M51995AP

Manufacturer Part NumberM51995AP
DescriptionSwitching regulator control
ManufacturerMITSUBISHI
M51995AP datasheet
 


1
2
3
4
5
6
7
8
9
10
11
Page 11
12
Page 12
13
Page 13
14
Page 14
15
Page 15
16
Page 16
17
Page 17
18
Page 18
19
Page 19
20
Page 20
21
22
23
24
25
26
27
Page 19/27:

Output section

Download datasheet (462Kb)Embed
PrevNext
Vcc
7.8V
8k
12k
Q1
Q2
400
OVP
2.5k
I
2
GND
I1=0 when OVP operates
Fig.22 Detail diagram of OVP circuit
8
OVP RESET POINT
8.82V(-30°C)
7
8.97V(25°C)
9.07V(85°C)
6
5
Ta=-30°C
Ta=25°C
4
Ta=85°C
3
2
1
0
10
15
25
30
5
20
0
SUPPLY VOLTAGE Vcc(V)
Fig.23 CIRCUIT CURRENT VS. SUPPLY VOLTAGE
(OVP OPERATION)

Output section

It is required that the output circuit have the high sink and
source abilities for MOS-FET drive.It is well known that the
100µA
"totempole circuit has high sink and source ability.However,it
has the demerit of high through current.
I
1
For example,the through current may reach such the high
current level of 1A,if type M51995A has the "conventional"
totempole circuit.For the high frequency application such as
higher than 100kHz,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 100mA.
Q3
APPLICATION NOTE OF TYPE M51995AP/FP
Design of start-up circuit and the power supply
of IC
(1)The start-up circuit when it is not necessary to set the
start and stop input voltage
Fig.24 shows one of the example circuit diagram of the start-up
circuit which is used when it is not necessary to set the start
and stop voltage.
It is recommended that the current more than 300µA flows
through R1 in order to overcome the operation start-up current
Icc
and Cvcc is in the range of 10 to 47µF.The product of
(START)
R1 by Cvcc causes the time delay of operation,so the response
time will be long if the product is too much large.
RECTIFIED DC
VOLTAGE FROM
SMOOTHING CAPACITOR
M51995A
35
40
Fig.24 Start-up circuit diagram when it is not
necessary to set the start and stop input voltage
Just after the start-up,the Icc current is supplied from
Cvcc,however,under the steady state condition ,IC will be
supplied from the third winding or bias winding of
transformer,the winding ratio of the third winding must be
designed so that the induced voltage may be higher than the
operation-stop voltage Vcc
The Vcc voltage is recommended to be 12V to 17V as the
normal and optimum gate voltage is 10 to 15V and the output
voltage(V
) of type M51995AP/FP is about(Vcc-2V).
OH
(
/ 27 )
19
M51995AP/FP
SWITCHING REGULATOR CONTROL
MAIN TRANSFORMER
R1
VF
THIRD WINDING OR
Vcc
BIAS WINDING
CVcc
GND
.
(STOP)