Datasheet

MAX11618–MAX11621/MAX11624/MAX11625
10-Bit, 300ksps ADCs
with FIFO and Internal Reference
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Conversion Register
Select active analog input channels per scan and scan
modes by writing to the conversion register. Table 2
details channel selection and the four scan modes.
Request 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.
A conversion is not performed if it is requested on a
channel that has been configured as CNVST. Do not
request conversions on channels 8–15 on the
MAX11618–MAX11621. Set CHSEL3:CHSEL0 to the
lower channel’s binary values.
Select scan mode 00 or 01 to return one result per sin-
gle-ended channel within the requested range. Select
scan mode 10 to scan a single input channel numerous
times, depending on NSCAN1 and NSCAN0 in the
averaging register (Table 4). Select scan mode 11 to
return only one result from a single channel.
Setup Register
Write a byte to the setup register to configure the clock,
reference, and power-down modes. Table 3 details the
bits in the setup register. Bits 5 and 4 (CKSEL1 and
CKSEL0) control the clock mode, acquisition and sam-
pling, and the conversion start. Bits 3 and 2 (REFSEL1
and REFSEL0) control internal or external reference use.
Averaging Register
Write to the averaging register to configure the ADC to
average up to 32 samples for each requested result,
and to independently control the number of results
requested for single-channel scans.
Table 2 details the four scan modes available in the
conversion register. All four scan modes allow averag-
ing as long as the AVGON bit, bit 4 in the averaging
register, is set to 1. Select scan mode 10 to scan the
same channel multiple times. Clock mode 11 disables
averaging.
Reset Register
Write to the reset register (as shown in Table 5) to clear
the FIFO or to reset all registers to their default states.
Set the RESET bit to 1 to reset the FIFO. Set the reset
bit to zero to return the MAX11618–MAX11621/
MAX11624/MAX11625 to the default power-up state.
BIT
NAME
BIT FUNCTION
— 7 (MSB) Set to 1 to select conversion register.
CHSEL3 6 Analog input channel select.
CHSEL2 5 Analog input channel select.
CHSEL1 4 Analog input channel select.
CHSEL0 3 Analog input channel select.
SCAN1 2 Scan mode select.
SCAN0 1 Scan mode select.
— 0 (LSB) Don’t care.
Table 2. Conversion Register*
* See below for bit details.
CHSEL3 CHSEL2 CHSEL1 CHSEL0
SELECTED
CHANNEL (N)
0 0 0 0 AIN0
0 0 0 1 AIN1
0 0 1 0 AIN2
0 0 1 1 AIN3
0 1 0 0 AIN4
0 1 0 1 AIN5
0 1 1 0 AIN6
0 1 1 1 AIN7
1 0 0 0 AIN8
1 0 0 1 AIN9
1 0 1 0 AIN10
1 0 1 1 AIN11
1 1 0 0 AIN12
1 1 0 1 AIN13
1 1 1 0 AIN14
1 1 1 1 AIN15
SCAN1 SCAN0
SCAN MODE (CHANNEL N IS
SELECTED BY BITS CHSEL3–CHSEL0)
0 0 Scans channels 0 through N.
01
Scans channels N through the highest
numbered channel.
10
S cans channel N r ep eated l y. The aver ag i ng
r eg i ster sets the num b er of r esul ts.
1 1 No scan. Converts channel N once only.