M51995AP/AFP
As the OVP reset voltage is settled on the rather high voltage of 9.0 V, SMPS can be reset in rather short time from the
switch-off of the AC power source if the smoothing capacitor is not so large value.
VCC
7.8 V
100 µA
8 k
I1
12 k
Q1
Q2
400
OVP
GND
Q3
2.5 k
I2
Note: I1 = 0 when OVP operates
Figure 20 Detail Diagram of OVP Circuit
8
Ta = 25 °C
Ta = 85 °C
Ta = −30 °C
7
6
5
4
3
2
1
0
OVP reset point
8.82 V (−30 °C)
8.97 V (25 °C)
9.07 V (85 °C)
0
5
10 15 20 25 30 35 40
Supply Voltage VCC (V)
Figure 21 Circuit Current vs. Supply Voltage (OVP Operation)
Output Section
It is required that the output circuit has the high sink and source abilities for MOS FET drive. It is well known that the
totempole circuit has high sink and source ability. However, it has the demerit of high through current.
For example, the through current may reach such the high current level of 1 A, if type M51995A has the “conventional”
totempole circuit. For the high frequency application such as higher than 100 kHz, this through current is very
important factor and will cause not only the large ICC current and the inevitable heat-up of IC but also the noise voltage.
This IC uses the improved totempole circuit, so without deteriorating the characteristic of operating speed, its through
current is approximately 100 mA.
REJ03D0835-0300 Rev.3.00 Jun 06, 2008
Page 27 of 40
RENESAS [ RENESAS TECHNOLOGY CORP ]
