DSPIC30F2023 Microchip Technology Inc., DSPIC30F2023 Datasheet - Page 130

• Manufacturer Part Number: DSPIC30F2023
• Description: 28/44-pin Dspic30f1010/202x Enhanced Flash Smps 16-bit Digital Signal Controller
• Manufacturer: Microchip Technology Inc.

dsPIC30F1010/202X
FIGURE 12-17:
FIGURE 12-18:
DS70178C-page 128
Negative dead time
Positive dead time
No dead time
9
PWML
PWMH
PWMH
PWMH
PWML
PWML
0
DTRx
DUAL DEAD-TIME
WAVEFORMS
DEAD-TIME INSERTION (PWM OUTPUT SIGNAL TIMING MAY BE DELAYED)
1
ALTDTRx
2
3
4
1
Preliminary
4
5
12.14.3
The amount of dead time provided by each dead-time
unit is selected by specifying a 12-bit unsigned value in
the DTRx registers. The 12-bit dead-time counters
clock at four times the instruction execution rate. The
Least Significant one bit of the dead-time value are
processed by the Fine Adjust PWM module.
Table 12-3 shows example dead-time ranges as a
function of the device operating frequency.
TABLE 12-3:
12.14.4
Figure 12-18 shows how the dead-time insertion for
complementary signals is accomplished.
12.14.5
For small PWM duty cycles, the ratio of dead time to the
active PWM time may become large. In this case, the
inserted dead time introduces distortion into wave-
forms produced by the PWM module. The user can
ensure that dead-time distortion is minimized by keep-
ing the PWM duty cycle at least three times larger than
the dead time.
A similar effect occurs for duty cycles at or near 100%.
The maximum duty cycle used in the application should
be chosen such that the minimum inactive time of the
signal is at least three times larger than the dead time.
MIPS
30
20
6
DEAD-TIME RANGES
DEAD-TIME INSERTION TIMING
DEAD-TIME DISTORTION
7
Resolution
EXAMPLE DEAD-TIME
RANGES
4.16 ns
6.25 ns
© 2006 Microchip Technology Inc.
8
Dead-Time Range
CLOCK
PTMR
DEAD-TIME VALUE
<10:4>
DUTY CYCLE REG
<15:4>
RAW PWMH
RAW PWML
PWMH OUTPUT
PWML OUTPUT
0-17.03 µsec
0-25.59 µsec