m51996ap Renesas Electronics Corporation., m51996ap Datasheet - Page 32

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

M51996AP/AFP
3. Output buffer circuit
DET Circuit
Figure 35 shows how to use the DET circuit for the voltage detector and error amplifier.
For the phase shift compensation, it is recommended to connected the CR network between DET terminal and F/B
terminal.
Figure 36 shows the gain-frequency characteristics between point B and point C shown in figure 35.
The G1, 1 and 2 are given by following equations;
REJ03D0836-0201 Rev.2.01 Nov 14, 2007
Page 32 of 35
As the gate drive current may reach up to several tenths milliamperes at 500 kHz operation, depending on the size of
MOS FET, the power dissipation caused by the gate current can not be neglected.
In this case, following action will be considered to avoid heat up of type M51996A.
(1) To attach the heat sink to type M51996A
(2) To use the printed circuit board with the good thermal conductivity
(3) To use the buffer circuit shown next section
It is recommended to use the output buffer circuit as shown in figure 34, when type M51996A drives the large
capacitive load or bipolar transistor.
G1 =
ω
ω
Figure 36 Gain-frequency Characteristics Between Point B and C Shown in Figure 35
1
2
=
=
C2 • R3
C1 • C2 • R3
R1 / R2
C1 + C2
1
R3
Figure 35 How to Use The DET Circuit for The Voltage Detector
………………………… (11)
……………………… (10)
………………… (12)
M51996A
Figure 34 Output Buffer Circuit Diagram
G1
M51996A
Log ω
DET
F/B
C
G
(DC voltage gain)
ω
C4
1
C2
AVDET
V
OUT
C1
R3
ω
2
R1
R2
A
B
Detecting
voltage