ST72141K2 datasheet(50/132 Pages) STMICROELECTRONICS

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ST72141K

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MOTOR CONTROLLER (Cont’d)

Sensor Mode

In sensor mode, the rotor position information is

given to the peripheral by means of logical data on

the three inputs MCIA, MCIB and MCIC.

For each step one of these three inputs is selected

(IS[1:0] bits in register MPHST) in order to detect

the Z event.

In this case Demagnetization has no meaning and

the relevant features such as the special PWM

configuration, DS or DH management, 20-µs filter;

are not available (see Table 14).

For this configuration the rotor detection doesn’t

need a particular phase configuration to validate

the measurement and a Z event can be read from

any detection window. A fixed sampling frequency

(800 kHz) is used, that means the Z event and po-

sition sensoring is more precise than it is in sen-

sorless mode.

The minimum off time for current control PWM is

also reduced to 1.25

µs.

Procedure for reading sensor inputs in Direct

Access mode: In Direct Access mode, the periph-

eral clock is disabled as shown in Table 25. As the

data present on the selected input is synchronized

by a 800 kHz clock, the sensor can’t be read di-

rectly (the value is latched). To read the sensor

data the following steps have to be performed:

1. Select the appropriate MCIx input pin by means

of the IS[1:0] bits in the MPHST register

2. Switch from direct access mode to indirect

access mode in order to latch the sensor data

(DAC bit in MCRA register).

3. Switch back to direct access mode.

4. Read the comparator output (HST bit in the

MIMR register)

Table 14. Sensor mode selection

SR bit

Mode

OS2 bit use

Event detection

sampling clock

Filtering

Behaviour of the output

PWM

Sensors not

used

Enabled

D: Clock 1.25

µs

Z: SA&OT config.

µs after C for D event

µs after D for Z event

“Before D” behaviour

& “after D” behaviour

Sensors

used

Disabled

Z: Clock 1.25

µs20µs after C for Z event

Only “after D” behaviour

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