Datasheet

PIC16(L)F1784/6/7
DS41637B-page 244 Preliminary  2012 Microchip Technology Inc.
23.5.1 3-PHASE PWM
The 3-Phase mode of operation is used in 3-phase
power supply and motor drive applications configured
as three half-bridges. A half-bridge configuration con-
sists of two power driver devices in series, between
the positive power rail (high side) and negative power
rail (low side). The three outputs come from the junc-
tions between the two drivers in each half-bridge.
When the steering control selects a phase drive,
power flows from the positive rail through a high-side
power device to the load and back to the power supply
through a low-side power device.
In this mode of operation, all six PSMC outputs are
used, but only two are active at a time.
The two active outputs consist of a high-side driver
and low-side driver output.
23.5.1.1 Mode Features
• No dead-band control is available
• PWM can be steered to the following six pairs:
- PSMCxA and PSMCxD
- PSMCxA and PSMCxF
- PSMCxC and PSMCxF
- PSMCxC and PSMCxB
- PSMCxE and PSMCxB
- PSMCxE and PSMCxD
23.5.1.2 Waveform Generation
3-phase steering has a more complex waveform gen-
eration scheme than the other modes. There are sev-
eral factors which go into what waveforms are created.
The PSMC outputs are grouped into three sets of driv-
ers: one for each phase. Each phase has two associ-
ated PWM outputs: one for the high-side drive and one
for the low-side drive.
High Side drives are indicated by 1H, 2H and 3H.
Low Side drives are indicated by 1L, 2L, 3L.
Phase grouping is mapped as shown in Table 24-1.
There are six possible phase drive combinations.
Each phase drive combination activates two of the six
outputs and deactivates the other four. Phase drive is
selected with the steering control as shown in
Table 24-2.
TABLE 23-2: PHASE GROUPING
TABLE 23-3: 3-PHASE STEERING CONTROL
PSMC grouping
PSMCxA 1H
PSMCxB 1L
PSMCxC 2H
PSMCxD 2L
PSMCxE 3H
PSMCxF 3L
PSMCxSTR0 Value
(
1
)
PSMC outputs 00h 01h 02h 04h 08h 10h 20h
PSMCxA 1H inactive active active inactive inactive inactive inactive
PSMCxB 1L inactive inactive inactive inactive
active active inactive
PSMCxC 2H inactive inactive inactive
active active inactive inactive
PSMCxD 2L inactive
active inactive inactive inactive inactive active
PSMCxE 3H inactive inactive inactive inactive inactive active active
PSMCxF 3L inactive inactive active active inactive inactive inactive
Note 1: Steering for any value other than those shown will default to the output combination of the Least Significant
steering bit that is set.