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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, reverse, stop (standby), and brake.
2) Motor speed variable with voltage control signals.
Absolute maximum ratings (Ta = 25C)
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.
Recommended operating conditions (Ta = 25C)
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Motor driver ICs BA6950FS
Block diagram
Pin descriptions
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Motor driver ICs BA6950FS
Input/output circuit (resistances, in Ω, are typical values)
(1) R and F inputs (pins 5 and 10)
(3) Motor output (pins 6, 7, 8, and 9)
(2) CTL amplifier (pins 2 and 3)
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Motor driver ICs BA6950FS
FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 4.8V, VB = 4.8V)
FCircuit operation
(1) Input section (F
IN, RIN)
Control signals are input from these pins. Current flows
from M2 to M1 (forward mode) when F
IN is HIGH and RIN
is LOW, and from M1 to M2 (reverse mode) when RIN is
HIGH and F
IN is LOW. Putting FIN and RIN both HIGH re-
sults in the brake mode in which the high-side output
transistor is turned off to shut down the motor driving current and the low-side output transistor is turned ON to absorb the counter-electromotive force of the motor, so that
a brake is put on the motor. When F
IN and RIN 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).
S I16 pin (IRT1)
I16 pin (I
S I15 pin (IRT2)
I15 pin (I
S V16 pin (VRT1)
RT1) = V2 pin/R1 S S S
RT2) = I8 pinR5/R4 S S S
V16 pin = R3 (I16 pinI15 pin)R2 I16 pin
S S S
S V7, 9 pin (M1, M2 voltage; high-side voltage)
V7, 9 pin = 4 V16 pin (Typ.)
S S S
(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-
2
. Because the pin-16 voltage then increases ac-
tion
3
cording to equation
also increases according to equation
, the HIGH level output voltage
4
. In this way, the
rotational speed is kept constant by increasing the voltage applied to the motor.
1
2
3
4
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Motor driver ICs BA6950FS
FApplication example
FOperation 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_C.
STemperature 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
CC voltage is not applied to the IC. Similarly,
the voltage on each input pin should not exceed any applied V
CC voltage.
(3) PCB arrangement
When changing the rotational direction of a motor, a large
488
Fig.4
current of up to a few hundred milliamperes can flow between 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 current 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 consideration to the package power dissipation rating when setting the supply voltage and the output current.
(5) The input pins (pins 5 and 10) have temperaturedependent characteristics. Take the temperature effect
into consideration when using the IC.
(6) To eliminate motor noise, connect a capacitor between M1 (pin 7) and GND and between M2 (pin 9) and
GND.
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Motor driver ICs BA6950FS
Electrical characteristic curves
External dimensions (Units: mm)
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