Datasheet BA6832FS Datasheet (ROHM)

Motor driver ICs

Voice coil motor driver

BA6832FS

The BA6832FS is a voice coil motor driver used for moving the heads of hard disc and mass-storage floppy disc drives.
Applications

HDD disc and mass-storage FDD
Features

1) Output current is controlled by the Vctl-Vref voltage.

2) Retraction control pin.

Absolute maximum ratings (Ta = 25C)

3) Chip enabling pin.

4) Internal thermal shutdown circuit.

Recommended operating conditions

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Motor driver ICs BA6832FS

Block diagram

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Motor driver ICs BA6832FS

Pin descriptions

Input / output circuits

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Motor driver ICs BA6832FS

Electrical characteristics (unless otherwise noted, Ta = 25C and VCC = 12V)

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Motor driver ICs BA6832FS

Circuit operation
(1) Output current control
The method of output current control depends on wheth­er the RTL pin is HIGH or LOW.

(1) When the RTL pin is LOW

The voltage V
tween pins 10 and 11 (with reference to pin 10) is con­trolled by the voltage between Vctl (pin 18) and Vref (pin

19) :
V

RS=(VctlVref)1 (Typ.)

The output current I

O=(VctlVref) / Rs (Typ.)

I

where the positive direction is from pin 13 to pin 10.
Therefore, the voltage-current conversion gain for the
control input is determined by the R
band width in this case is 80kHz (typical).

(2) When the RTL pin is HIGH

The V
the Vrtr (pin 17) voltage (with reference to the ground) :

RS=0.1Vrtr / Rs

V

(3) RTR threshold

The RTR pin threshold voltage is 1.21.3V . The pin has
a hysteresis width of about 40mV.
(2) Standby mode
The standby mode is activated when the CE pin is LOW;
the circuit current is reduced to 0.15mA (typical), and the
output pins are put to the high impedance state. The op­eration mode is activated when the CE pin is HIGH, and
the output current becomes controllable. The pin’s
threshold voltage is 1.21.3V.
(3) Internal reference voltage
The internal reference voltage V

reg=(VCCVF)/2

V

where V
and 13) operate with reference to V

RS that develops across the resistor RS be-

O is given by :

S value. The gain

RS voltage (with reference to pin 10) is controlled by

reg is given by :

reg=5.65 when VCC=12V . The output pins (pins 10

reg.

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Motor driver ICs BA6832FS

Application example

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Motor driver ICs BA6832FS

Operation notes
(1) Thermal shutdown circuit
The IC has a built-in thermal shutdown circuit. The circuit
turns off all the driver outputs when the chip junction tem­perature rises to about 175C (typical). There is a tem­perature difference of 20C (typical) between the tem­peratures at which the circuit is activated and
deactivated.
(2) Vctl, Vref, and input pins
If voltage is applied to Vctl (pin 18) and V

CC voltage is outside the operating voltage, the driv-

the V

ref (pin 19) when

er outputs are turned on and a current may flow through
the connected motor. The voltage of each input pin
should be less than V

CC and more than the ground volt-

age.

Electrical characteristic curves

(3) Temperature dependence of quiescent circuit cur­rent (I

CC)

When the IC temperature rises with Vctl=V
CE=LOW in the quiescent mode, I

CC may increase due

ref and

to the temperature dependence of the standby current
that flows through the high- and low-side transistors.
(4) Package power dissipation
The IC power dissipation changes greatly with the supply
voltage and the output current. Give full consideration to
the power dissipation rating when setting the supply volt­age and the output current.

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Motor driver ICs BA6832FS

External dimensions (Units: mm)

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