ADVANCE INFORMATION
3797-2·2
MA818
THREE-PHASE PULSE WIDTH MODULATION WAVEFORM GENERATOR
The MA818 PWM generator has been designed to provide
waveforms for the control of variable speed AC machines,
uninterruptible power supplies and other forms of power elec-
tronic devices which require pulse width modulation as a means
of efficient power control.
The six TTL level PWM outputs (Fig. 2) control the six
switches in a three-phase inverter bridge. This is usually via an
external isolation and amplification stage.
Rotational frequency is defined to 12 bits for high accuracy
and a zero setting is included in order to implement DC injection
braking with no software overhead. Any power waveform can be
implemented as this is user-defined in an external PROM/
EPROM. For users requiring an on-chip pre-programmed wave-
form, the functionally identical MA828 is recommended.
Information contained within the pulse width modulated
sequences controls the shape, power frequency, amplitude, and
rotational direction (as defined by the red-yellow-blue phase
sequence) of the output waveform. Parameters such as the
carrier frequency, minimum pulse width, and pulse delay time
may be defined during the initialisation of the device. The pulse
delay time (underlap) controls the delay between turning on and
off the two power switches in each output phase of the inverter
bridge, in order to accommodate variations in the turn-on and
turn-off times of families of power devices.
The MA818 is easily controlled by a microprocessor and its
fully-digital generation of PWM waveforms gives unprecedented
accuracy and temperature stability. Precision pulse shaping
capability allows optimum efficiency with any power circuitry.
The device operates as a stand-alone microprocessor periph-
eral, reading the power waveform directly from a PROM/EPROM
and requiring microprocessor intervention only when operating
parameters need to be changed.
An 8-bit multiplexed data bus is used to receive addresses and
data from the microprocessor/controller. This is a standard MOTEL
TM
bus, compatible with most microprocessors/controllers.
The MA818 is fabricated in CMOS for low power consumption.
AD
0
AD
1
AD
2
AD
3
AD
4
AD
5
AD
6
AD
7
WR* (R/W†)
RD* (DS†)
ALE* (AS†)
RST
CLK
CS
TRIP
ZPP
RPHB
YPHB
BPHB
V
SS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
40
39
38
37
36
35
34
33
32
V
DD
A
10
A
9
A
8
A
7
A
6
A
5
A
4
A
3
A
2
A
1
A
0
D
0
D
1
D
2
D
3
SET TRIP
RPHT
YPHT
BPHT
MA818
31
30
29
28
27
26
25
24
23
22
21
DC40
DG40
DP40
*
= Intel bus format
† = Motorola bus format
AD
4
AD
3
AD
2
AD
1
AD
0
V
DD
A
10
NC
A
9
A
8
A
7
39
38
37
36
35
6
5
4
3
2
1
44 43 42 41 40
AD
5
AD
6
AD
7
WR* (R/W†)
7
8
9
10
11
12
13
14
15
16
A
6
A
5
A
4
A
3
A
2
NC
A
1
A
0
D
0
D
1
D
2
FEATURES
s
Fully Digital Operation
RD* (DS†)
NC
ALE* (AS†)
RST
CLK
CS
TRIP
MA818
34
33
32
31
30
s
Interfaces with Most Microprocessors
s
Wide Power-Frequency Range
s
Carrier Frequency Selectable up to 24kHz
s
Waveform Stored in External PROM/EPROM
s
Double Edged Regular Sampling
s
Selectable Minimum Pulse Width and Underlap Time
s
DC Injection Braking
MOTEL is a registered Trademark of Intel Corp. and Motorola Corp.
17
29
18 19 20 21 22 23 24 25 26 27 28
RPHB
YPHB
BPHB
ZPP
BPHT
YPHT
RPHT
NC
SET TRIP
V
SS
D
3
HP44
Fig. 1 Pin connections – top view (not to scale)
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
