484

Motor driver ICs

Reversible motor driver

BA6950FS

The BA6950FS is a reversible-motor driver suited for brush motors. Two logic inputs allow four output modes: forward,
reverse, stop (standby), and brake. The rotational speed of motor can be set arbitrarily by changing the voltage applied
to the motor with control pins. The IC can also drive a motor at a constant speed by using a built-in current feedback
amplifier.

Applications

VCRs, audio equipment

Features

1) Two logic inputs allow four output modes: forward, re-

verse, stop (standby), and brake.

2) Motor speed variable with voltage control signals.

3) Built-in current feedback amplifier allows constant

motor speed.

4) Control gain can be set arbitrarily by using external

resistors.

5) Built-in thermal shutdown circuit.

Absolute maximum ratings (Ta = 25

Recommended operating conditions (Ta = 25

487

Motor driver ICs

BA6950FS

Electrical characteristics (unless otherwise noted, Ta = 25

C, V

= 4.8V, VB = 4.8V)

Circuit operation

(1)

Input section (F

, R

)

Control signals are input from these pins. Current flows
from M2 to M1 (forward mode) when F

is HIGH and R

is LOW, and from M1 to M2 (reverse mode) when R

HIGH and F

is LOW. Putting F

and R

both HIGH re-

sults in the brake mode in which the high-side output
transistor is turned off to shut down the motor driving cur-
rent and the low-side output transistor is turned ON to ab-
sorb the counter-electromotive force of the motor, so that
a brake is put on the motor. When F

and R

are both

LOW, both M1 and M2 are left open and the motor stops.
Input / output truth table

(2)

Output section (M1, M2)

Two logic inputs control the motor by changing the status
of bridge-configured transistors.

(3)

Output high level voltage

Values of current, voltage, and HIGH level output voltage
can be set as follows by using external resistors (refer to
the application circuit of Fig. 4).

I16 pin (I

RT1

)

I16 pin (I

RT1

) = V2 pin/R1

I15 pin (I

RT2

)

I15 pin (I

RT2

) = I8 pin

R5/R4

V16 pin (V

RT1

)

V16 pin = R3

(I16 pin

)

I15 pin)

)

I16 pin

V7, 9 pin (M1, M2 voltage; high-side voltage)

V7, 9 pin = 4

V16 pin (Typ.)

(4)

Current feedback amplifier

The pin-8 current is increased when the motor rotational
speed is reduced by loading, and the current feedback
amplifier increases the pin-15 current according to equa-
tion

. Because the pin-16 voltage then increases ac-

cording to equation

, the HIGH level output voltage

also increases according to equation

. In this way, the

rotational speed is kept constant by increasing the volt-
age applied to the motor.

488

Motor driver ICs

BA6950FS

Application example

Operation notes

(1)

Thermal shutdown circuit

The thermal shutdown (TSD) circuit turns off all driver
outputs when the IC junction temperature rises above
175

C (Typ.). The temperature difference between the

activation and deactivation settings is about 20

Temperature setting of TSD

(2)

Control logic and control signal input pins

Voltage should never be applied to the control logic input
pins (pins 5 and 10) or the control signal input pin (pin 2)
when the V

voltage is not applied to the IC. Similarly,

the voltage on each input pin should not exceed any ap-
plied V

voltage.

(3)

PCB arrangement

When changing the rotational direction of a motor, a large

current of up to a few hundred milliamperes can flow be-
tween the motor power supply (pin 6) and RNF (pin 8).
Depending on the application, this large output current
may flow back to input pins, resulting in output oscillation
or other malfunctions. Make sure that your design does
not allow a common impedance between the large cur-
rent output lines and the input section. Suppress the
power supply impedance to low levels, otherwise output
oscillation may occur.
(4)

Package power

The power dissipated by the IC varies widely with the
supply voltage and the output current. Give full consider-
ation to the package power dissipation rating when set-
ting the supply voltage and the output current.
(5)

The input pins (pins 5 and 10) have temperature-

dependent characteristics. Take the temperature effect
into consideration when using the IC.
(6)

To eliminate motor noise, connect a capacitor be-

tween M1 (pin 7) and GND and between M2 (pin 9) and
GND.

Fig.4

Электронный компонент: BA6950FS