m51971 Mitsumi Electronics, Corp., m51971 Datasheet - Page 7

• Manufacturer Part Number: m51971
• Description: Motor Speed Control
• Manufacturer: Mitsumi Electronics, Corp.

Non-inverted input
power supply turned ON.
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
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
1
is characteristic to the IC. The frequency of the
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