MAX1020_12 Datasheet, PDF (34/44 Pages) Maxim Integrated Products – 10-Bit, Multichannel ADCs/DACs with FIFO, Temperature Sensing, and GPIO Ports

10-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
Partial Reads and Partial Writes
If the first byte of an entry in the FIFO is partially read
(CS is pulled high after fewer than eight SCLK cycles),
the remaining bits are lost for that byte. The next byte of
data that is read out contains the next 8 bits. If the first
byte of an entry in the FIFO is read out fully, but the
second byte is read out partially, the rest of that byte is
lost. The remaining data in the FIFO is unaffected and
can be read out normally after taking CS low again, as
long as the 4 leading bits (normally zeros) are ignored.
If CS is pulled low before EOC goes low, a conversion
may not be completed and the FIFO data may not be
correct. Incorrect writes (pulling CS high before com-
pleting eight SCLK cycles) are ignored and the register
remains unchanged.
Applications Information
Internally Timed Acquisitions and
Conversions Using CNVST
ADC Conversions in Clock Mode 00
In clock mode 00, the wake-up, acquisition, conversion,
and shutdown sequence is initiated through CNVST
and performed automatically using the internal oscilla-
tor. Results are added to the internal FIFO to be read
out later. See Figure 6 for clock mode 00 timing after a
command byte is issued. See Table 5 for details on
programming the clock mode in the setup register.
Initiate a scan by setting CNVST low for at least 40ns
before pulling it high again. The MAX1020/MAX1022/
MAX1057/MAX1058 then wake up, scan all requested
channels, store the results in the FIFO, and shut down.
After the scan is complete, EOC is pulled low and the
results are available in the FIFO. Wait until EOC goes
low before pulling CS low to communicate with the seri-
al interface. EOC stays low until CS or CNVST is pulled
low again. A temperature-conversion result, if request-
ed, precedes all other FIFO results. Temperature
results are available in 12-bit format.
011....111
011....110
011....101
000....001
000....000
111....111
V_REF = V_REF+ - V_REF-
V_REF
V_REF
FS = V_REF / 2 + V_COM
ZS = COM
-FS = -V_REF / 2
V_REF
1 LSB = V_REF / 1024
(COM)
100....011
V_REF
100....010
100....001
100....000
-FS
-1 0 +1
+FS - 1 LSB
(COM)
INPUT VOLTAGE (LSB)
Figure 4. Bipolar Transfer Function—Full Scale (±FS) = ^±VREF / 2
111....111
111....110
111....101
FS = V_REF
FULL-SCALE
TRANSITION
1 LSB = V_REF / 1024
000....011
000....010
000....001
000....000
01 2 3
FS
INPUT VOLTAGE (LSB)
FS - 3/2 LSB
OUTPUT CODE
011....111
011....110
000....010
000....001
000....000
111....111
111....110
111....101
100....001
100....000
-256
0
TEMPERATURE (°C)
+255.5
Figure 3. Unipolar Transfer Function—Full Scale (FS) = V_REF
Figure 5. Temperature Transfer Function
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