ST7MC1 datasheet(188/308 Pages) STMICROELECTRONICS

188 / 308 page

ST7MC1/ST7MC2

188/308

MOTOR CONTROLLER (Cont’d)

This sets the minimum off time of the PWM signal

generated by this internal clock. This off time can

vary depending on the output of the current feed-

back comparator. In sensor mode (SR=1) and

when the sampling for the Z event is done during

the PWM ON time in sensorless mode (SPLG bit is

set in MCRC register and /or DS[3:0] bits with a

value other than 000 in MCONF register), there is

no minimum OFF time required anymore, the min-

imum off time is set automatically to 0µs and the

OFF time of the PWM signal is controlled only by

the current regulation loop.

Table 47. Sampling Frequency Selection

Note: Times are indicated for 4 MHz fPERIPH

Warning: If the off time value set is superior than

the period of the PWM signal (for example 40µs off

time for a 50KHz (25µs period) PWM frequency),

then the signal output on MCOx pins selected is a

100% duty cycle signal (always at 1).

Table 48. Off time table

Note: Times are indicated for 4 MHz fPERIPH

Figure 107. Sampling clock generation block

SA3

SA2

SA1

SA0

Sampling Frequency

50.0 KHz

40.0 KHz

33.33 KHz

25.0 KHz

20.0 KHz

18.1 KHz

15.4 KHz

12.5 KHz

10 KHz

6.25 KHz

3.13 KHz

1.56 KHz

1.25 KHz

961 Hz

625 Hz

390 Hz

OT3 OT2 OT1 OT0

Off Time sen-

sorless mode

(SR=0)

(DS[3:0]=0)

Sensor Mode

(SR=1) or sam-

pling during ON

time in sensor-

less (SPLG =1

and/or DS[3:0]

bits)

2.5 µs

No minimum off

time

5 µs

7.5 µs

10 µs

12.5 µs

15 µs

17.5 µs

20 µs

22.5 µs

25 µs

27.5 µs

30 µs

32.5

µs

37.5

µs

Frequency logic

fPERIPH

Off-Time logic

SA[3:0] bits

OT[3:0] bits

Toff

Tsampling

Note: The MTC controller input frequency (

fPERIPH) is 4 MHz in this example,

MPRSR Register

MPWME Register

It can be configured to 8MHz with the XT16: XT8 bits in the MCONF register

(measurement window)

Sampling

Clock

Frequency

OFF time

The BEMF is sampled at the end of OFF time

in sensorless mode

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