M51995AFP#CF0J Renesas Electronics America, M51995AFP#CF0J Datasheet - Page 32

• Manufacturer Part Number: M51995AFP#CF0J
• Description: IC SWIT PWM SMPS OVP UVLO 20SOIC
• Manufacturer: Renesas Electronics America

Specifications of M51995AFP#CF0J

• Output Isolation: Isolated
• Frequency Range: 170 ~ 207kHz
• Voltage - Input: 9.9 ~ 36 V
• Power (watts): 1.5W
• Operating Temperature: -30°C ~ 85°C
• Package / Case: 20-SOIC (0.200", 5.30mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

M51995AP/AFP
4. Power supply circuit for easy start-up
OVP Circuit
(1) To avoid the miss operation of OVP
REJ03D0835-0300 Rev.3.00 Jun 06, 2008
Page 30 of 40
When IC starts to operate, the voltage of the C
third winding of main-transformer as the I
“unstable start-up” or “fall to start-up” may happen, as the charging interval of C
the charging does occur only the duration while the induced winding voltage is higher than the C
induced winding voltage is nearly equal to the “operation-stop voltage” of type M51995.
It is recommended to use the 10 to 47 µF for C
25.
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 µA) 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.
Figure 25 DC Source Circuit for Stable Start-up
Figure 26 Peripheral Circuit of OVP Terminal
M51995A
M51995A
V
GND
CC
CC
V
GND
of the IC increases abruptly. In case shown in figure 22 and 23, some
CC
VCC
VCC1,
begins to decrease till the C
C
and about 5 times capacity bigger than C
VCC1
OVP
+
R1
+
C
VCC2
+
10 k
Photo coupler
Main
transformer
third winding
VCC
VCC
becomes to be charged from the
is very short duration; that is
VCC1
VCC
for C
voltage, if the
VCC2
in figure