ST72141K2 datasheet(61/132 Pages) STMICROELECTRONICS

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ST72141K

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MOTOR CONTROLLER (Cont’d)

The measurement window frequency can be pro-

grammed between 195Hz and 25KHz by the

means of the SA[3:0] bits in the MPRSR register.

In sensorless mode this measurement window can

be used to detect either End of Demagnetization

or BEMF zero crossing events. Its width can be

defined between 5

µs and 30µs in sensorless

mode by the OT[1:0] bits in the MPOL register. In

sensor mode (SR=1) this off time is fixed at

1.25

µs.

Table 22. Off-Time Table

Table 23. Sampling Frequency Selection

Figure 38. Sampling clock generation block

OT1

bit

OT0

bit

Off-Time

Sensorless Mode

(SR bit=0)

Off-Time

Sensor Mode

(SR bit =1)

µs

1.25

µs

SA3

SA2

SA1

SA0

Sampling Frequency

0000

25.0 KHz

0001

20.0 KHz

0010

18.1 KHz

0011

15.4 KHz

0100

12.5 KHz

0101

10.0 KHz

0110

6.25 KHz

0111

3.13 KHz

1000

1.56 KHz

1001

1.25 KHz

1010

1.14 KHz

1011

961 Hz

1100

781 Hz

1101

625 Hz

1110

390 Hz

1111

195 Hz

Frequency logic

4 MHz1

Off-Time logic

SA[3:0] bits

OT[1:0] bits

Toff

Tsampling

(1) The MTC controller input frequency must always be 4 MHz,

whatever the crystal frequency is. The appropriate internal

frequency can be selected in the Miscellaneous register.

MPRSR Register

MPOL Register

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