ST7MC1 datasheet(198/308 Pages) STMICROELECTRONICS

198 / 308 page

ST7MC1/ST7MC2

198/308

MOTOR CONTROLLER (Cont’d)

10.6.9.4 Programmable Chopper

Depending on the application hardware (use of a

pulse transformer, for example), a chopper may be

needed for the PWM signal. The MREF register al-

lows the chopping frequency and mode to be pro-

grammed.

The HFE[1:0] bits program the channels on which

chopping is to be applied. The chopped PWM sig-

nal may be needed for high side switches only, low

side switches or both of them in the same time

(see Table 54).

Table 54. Chopping mode

The chopping frequency can any of the 8 values

from 100KHz to 2MHz selected by the HFRQ[2:0]

bits in the MREF register (see Table 55).

Table 55. Chopping frequency

Note: When the PCN bit = 0:

– If complementary PWM signals are not applied

(DTE bit = 0), the high and low drivers are fixed

by the MPAR register. Figure 108, Figure 114

and Figure 115 indicate where the HFE[1:0] bits

are taken into account depending on the PWM

application.

– If complementary PWM signals are applied (DTE

bit = 1), the channels are paired as explained in

“Dead Time Generator” on page 193. This

means that the high and low channels are fixed

and the HFE[1:0] bits indicate where to apply the

chopper. Figure 116 shows typical complemen-

tary PWM signals with high frequency chopping

enabled on both high and low drivers.

Figure 116. Complementary PWM signals with chopping frequency on high and low side drivers

HFE[1:0] bits

Chopping mode

HFE1

HFE0

PCN bit =0

PCN bit =1

OFF

Low channels only

Low side switches

MCO1, 3, 5

High channels only

High side switches

MCO0, 2, 4

Both Low and High

channels

Both high and low

sides

HFRQ2 HFRQ1 HFRQ0

Chopping

frequency

Fmtc = 16MHz

Fmtc = 8MHz

Chopping

frequency

Fmtc = 4MHz

100 KHz

50 KHz

200 KHz

100 KHz

400 KHz

200 KHz

500 KHz

250 KHz

800 KHz

400 KHz

1 MHz

500 KHz

1.33 MHz

666.66 MHz

2 MHz

1 MHz

Reference

Output A

Output B

Delay

Input signal

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