M51995AP

Manufacturer Part NumberM51995AP
DescriptionSwitching regulator control
ManufacturerMITSUBISHI
M51995AP datasheet
 


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CT
C
T
M51995A
OVP
Fig.39 Application circuit diagram to keep the
non-operating condition when over load
current condition will continue for specified
duration
Output circuit
(1)The output terminal characteristics at the Vcc voltage
lower than the "Operation-stop" voltage
V
OUT
M51995A
Fig.40 Circuit diagram to prevent the MOS-FIT gate
potential rising
The output terminal has the current sink ability even though the
Vcc voltage lower than the "Operation-stop" voltage or Vcc(
(It means that the terminal is "Output low state" and please refer
characteristics of output low voltage versus sink current.)
This characteristics has the merit not to damage the MOS-FIT
at the stop of operation when the Vcc voltage decreases lower
than the voltage of Vcc(
),as the gate charge of MOS-
STOP
FIT,which shows the capacitive load characteristics to the
output terminal,is drawn out rapidly.
The output terminal has the draw-out ability above the Vcc
voltage of 2V,however,lower than the 2V,it loses the ability and
the output terminal potential may rise due to the leakage
current.
In this case, it is recommended to connect the resistor of 100k
between gate and source of MOS-FIT as shown in Fig.40.
(2)MOS-FIT gate drive power dissipation
Fig.41 shows the relation between the applied gate voltage
and the stored gate charge.
In the region 1 ,the charge is mainly stored at C
depletion is spread and C
is small owing to the off-state of
GD
MOS-FIT and the high drain voltage.
In the region 2 ,the C
is multiplied by the "mirror effect" as
GD
the characteristics of MOS-FIT transfers from off-state to on-
state.
In the region 3 ,both the C
and C
GD
GS
characteristics as the MOS-FIT is on-state and the drain
voltage is low.
Vcc
20
15
10
5
1
0
0
TOTAL STORED GATE CHARGE(nC)
Fig.41 The relation between applied gate-source
TO MAIN
voltage and stored gate charge
TRANSFORMER
The charging and discharging current caused by this gate
charge makes the gate power dissipation.The relation between
gate drive current I
R
100k
CLM
following equation;
I
=Q
D
Where
f
OSC
As the gate drive current may reach up to several tenths
milliamperes at 500kHz operation,depending on the size of
)
MOS-FIT,the power dissipation caused by the gate current can
STOP
not be neglected.
In this case,following action will be considered to avoid heat
up of type M51995A.
(1) To attach the heat sink to type M51995A
(2) To use the printed circuit board with the good thermal
conductivity
(3) To use the buffer circuit shown next section
(3)Output buffer circuit
It is recommended to use the output buffer circuit as shown in
Fig.42,when type M51995A drives the large capacitive load or
bipolar transistor.
as the
GS
affect to the
(
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24
MITSUBISHI (Dig./Ana. INTERFACE)
M51995AP/FP
SWITCHING REGULATOR CONTROL
V
=80V
DS
V
=200V
DS
V
=320V
DS
3
GATE
2
I
=4A
D
20
8
12
16
4
and total gate charge Q
D
GSH
.....................................(11)
• f
GSH
OSC
is switching frequency
DRAIN
I
D
C
GD
C
DS
V
D
C
GS
V
GS
SOURCE
is shown by