5528 )
5V
5V Reg.
UVLO
2.8V
( only for FA5526 / 5527 / 5528 )
VCC
ENB
Overload
http://www.fujielectric.co.jp/products/semiconductor/
Latch
UVLO
4.8V
8.5V/7.7V
S
R
Cs
F.F.
Q
1
CS
OVP
1.3mA
ENB
28V
6
5
VCC
OUT