Datasheet BA6826FS, BA6825FS Datasheet (ROHM)

Motor driver ICs

2-phase motor driver for VCR cylinder
motors

BA6825FS / BA6826FS

The BA6825FS and BA6826FS are direct-drive motor drivers suitable for 2-phase, full-wave linear motors. They consist
of a Hall amplifier control circuit and driver circuits.

Applications
VCR cylinder motors

Features

1) Linear drive system provides low switching noise.

2) Constant supply voltage pin for hall devices.

3) High ratio of output current against control current.
(4000 Typ.)

Block diagram

4) Available in compact surface-mount packages.

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Motor driver ICs BA6825FS / BA6826FS

FAbsolute maximum ratings (Ta = 25_C)

FRecommended operating conditions

FElectrical characteristics (unless otherwise noted, Ta = 25_C, V

FPin descriptions

CC = 12V)

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Motor driver ICs BA6825FS / BA6826FS

Input / output circuits
(1) Hall and ECI inputs (2) Coil output

Circuit operation
(1) The signal from the Hall device is amplified by the
Hall amplifier and then supplied to the driver circuit. The
driver gain, which is constant, is regulated by changing
the Hall amplifier gain with the input current on the output
current control pin (E

CI pin). The motor rotational speed

is sensed by the FG, and the output of which is F / I-con­verted and supplied to the E

CI pin as a feedback signal,

so that a constant rotational speed is maintained as fol­lows :

(1) The motor speed decreases.
(2) The speed control IC outputs a feedback signal to the

ECI pin.

(3) The Hall amplifier gain increases.
(4) The output current increases.
(5) The motor speed increases.

(2) When the voltage on Hall INφ
voltage on Hall INφ

1 (), an output current flows from

OUT1 () to OUT1 () according to the voltage differen­tial. When the voltage on Hall INφ
other hand, an output current flows from OUT1 () to
OUT1 ().
Similarly , when the voltage on Hall INφ
the voltage on Hall INφ

2 (), an output current flows from

OUT2 () to OUT2 () according to the voltage differen­tial. When the voltage on Hall INφ
other hand, an output current flows from OUT2 () to
OUT2 ().

1 () is higher than the

1 () is higher, on the

2 () is higher than

2 () is higher, on the

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Motor driver ICs BA6825FS / BA6826FS

(3) Output waveforms are shown in Fig. 5. Because of
the amplifier offset, the output is left OPEN when the out­put signal switches from positive to negative. The output
waveform is determined by the external circuit because
the IC impedance increases during this transition period.
Since inductive loads are usually provided, a capacitor
should be connected to suppress the backlash voltage.

FOperation notes
(1) E

CI input

The ECI input circuit has 2V

F and a 500Ω resistor con-

nected in series. Current is limited only by the 500Ω re-
sistor.
(2) Hall input
Signals of 50mV (peak to peak) or greater should be ap­plied to the Hall device input. The DC input range is be­tween 2V and (Vreg1.5V). There will be no problem if

the input is centered around Vreg / 2.
Because the Hall input impedance is 1MΩ or grater, any
type of Hall device can be connected. No current flows
when the transistor is off because the Hall input pins (
and ) are differential.
Because the ICs are linear drivers, any DC offset in the
Hall device will be amplified and appear in the output.
Use Hall devices having a minimum offset. Hall devices
can be connected in either series or parallel.

(3) Thermal shutdown circuit
The circuit puts the driver outputs (9, 11, 12, and 14 pin)
to the open state at the temperature of 175_C (typical).
There is a temperature difference of about 20_C between
the temperatures at which the circuit is activated and
deactivated.

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Motor driver ICs BA6825FS / BA6826FS

Application examples

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Motor driver ICs BA6825FS / BA6826FS

Electrical characteristic curves

External dimensions (Units: mm)

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