SRP Hitachi Semiconductor, SRP Datasheet - Page 27

• Manufacturer Part Number: SRP
• Description: High Speed Current Mode PWM Control IC for Switching Power Supply
• Manufacturer: Hitachi Semiconductor

2. OVP latch output overvoltage protection (the HA17384H and HA17385H only)
The OVP latch is incorporated in the error amp input pin (FB). If the FB pin is pulled up to 7.0 V typ.
just once when the power supply enters any kind of error state, IC operation can be halted and held as it
is (latched). To reset the latch, drop the IC’s supply voltage to 7.0 V typ. or below momentarily.
An OVP latch application example is shown in figure 15.
This circuit protects the system by causing latch operation in the event of an overload or load short. In
the steady state, the error amp input/output pins operate at 2.5 V typ., but if the load becomes heavy the
FB pin level drops and the COMP pin level rises. As shown in the figure, this is detected by the
HA17431 shunt regulator, and the FB pin level is pulled up, operating the OVP latch.
The operation parameters are as follows:
COMP pin voltage detection level: Vth = (R
FB
HA17384SPS/SRP, HA17384HPS/HRP, HA17385HPS/HRP
2
Figure 15 Example of OVP Latch Application Circuit
2.5V
7.0V
+
+
OVP
EA
Error amplifier
OVP comparator
Inside IC
1
+ R
1
COMP
2SA1029
2
) / R
R
R
V
1
2
IN
2
10k
47k
2.5 V
R
10k
1k
HA17431
(Vref
External circuit
(only partially shown)
3
2.5V)
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