m51996ap Renesas Electronics Corporation., m51996ap Datasheet - Page 25

• Manufacturer Part Number: m51996ap
• Description: Switching Regulator Control
• Manufacturer: Renesas Electronics Corporation.

M51996AP/AFP
OVP Circuit
1. To avoid the miss operation of OVP
2. Application circuit to make the OVP-reset time fast
REJ03D0836-0201 Rev.2.01 Nov 14, 2007
Page 25 of 35
It is recommended to connect the capacitor between OVP terminal and GND for avoiding the miss operation by the
spike noise.
The OVP terminal is connected with the sink current source ( 150 A) in IC when OVP does not operate, for
absorbing the leak current of the photo coupler in the application.
So the resistance between the OVP terminal and GND for leak-cut is not necessary.
If the resistance is connected, the supply current at the OVP reset supply voltage becomes large.
As the result, the OVP reset supply voltage may become higher than the operation stop voltage.
In that case, the OVP action is reset when the OVP is triggered at the supply voltage a little high than the operation
stop voltage.
So it should be avoided absolutely to connect the resistance between the OVP terminal and GND.
The reset time may becomes problem when the discharge time constant of C
circuit condition, it is recommend to discharge the C
OVP-reset time fast.
Figure 20 Example Circuit Diagram to Make The OVP-reset-time Fast
Figure 19 Peripheral Circuit of OVP Terminal
M51996A
The time constant of
this part should be short
V
GND
CC
VCC
OVP
forcedly and to make the V
To REG or V
C
+
FIN
+
5.6 k
R2
R1
Photo coupler
CC
C
+
VCC
FIN
To main
transformer
M51996A
(R1
CC
V
GND
low value; This makes the
CC
R2) is long. Under such the