M51996AP Datasheet, PDF (23/36 Pages) Mitsubishi Electric Semiconductor – SWITCHING REGULATOR CONTROL

M51996AP/AFP
When the third winding is the “fly back winding” or “reverse polarity”, the V_IN(START) can be fixed, however,
V_IN(STOP) can not be settled by this system, so the auxiliary circuit is required.
Rectified DC
voltage from
smoothing capacitor ^VIN
N_P
Primary winding
of transformer
R1
V_CC
M51996A
GND
V_F Third winding of
N_B ^transformer
+
R2
C_VCC
Figure 16 Start-up Circuit Diagram When It is Not Necessary to Set The Start and Stop Input Voltage
3. Notice to the V_CC, V_CC line and GND line
Collector
V_CC
Output
M51996A
R_CLM
Emitter
GND
+
C_VCC
Main
transformer
third winding
Figure 17 How to Design The Conductor-pattern of Type M51996A on PC Board
(schematic example)
To avoid the abnormal IC operation, it is recommended to design the V_CC is not vary abruptly and has few spike
voltage, which is induced from the stray capacity between the winding of main transformer.
To reduce the spike voltage, the C_VCC, which is connected between V_CC and ground, must have the good high
frequency characteristics.
To design the conductor-pattern on PC board, following cautions must be considered as shown in figure 17.
(1) To separate the emitter line of type M51996A from the GND line of the IC
(2) The locate the C_VCC as near as possible to type M51996A and connect directly
(3) To separate the collector line of type M51996A from the V_CC line of the IC
(4) To connect the ground terminals of peripheral parts of ICs to GND of type M51996A as short as possible
REJ03D0836-0201 Rev.2.01 Nov 14, 2007
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