Rainbow-electronics BA6950FS Manual de usuario descargar pdf (Pagina 4)

487

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 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

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

RT1) = V2 pin/R1 S S S

S I15 pin (IRT2)

I15 pin (I

RT2) = I8 pinR5/R4 S S S

S V16 pin (VRT1)

V16 pin = R3  (I16 pinI15 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-

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.

1 2 3 4 5 6

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