AN2388 datasheet(28/54 Pages) STMICROELECTRONICS

28 / 54 page

Hardware design

AN2388

28/54

The comparator integrated in the L6386 is used to provide an over-current protection. The

board includes also an opto-isolation stage for separating the high voltage of the power

stage from the low voltage of the control board. Moreover, electrical insulation is also useful

to eliminate ground loop currents and for producing a noise-robust system architecture. Two

different kinds of opto-isolators have been used. Linear opto (HCNR-200) for the A/D

converter signal and switch (HCPL-2300) for the control.

Control signals come from the MDK-ST10 thanks to a 34 pin connector (standard MC

connector). This is an ST standard for all applications in motor control and has pin-out

shown in Figure 25.

The encoder signals, channels A, B, and Z (Pulse per Revolution) are filtered here with a

simple RC network. The best-fit value to set the right cut-off frequency of the low-pass filter

has to be fixed in relation with the feedback device signals. The encoder channels are

passed to the dedicated peripheral for encoder reading.

Figure 24.

Evaluation of the incremental encoder signals

Figure 25.

MC (motor control) standard connector

In order to obtain the highest noise immunity, most of the control and sensing signals are

referred to their own GND voltage. To further increase the noise immunity, it is also

suggested to use a shielded flat cable with the shield connected to the control section GND.

The delay times are neglected (<300ns)

T3input

Interrupt

Signal Conditioning

AN2388 Datasheet(PDF) 28 Page - STMicroelectronics