MAX1040 Datasheet, PDF (24/44 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
a command byte to the conversion register. Table 4
details channel selection, the four scan modes, and
how to request a temperature measurement. Start a
scan by writing to the conversion register when in clock
mode 10 or 11, or by applying a low pulse to the
CNVST pin when in clock mode 00 or 01. See Figures 6
and 7 for timing specifications for starting a scan with
CNVST.
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. For the
MAX1046–MAX1049, the CHSEL2 bit must be zero.
Channels 4–7 are invalid. Any scans or averages on
these channles can cause corrupt data.
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.
(MAX1040–MAX1043). Set to 0 on
MAX1046–MAX1049
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**
CHSEL1
CHSEL0
SELEC T ED
C H AN N EL
(N)
0
0
0
AIN0
0
0
1
AIN1
0
1
0
AIN2
0
1
1
AIN3
1
0
0
AIN4
1
0
1
AIN5
1
1
0
AIN6
1
1
1
AIN7
**Channels 4–7 are invalid on the MAX1046–MAX1049. Set
CHSEL2 bit to 0 on those devices.
SCAN1
0
0
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 ADC
1
0
averaging register sets the number of
results.
1
1
No scan. Converts channel N once only.
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