MAX1021 Datasheet, PDF (32/40 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
Set CNVST high to begin a conversion. Sampling is
completed approximately 500ns after CNVST goes
high. After the conversion is complete, the ADC shuts
down and pulls EOC low. EOC stays low until CS or
CNVST is pulled low again. Wait until EOC goes low
before pulling CS or CNVST low. The number of CNVST
signals must equal the number of conversions request-
ed by the scan and averaging registers to correctly
update the FIFO. Wait until all conversions are com-
plete before reading the FIFO. SPI communications to
the DAC and GPIO registers are permitted during con-
version. However, coupled noise may result in degrad-
ed ADC SNR.
If averaging is turned on, multiple CNVST pulses need to
be performed before a result is written to the FIFO. Once
the proper number of conversions has been performed
to generate an averaged FIFO result (as specified to the
averaging register), the scan logic automatically switch-
es the analog input multiplexer to the next requested
channel. If a temperature measurement is programmed,
it is performed after the first rising edge of CNVST follow-
ing the command byte written to the conversion register.
The temperature-conversion result is available on DOUT
once EOC has been pulled low. Temperature results are
available in 12-bit format.
Internally Timed Acquisitions and
Conversions Using the Serial Interface
ADC Conversions in Clock Mode 10
In clock mode 10, the wake-up, acquisition, conversion,
and shutdown sequence is initiated by writing a com-
mand byte to the conversion register, and is performed
automatically using the internal oscillator. This is the
default clock mode upon power-up. See Figure 8 for
clock mode 10 timing.
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)
V_REF
100....011
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
Figure 3. Unipolar Transfer Function—Full Scale (FS) = V_REF
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)
Figure 5. Temperature Transfer Function
+255.5
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