m51996ap Renesas Electronics Corporation., m51996ap Datasheet - Page 33

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

M51996AP/AFP
At the start of the operation, there happen to be no output pulse due to F/B terminal current through C1 and C2, as the
potential of F/B terminal rises sharply just after the start of the operation.
Not to lack the output pulse, is recommended to connect the capacitor C4 as shown by broken line.
Please take notice that the current flows through the R1 and R2 are superposed to I
connected to C
How to Get The Narrow Pulse Width During The Start of Operation
Figure 37 shows how to get the narrow pulse width during the start of the operation. If the pulse train of forcedly
narrowed pulse-width continues too long, the misstart of operation may happen, so it is recommended to make the
output pulse width narrow only for a few pulse at the start of operation. 0.1 F is recommended for the C.
How to Synchronize with External Circuit
Type M51996A has no function to synchronize with external circuit, however, there is some application circuit for
synchronization as shown in figure 38.
REJ03D0836-0201 Rev.2.01 Nov 14, 2007
Page 33 of 35
Figure 37 How to Get The Narrow Pulse Width During The Start of Operation
VCC2
as shown in figure 18.
Oscillating
waveform
Synchronize
waveform
Figure 38 How to Synchronize With External Circuit
R
Minimum pulse width of
synchronous pulse
ON
T-ON
M51996A
C
F
CF
R
OFF
T-OFF
M51996A
F/B
Q1
Maximum pulse width of
synchronous pulse
To photo
coupler
Synchronous
pulse
100 Ω
C
CC(START)
0 V
0 V
. Not to superpose, R1 is