Datasheet

DRV2667
www.ti.com SLOS751A –MARCH 2013–REVISED JANUARY 2014
WAVEFORM SYNTHESIS
As explained in “Waveform Synthesis Operation,” Mode 3 data is stored in sinusoidal chunks, where each chunk
consists of four bytes. The interpretation of each of these four bytes is outlined by Table 1.
Table 1. Waveform Chunk Bytes
Byte Name Description
The amplitude byte refers to the magnitude of the synthesized sinusoid. 0xFF will produce a full-scale
sinusoid, 0x80 will produce a half-scale sinusoid, and 0x00 will not produce any signal. An amplitude of 0x00
can be useful for producing timed waits or delays within the effect.
1 Amplitude
To calculate the absolute Peak voltage, use the following equation, where "Amplitude" is a single-byte integer:
Peak Voltage = Amplitude / 255 x Full Scale Peak Voltage
See “Gain Control” for the definition of the Full Scale Peak Voltage
The frequency byte adjusts the frequency of the synthesized sinusoid. The minimum frequency is 7.8125 Hz.
A value of zero is not allowed. The sinusoidal frequency is given by the following equation, where "Frequency"
2 Frequency
is a single-byte integer:
Sinusoid Frequency (Hz) = 7.8125 x Frequency
The number of sinusoidal cycles to be played by the synthesizer. Inputting the number of cycles is a
convenient way to specify the duration of a coherent sinusoid. This method will ensure that the waveform
chunk will always begin and end at zero amplitude, which avoids discontinuities. The actual duration in time
3 #Cycles (Duration)
given by this value may be calculated by the following equation, where "#Cycles" and "Frequency" are both
single-byte integers.
Duration (ms) = 1000 x #Cycles / (7.8125 x Frequency)
The Envelope byte is divided into two nibbles. The upper nibble, bits [7:4], set the ramp-up rate at the
beginning of the synthesized sinusoid, and the lower nibble, bits [3:0], set the ramp-down rate at the end of
the synthesized sinusoid. The user should note that the ramp-up time is included in the duration parameter of
the waveform, and ramp-down time is appended to the duration parameter of the waveform. As such, if a
ramp-up is used, the ramp-up time must be less than the duration time as programmed in byte 3 above. Also
note that the "Total Ramp Time" below is for a ramp to full-scale amplitude (Amplitude = 0xFF). Ramps to a
fraction of full-scale will have the same fraction of the Total Ramp Time.
Nibble Value Total Ramp Time
0 No Envelope
1 32 ms
2 64 ms
3 96 ms
4 128 ms
4 Envelope
5 160 ms
6 192 ms
7 224 ms
8 256 ms
9 512 ms
10 768 ms
11 1.024 s
12 1.28 s
13 1.536 s
14 1.792 s
15 2.048 s
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