AN1524 Freescale Semiconductor / Motorola, AN1524 Datasheet - Page 7

• Manufacturer Part Number: AN1524
• Description: AC Motor Drive Using Integrated Power Stage
• Manufacturer: Freescale Semiconductor / Motorola

The demo board does not provide any dead time. The
microcontroller can provide accurate digitally generated dead
time far better than an analog circuit. Appropriate PWM
signals are illustrated in Figure 10.
2 s. Less than 2 s of dead time will allow some shoot
through current during switching, resulting in higher switching
MOTOROLA
WB
WT
UB
The PWM signals should be center aligned with dead time.
UT
VB
The recommended dead time for the demo board is at least
VT
CN7
+ 5 V
GND
BRK
I/O1
I/O2
I/O3
NC
Wb
Ub
Vb
Wt
Vo
To
Ut
Vt
Io
+ 5 V
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
2 s
J4
Figure 10. PWM Timing
+ 5 V
IO
VO
TO
Freescale Semiconductor, Inc.
For More Information On This Product,
R3–R9
4.7 k
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Figure 9. Input Logic
10
11
losses. Inadequate dead time may also result in damage to the
power transistors.
PLD Programming
This PLD provides only two basic essential functions,
half–bridge lockout and a master enable. A half–bridge
lockout ensures that both upper and lower transistors are not
simultaneously turned on. The master enable function
enables or disables all six PWM signals according to the
position of SW1 (U2 pin I0).
signals. Therefore jumper J1 should be positioned to
configure the input resistors as pull downs. The three general
purpose I/O pins are programmed for compatibility with the
HC16Y1 development system. Connector CN7 pin 6 (I/O3) is
connected to the active low fault pin of the development
system. It is set high to enable the PWM signals. The other two
I/O pins are tri–stated. The logic equations for the standard
PLD were compiled using ABLE. The PLDs were
5
6
7
8
9
S1
The demo board is shipped with a preprogrammed PLD.
The standard PLD is programmed for active high logic
+ 5 V
I3
I4
I5
NC
I6
I7
I8
R10
4.7 k
I2
I9
4
12
I10
I1
3
13
GND
I0
2
14
22V10
NC
NC
1
15
+ 5 V
V CC I/O9 I/O8
I11
16
28
I/O0
27
17
I/O1
26
18
I/O7
I/O6
I/O5
I/O4
I/O3
I/O2
NC
U2
25
24
23
22
21
20
19
AN1524
UT
VT
WT
UB
VB
WB
BRK
OV
OC
7