Functional Description
7-12
ADSP-214xx SHARC Processor Hardware Reference
since for the general case in double- update mode, the switching period is
given by:
Again, the values of T
AH
and T
AL
are constrained to lie between zero and
T
S
. Similar PWM signals to those illustrated in
and
can be produced on the BH and BL outputs by programming the
PWMBx
registers in a manner identical to that described for the
PWMAx
registers.
Dead Time
The second important parameter that must be set up in the initial config-
uration of the PWM block is the switching dead time. This is a short delay
time introduced between turning off one PWM signal (say
AH
) and turn-
ing on the complementary signal,
AL
. This short time delay is introduced
to permit the power switch being turned off (
AH
in this case) to completely
recover its blocking capability before the complementary switch is turned
on. This time delay prevents a potentially destructive short-circuit condi-
tion from developing across the DC link capacitor of a typical voltage
source inverter.
The 10-bit, read/write
PWMDT3–0
registers control the dead time. The dead
time, T
d
, is related to the value in the
PWMDTx
registers by:
Therefore, a PWMDT value of 0x00A (= 10), introduces a 200 ns delay
between when the PWM signal (for example
AH
) is turned off and its com-
plementary signal (
AL
) is turned on. The amount of the dead time can
d
AH
TAH
T
H
------------
1
2
---
PWMCHA
1
PWMCHA
2
PWMDT
1
PWMDT
2
–
–
+
(
)
PWMPERIOD
1
PWMPERIOD
2
+
(
)
------------------------------------------------------------------------------------------------------------------------------------------
+
=
=
T
S
PWMPERIOD
1
PWMPERIOD
2
+
(
)
t
PCLK
×
=
T
d
PWMDT
2
×
t
PCLK
×
=
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Содержание SHARC ADSP-214 Series
Страница 60: ...Contents lx ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 72: ...Notation Conventions lxxii ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 130: ...Programming Model 2 52 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 264: ...Programming Models 3 134 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 290: ...Programming Model 4 26 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 296: ...Programming Model 5 6 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 396: ...Effect Latency 7 28 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 520: ...Programming Model 10 62 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 616: ...Debug Features 14 22 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 656: ...Programming Model 15 40 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 714: ...Programming Model 19 10 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 1132: ...Register Listing A 306 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 1192: ...Index I 34 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...