ST72141K datasheet(63/132 Pages) STMICROELECTRONICS

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ST72141K

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MOTOR CONTROLLER (Cont’d)

Direct access to the phase register is also possible

when the DAC bit in the MCRA register is set.

Table 25. DAC and MOE Bit Meaning

The polarity register is used to match the polarity

of the power drivers keeping the same control log-

ic and software. If one of the OPx bits in the MPOL

MCOx is VDD.

Each output status depends also on the momen-

tary state of the PWM, its group (odd or even), and

the peripheral state.

PWM Features

The outputs can be split in two PWM groups in or-

der to differentiate the high side and the low side

switches. This output property can be pro-

grammed using the OE[5:0] bits in the MPAR reg-

ister

Table 26. Meaning of the OE[5:0] Bits

The multiplexer directs the PWM to the upper

channel, the lower channel or both of them alter-

natively or simultaneously according to the periph-

eral state.

This means that the PWM can affect any of the up-

per or lower channels allowing the selection of the

most appropriate reference potential when free-

wheeling the motor in order to:

– Improve system efficiency

– Speed up the demagnetization phase

– Enable Back EMF zero crossing detection.

The OS[2:0] bits in the MCRB register allow the

PWM configuration to be configured for each case

as shown in Figure 41, Figure 42 and Figure 40.

This configuration depends also on the current/

voltage mode (V0C1 bit in the MCRA register) be-

cause the OS[2:0] have not the same meaning in

voltage mode and in current mode.

During demagnetization, the OS2 bit is used to

control PWM mode, and it is latched in a preload

event occurs.

The OS[1:0] bits are used to control the PWM be-

tween the D and C events.

Warning: In Voltage Mode the OS[2:0] bits have a

special configuration value: OS[2:0] = 010.

In this mode, there is NO current limitation and NO

PWM applied to active outputs. The active outputs

are always at 100% whether in demagnetization,

or normal mode.

Note about demagnetization speed-up: during

demagnetization the voltage on the winding has to

be as high as possible in order to reduce the de-

magnetization time. Software can apply a different

PWM configuration on the outputs between the C

and D events, to force the free wheeling on the ap-

propriate diodes to maximize the demagnetization

voltage.

Emergency Feature

When the NMCES pin goes low

– The tristate output buffer is put in HiZ asynchro-

nously

– The MOE bit in the MCRA register is reset

– An interrupt request is sent to the CPU if the EIM

bit in the MIMR register is set

This bit can be connected to an alarm signal from

the drivers, thermal sensor or any other security

component.

This feature functions even if the MCU oscillator is

off.

MOE bit

DAC bit

Effect on

Output

Effect on MTIM

Timer

High Z

Clock disabled

Standard run-

ning mode

Standard run-

ning mode

MPHST value

same as MPOL

value

Clock disabled

OE[5:0]

Channel group

Even channel

Odd channel

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