ST7MC1 datasheet(145/308 Pages) STMICROELECTRONICS

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ST7MC1/ST7MC2

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MOTOR CONTROLLER (Cont’d)

10.6.5 Functional Description

The MTC can be split into five main parts as

shown in the simplified block diagram in Figure 77.

Each of these parts may be configured for different

purposes:

■ INPUT DETECTION BLOCK with a comparator,

an input multiplexer and an incremental encoder

interface, which may work as:

– A BEMF zero-crossing detector

– A Speed Sensor Interface

■ The DELAY MANAGER with an 8/16-bit timer

and an 8x8 bit multiplier, which may work as a:

– 8-bit delay manager

– Speed Measurement unit

■ The

PWM

MANAGER,

including

measurement

window

generator,

mode

selector and a current comparator.

■ The CHANNEL MANAGER with the PWM

multiplexer, polarity programming, deadtime

insertion

and

high

frequency

chopping

capability and emergency HiZ configuration

input.

■ The THREE-PHASE PWM GENERATOR with

12-bit

free-running

counter

and

repetition

counter.

10.6.6 Input Detection Block

This block can operate in Position sensor mode, in

sensorless mode or in Speed Sensor mode. The

mode is selected via the SR bit in the MCRA reg-

ister and the TES[1:0] bits in MPAR register (refer

to Table 35 for set-up information). The block dia-

gram is shown in Figure 78 for the Position Sen-

sor/Sensorless modes (TES[1:0] = 00) and in Fig-

ure 88 for the Speed Sensor mode (TES[1:0] = 01,

10, 11).

10.6.6.1 Input Pins

The MCIA, MCIB and MCIC input pins can be

used as analog or as digital pins.

– In sensorless mode, the analog inputs are used

to measure the BEMF zero crossing and to de-

tect the end of demagnetization if required.

– In sensor mode, the analog inputs are used to

get the Hall sensor information.

– In speed sensor mode (e.g. tachogenerator), the

inputs are used as digital pins. When using an

AC tachogenerator, a small external circuit may

be needed to convert the incoming signal into a

square wave signal which can be treated by the

MTC.

Due to the presence of diodes, these pins can per-

manently support an input current of 5mA. In sen-

sorless mode, this feature enables the inputs to be

connected to each motor phase through a single

resistor.

A multiplexer, programmed by the IS[1:0] bits in

the MPHST register selects the input pins and

connects them to the control logic in either sensor-

less or tachogenerator mode. In encoder mode, it

is mandatory to connect sensor digital outputs to

the MCIA and MCIB pins.

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