TABLE I LM621 Commutation Decoder Truth Table

Sensor

Position

Sensor Inputs

Sink Outputs

Source Outputs

Phasing

Range

HS1

HS2

HS3

123123

0 – 60

0

0

0

ON

off

off

off

ON

off

60 – 120

0

0

1

ON

off

off

off

off

ON

30 deg

120 – 180

0

1

1

off

ON

off

off

off

ON

180 – 240

1

1

1

off

ON

off

ON

off

off

240 – 300

1

1

0

off

off

ON

ON

off

off

300 – 360

1

0

0

off

off

ON

off

ON

off

0 – 60

1

0

1

ON

off

off

off

ON

off

60 – 120

1

0

0

ON

off

off

off

off

ON

60 deg

120 – 180

1

1

0

off

ON

off

off

off

ON

180 – 240

0

1

0

off

ON

off

ON

off

off

240 – 300

0

1

1

off

off

ON

ON

off

off

300 – 360

0

0

1

off

off

ON

off

ON

off

0 – 90

0

1

HS2

off

na

off

off

na

ON

90 deg

90 – 180

0

0

HS2

ON

na

off

off

na

off

180 – 270

1

0

HS2

off

na

ON

off

na

off

270 – 360

1

1

HS2

off

na

off

ON

na

off

Pin Numbers

5

6

7

16

15

14

13

12

11

Note 1

The above outputs are generated when the Direction input pin 2 is logic high For reverse rotation (pin 2 logic low) the above sink and source output

states become exchanged

Note 2

For four-phase motors sink and source outputs number two (pins 15 and 12) are not used hense the ‘‘na’’ (not applicable) in the appropriate columns

above

Figure 6 shows how the required sink and source outputs for four-phase motors are derived

TABLE II Alternative Sensor-Phasing Names

Alternate

Position

Sensor Inputs

Corresponding LM621 Position

Phasing

Range

HS1

HS2

HS3

Range andor Comments

0 – 60

0

0

0

Same as 30-degree phasing but in reverse

60 – 120

1

0

0

order ie only change is relative direction

‘‘60 deg’’

120 – 180

1

1

0

180 – 240

1

1

1

240 – 300

0

1

1

300 – 360

0

0

1

0 – 60

0

0

1

Same as 60-degree phasing but with shifted

60 – 120

1

0

1

order of position ranges ie only change is

‘‘120 deg’’

120 – 180

1

0

0

relative phasing of sensor signals

180 – 240

1

1

0

240 – 300

0

1

0

300 – 360

0

1

1

0 – 60

0

1

0

Same comment as above for ‘‘120 deg’’

60 – 120

1

1

0

phasing

‘‘240 deg’’

120 – 180

1

0

0

180 – 240

1

0

1

240 – 300

0

0

1

300 – 360

0

1

1

0 – 60

0

1

1

Same as 30-degree phasing but with shifted

60 – 120

1

1

1

order of position ranges ie only change is

‘‘300 deg’’

120 – 180

1

1

0

relative phasing of sensor signals

180 – 240

1

0

0

240 – 300

0

0

0

300 – 360

0

0

1

Four-Phase Motor Commutation

Four-phase motors use a 90-degree (quadrature) rotor-posi-

tion sensor phasing This phasing scheme is also shown in

Table I LM621 Commutation Decoder Truth Table As

shown in Table I the 90-degree phasing has only two rotor-

position-sensor signals HS1 and HS2 When using the

LM621 to run a four-phase motor the HS2 signal is connect-

ed to both the HS2 and HS3 chip inputs

6