MAX1021 Datasheet, PDF (22/40 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
A conversion is not performed if it is requested on a
channel or one of the channel pairs that has been con-
figured as CNVST or REF2. For channels configured as
differential pairs, the CHSEL0 bit is ignored and the two
pins are treated as a single differential channel.
Select scan mode 00 or 01 to return one result per sin-
gle-ended channel and one result per differential pair
within the selected scanning range (set by bits 2 and 1,
SCAN1 and SCAN0), plus one temperature result if
selected. Select scan mode 10 to scan a single input
channel numerous times, depending on NSCAN1 and
NSCAN0 in the ADC averaging register (Table 9).
Select scan mode 11 to return only one result from a
single channel.
Setup Register
Issue a command byte to the setup register to config-
ure the clock, reference, power-down modes, and ADC
single-ended/differential modes. Table 5 details the bits
in the setup-register command byte. Bits 5 and 4
(CKSEL1 and CKSEL0) control the clock mode, acqui-
sition and sampling, and the conversion start. Bits 3
and 2 (REFSEL1 and REFSEL0) set the device for either
internal or external reference. Bits 1 and 0 (DIFFSEL1
and DIFFSEL0) address the ADC unipolar-mode and
bipolar-mode registers and configure the analog input
channels for differential operation.
The ADC reference is always on if any of the following
conditions are true:
1)The FBGON bit is set to one in the reset register.
2)At least one DAC output is powered up and
REFSEL[1:0] (in the setup register) = 00.
3)At least one DAC is powered down through the
100kΩ to V_REF and REFSEL[1:0] = 00.
If any of the above conditions exist, the ADC reference
is always on, but there is a 188 clock-cycle delay
before temperature-sensor measurements begin, if
requested.
Table 4. Conversion Register*
BIT
NAME
—
X
CHSEL2
CHSEL1
CHSEL0
SCAN1
SCAN0
BIT
7 (MSB)
6
5
4
3
2
1
FUNCTION
Set to one to select conversion register.
Don’t care.
Analog-input channel select.
Analog-input channel select.
Analog-input channel select.
Scan-mode select.
Scan-mode select.
TEMP
0 (LSB)
Set to one to take a single temp-
erature measurement. The first
conversion result of a scan contains
temperature information.
*See below for bit details.
CHSEL2
0
0
0
0
1
1
1
1
CHSEL1
0
0
1
1
0
0
1
1
CHSEL0
0
1
0
1
0
1
0
1
SELEC T ED
C H AN N EL
(N)
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
SCAN1
0
0
1
1
SCAN0
0
1
SCAN MODE
(CHANNEL N IS SELECTED BY
BITS CHSEL2, CHSEL1, AND CHSEL0)
Scans channels 0 through N.
Scans channels N through the
highest numbered channel.
Scans channel N repeatedly. The
0
ADC averaging register sets the
number of results.
1
No scan. Converts channel N once only.
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