UM0971 datasheet(17/45 Pages) STMICROELECTRONICS

17 / 45 page

UM0971

Board description

Doc ID 17701 Rev 1

17/45

Equation 2

●

R2=1500

●

R=10000

we have:

Equation 3

and:

Equation 4

If needed, further adjustments on amplified Vout voltage can be done by means of the next

block voltage divider, as shown in Figure 1 and 9.

Table 6 lists the involved jumpers and their positions for low amplitude BEMF amplification:

Moreover, please refer to Section 3 for jumper setting configurations for outputting Vout

signals through the Motor Control connector.

2.5.3

Virtual neutral (or natural) point reconstruction

When the classic analog method is used for back-EMF reading, there is a need to

reconstruct the virtual neutral point of motor windings (when star connected). To this aim,

there are different schemes. In particular, STEVAL-IHM031V1 allows implementation of

both the following (though not at the same time):

to rebuild the virtual neutral motor using three resistors and a voltage divider and filter

a voltage divider of DC bus voltage to get a proper reference voltage which follows DC

bus fluctuation

For a detailed explanation and principle schemes, please see Section 3 of application note

AN1946; Sensorless BLDC motor control and BEMF sampling methods with ST7MC.

Table 7 lists the involved jumpers and their positions for selecting how to reconstruct the

virtual neutral point:

Table 6.

Low amplitude BEMF jumper configuration

Jumper

Position

Between 1-2

2200

===

Vbias

2.5

----------------------

1.77

2R1

------------------

2.77

UM0971 Datasheet(PDF) 17 Page - STMicroelectronics

UM0971 Datasheet(HTML) 17 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

Datasheet Download

Link URL