Technical Note

6/10

BA6950FS, BA6951FS

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2011.05 - Rev.C

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External application components

1) Resistor for the current sensing, R5

This is a current sensing resistor, care must be taken to avoid changes in the ground wire pattern in any external

connected component.

2) Control amplifier gain setting resistor, R1

decided here is output to RT1 pin.

3) Control amplifier phase compensation capacitor, C1

This phase compensation capacitor for the control amplifier. Please monitor the RT1 pin voltage and confirm no

oscillation. About 33pF is recommended.

4) Current feedback amplifier gain setting resistor, R4

CS1 pin voltage (the motor current detection) is buffered to CS2 pin - BA6950FS.

ATC pin voltage (the motor current detection) is buffered to CS pin - BA6951FS.

The current feedback gain can be set by R4 connecting to CS2 or CS pin. The current decided here is output to RT2

pin.

5) Pre-amplifier gain setting resistor, R2, R3

These resistors are to add the control amplifier output and the current feedback amplifier output. This amplifier has

about fourfold gain.

6) Pre-amplifier phase compensation capacitor, C2

Please connect the capacitor about 0.1µF as the phase compensation of the pre-amplifier, and monitor the driver

output no oscillation.

7) Stabilization capacitor for the power supply line, C5, C6

Please connect the capacitor of 1μF to 100μF for the stabilization of the power supply line, and confirm the motor

operation.

8) Phase compensating capacitor, C3, C4

Noise is generated in output pins or oscillation results in accord with the set mounting state such as power supply

circuit, motor characteristics, PCB pattern artwork, etc. As noise oscillation measures, connect 0.01μF to 0.1μF

capacitors.

9) Torque limiter setting, TL pin, BA6951FS only

The motor current is limited so that ATC pin voltage should not exceed TL pin voltage.

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Functional descriptions

Table 3 Logic table

FIN

RIN

M1

M2

Operation

L

L

OPEN*

OPEN*

Stop (idling)

H

L

L

H

Forward (M2 > M1)

L

H

H

L

Reverse (M1 > M2)

H

H

L

L

Brake (stop)

* OPEN is the off state of all output transistors. Please note that this is the state of the connected diodes, which differs from that of the mechanical relay.