M51971FP Mitsubishi, M51971FP Datasheet - Page 7

• Manufacturer Part Number: M51971FP
• Description: MOTOR SPEED CONTROL
• Manufacturer: Mitsubishi

Non-inverted input
Brief Description on M51971 Operation
Block Description
FG amplifier
The FG amplifier consists of an operational amplifier, revel shift
circuit and diode for waveform clip.
When a DC block capacitor is connected to pin
voltage at pin
( 1.9V 3V
AC signals centering around the GND can be therefore amplified
easily. The clipper diode limits the output signal amplitude to
power supply turned ON.
Schmitt circuit
The Schmitt circuit is a comparator with histeresis, and has ON
level of V
Timer
The timer generates basic time necessary for controlling the
speed.
This timer is a one-shot circuit triggered with input signals and
generates pulse of 1.1 C R in pulse width.
Constant current control circuit
The constant current control circuit is controlled with output of timer
circuit. The circuit generates, at pin , source current of I
0.7V (V
Inverted input
LS
BE
BE
) max. and rapidly charges DC block capacitor with
+ 20mV and OFF level of V
M
).
3
becomes higher than DC voltage at pin
1
2
9
FG amplifier
V
LS
I
100
Buffer
1.9V
Operational
amplifier
D
D
OP
1
2
8
Amplifier
output
LS
- 20mV.
3
Over-shoot prevention circuit
Q
Schmitt
input
A
3
4
H
2
V
, output DC
G
LS
Over-shoot
prevention signal
Schmitt
circuit
C
1
F1
1.9V
Logic for over-shoot
prevention
by V
1
A’
– I
LS
2
Timer
8
R
Logic for timer
C
F
F2
( 190 A) for the period without one-shot pulse and generates sink
current of I
The ratio of I
tacho-generator to be set is determined by the one-short pulse
width and this current ratio (I
Where:
Over-shoot prevention circuit
The over-shoot prevention circuit operates when over-shoot is
large in particular, e.g. the motor is suddenly released from lock
status.
Q
the signal period of the tacho-generator in a motor is shorter than
the one-shot pulse. Generally, electric charge of C
for this period due to R
Buffer amplifier
The buffer circuit is a voltage follower circuit using an operational
amplifier. The input current is very small (10nA max.) and the
circuit can drive the output current of 20mA.
3
is set to ON for the period of one-short pulse width (T ) when
T
T : One-short pulse width
G
T
: Tacho-generator signal frequency (set value)
G
E
Timer output
= T x
2
( 16 A) for the period with one-shot pulse.
MITSUBISHI <CONTROL / DRIVER IC>
1
Constant current
control
to I
B
Q
I
2
1
2
I
–I
is characteristic to the IC. The frequency of the
1
2
F
Q
• C
C
1
To pin
1.09 x T
I
I
F2
MOTOR SPEED CONTROL
1
2
206 A
16 A
1
5
/ I
>>T .
R
C
6
2
D
12.6).
M51971L/FP
7.5k
comparator
15k
Stabilized voltage
Stabilized
power
supply
6
F1
is discharged
10
7
Power
supply
GND