MA838 Datasheet, PDF (11/13 Pages) Zarlink Semiconductor Inc – SINGLE PHASE PULSE WIDTH MODULATION WAVEFORM GENERATOR

MA838
1. Setting the power frequency
The power frequency, f_POWER, can be selected to 12-bit
accuracy (i.e 4096 equal steps) from 0Hz to f_RANGE as defined
in the initialisation register. In this case, with f_RANGE = 250Hz,
the power frequency can be adjusted in increments of 0·06Hz.
f_POWER
=^fRANGE
4096
x
pfs
pfs = ^{fPOWER x 4096} = ^{100 x 4096} = 1638·4
f_RANGE
250
We can only have pfs as an integer, so if we assign pfs =
1638 this gives f_POWER = 99.97 Hz.The 12-bit binary equivalent
of this value gives a PFS word of 011001100110 in temporary
registers R0 and R1.
2. Setting overmodulation, output inhibit
Overmodulation is not required therefore OM = 0.
Output inhibit should be inactive (i e., the outputs should be
active), therefore INH= 1.
These bits are all set in temporary register R1.
3. Setting the power waveform amplitude
A
A_POWER =
x 100%
225
A = ^{APOWER x 255} = ^{80 3x 255} = 204
100
100
The 8-bit binary equivalent of this value gives an AMP word
of 11001100 in temporary register R2. The data which must be
programmed into the three temporary registers R0, R1 and R2
(for transfer into the control register) in order to achieve the
parameters in the example given, is shown in Fig. 16.
Fig. 16
10
Fig. 17 Typical MA838 programming routine