603
Motor driver ICs
3-phase motor driver
BA6458FP-Y
The BA6458FP-Y is an one-chip IC designed for driving video cassette recorder cylinder motors. It is a high-performance
IC with a 3-phase, full-wave, pseudo-linear drive system. The IC is compactly packaged.
F
Applications
Video cassette recorder cylinder motors
F
Features
1) 3-phase, full-wave, pseudo-linear drive system.
2) Output saturation voltage is low with low variation.
3) Built-in torque limit pin.
4) Contains two amplifiers and two hysteresis amplifi-
ers to amplify FG and PG signals.
5) Built-in thermal shutdown circuit.
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Block diagram
606
Motor driver ICs
BA6458FP-Y
F
Circuit operation
(1)
The 3-phase Hall signal is amplified in the hall am-
plifiers and sent to the matrix section, where the signal is
further amplified and combined. After the signal is con-
verted to a current in the amplitude control circuit, the cur-
rent is supplied to the output driver, which then provides
a motor drive current. The phases of the Hall input signal,
output voltage, and output current are shown in Fig. 1.
(2)
Torque control pin
The output current can be controlled by adjusting the
voltage applied to the torque control pin (pin 9).
(3)
Start / stop pin
The motor is in the run mode when the pin input voltage
is 3.5V or more and in the idle mode (all output transistors
are off) when the voltage is 1.2V or less.
(4)
Power ground pin (R
NF
pin)
The R
NF
pin is the output stage ground pin. Connect a re-
sistor (0.5
recommended) between this pin and the
ground to monitor the output current.
(5)
Torque limit pin (TL pin)
The output current can be limited by applying a voltage
to the torque limit pin. Control is provided so that this pin
will have the same potential as the R
NF
pin. Note that
there is an offset in the TL-pin voltage.
(6)
Phase compensation pin (C
NF
pin)
Connect a capacitor between this pin and V
CC
if the out-
put tends to oscillate.
(7)
Amplifiers 1 and 2
Amplifiers 1 and 2 have an open loop gain of about 70dB
(typical). The input terminals are biased internally to
2.45V (typical).
(8)
Hysteresis amplifiers
The hysteresis amplifiers have a hysteresis width of
120mV (typical). The input terminals are biased inter-
nally.
607
Motor driver ICs
BA6458FP-Y
F
Operation notes
(1)
Input / output circuit
(
1) Start / stop switching pin (25 pin)
(
2) Torque limit pin (18 pin)
(
3) Torque control input (9 pin)
(
4) Driver output (A1: 24 pin, A2: 22 pin, A3: 21 pin)
(
5) Hall input
(H1
+
: 1 pin, H1
*
: 2 pin, H2
+
: 3 pin, H2: 4 pin,
H3
+
: 5 pin, H3
*
: 6 pin)
(
6) I / O of amplifiers 1 and 2
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