LM621 National Semiconductor, LM621 Datasheet - Page 6

• Manufacturer Part Number: LM621
• Description: LM621 Brushless Motor Commutator
• Manufacturer: National Semiconductor

Three-Phase Motor Commutation
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
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-
Phasing
Pin Numbers
Sensor
‘‘120 deg’’
‘‘240 deg’’
‘‘300 deg’’
30 deg
60 deg
90 deg
Alternate
‘‘60 deg’’
Phasing
120–180
180–240
240–300
300–360
120–180
180–240
240–300
300–360
180–270
270–360
Position
60–120
60–120
90–180
Range
0–60
0–60
0–90
120–180
180–240
240–300
300–360
120–180
180–240
240–300
300–360
120–180
180–240
240–300
300–360
120–180
180–240
240–300
300–360
Position
60–120
60–120
60–120
60–120
Range
0–60
0–60
0–60
0–60
HS1
0
0
0
1
1
1
1
1
1
0
0
0
0
0
1
1
5
TABLE I LM621 Commutation Decoder Truth Table
HS1
TABLE II Alternative Sensor-Phasing Names
Sensor Inputs
0
1
1
1
0
0
0
1
1
1
0
0
0
1
1
1
0
0
0
1
1
1
0
0
HS2
Sensor Inputs
0
0
1
1
1
0
0
0
1
1
1
0
1
0
0
1
6
HS2
0
0
1
1
1
0
0
0
0
1
1
1
1
1
0
0
0
1
1
1
1
0
0
0
(Continued)
HS3
HS2
HS2
HS2
HS2
0
1
1
1
0
0
1
0
0
0
1
1
7
6
HS3
0
0
0
1
1
1
1
1
0
0
0
1
0
0
0
1
1
1
1
1
0
0
0
1
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
ON
ON
ON
ON
ON
off
off
off
off
off
off
off
off
off
off
off
16
1
Sink Outputs
Same as 30-degree phasing but in reverse
order i e only change is relative direction
Same as 60-degree phasing but with shifted
order of position ranges i e only change is
relative phasing of sensor signals
Same comment as above for ‘‘120 deg’’
phasing
Same as 30-degree phasing but with shifted
order of position ranges i e only change is
relative phasing of sensor signals
ON
ON
ON
ON
off
off
off
off
off
off
off
off
na
na
na
na
15
2
Corresponding LM621 Position
Range and or Comments
ON
ON
ON
ON
ON
off
off
off
off
off
off
off
off
off
off
off
14
3
ON
ON
ON
ON
ON
off
off
off
off
off
off
off
off
off
off
off
13
1
Source Outputs
ON
ON
ON
ON
off
off
off
off
off
off
off
off
na
na
na
na
12
2
ON
ON
ON
ON
ON
off
off
off
off
off
off
off
off
off
off
off
11
3