PXD20RM Datasheet, PDF (1461/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

42.5.3 SSD Startup
The SSD block takes care of smooth transitions between the different steps to avoid current glitches when
the coil driven by the block (sine or cosine) changes. Single-cycle glitches in the coil drive current at
startup of the SSD flow can be avoided in the following way:
• Program the STEP bits reflecting the current position of the SM prior to the SSD flow with the
SDCPU bit still cleared.
• After programming the STEP bits enable the analog block by setting the SDCPU bit.
42.6 Application Information
This is additional information intended for use by the customer.
42.6.1 Current Flow Examples
Figure 42-13 below shows the current flow for a complete sequence of the STEP bits for
counter-clockwise movement including the recirculation time:
SINE COIL
CURRENT
+ Imax
0
_ _Imax
Recirculation
+ Imax
COSINE COIL
CURRENT
0
_ _Imax
0
1
2
3
Figure 42-13. Full Step Sequence for counter-clockwise movement
Different Examples of the current flow in the SM coils for different settings of the control bits are given
in Figure 42-14 to Figure 42-17 below:
Figure 42-14 below shows the recirculation at the beginning of STEP = 0. The cosine coil is driven in the
direction P -> M and the sine coil is recirculated against VDDM.
PXD20 Microcontroller Reference Manual, Rev. 1
42-23