ADIN0
ADIN31
Self-test and
calibration
AD
REFLO
AD
REFHI
V
in
R1
R2
S4
S1 S2
S3
S5
ADC Core
ADDRx.16,9:0
ADCALR.9:0
CALR
MUX
R1 ~ 5K
R2 ~ 7K
Basic Operation
875
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
Analog To Digital Converter (ADC) Module
Figure 22-15. Self-Test and Calibration Logic
In self-test mode, a test voltage defined by the HILO bit (ADCALCR.8) is provided to the ADC core input
through a resistor (see
). To change the test source, this bit can be toggled before any single
conversion mode request. Changing this bit while a conversion is in progress
can
corrupt the results if the
source switches during the acquisition period.
Note that the switch S5 shown in
is only for the purpose of explaining the self-test sequence.
There is no physical switch.
(1)
Switches refer to
.
Table 22-3. Self-Test Reference Voltages
(1)
SELF_TEST
HILO
S1
S2
S3
S4
S5
Reference Voltage
1
0
0
1
1
0
1
AD
REFLO
via R1 || R2 connected to V
in
1
1
1
0
0
1
1
AD
REFHI
via R1 || R2 connected to V
in
0
X
0
0
0
0
1
V
in
Conversions in self-test mode are started just as they are in the normal operating mode (see
). The conversion starts according to the configuration set in the three mode control
registers (ADEVMODECR, ADG1MODECR, ADG2MODECR) and the sampling time control registers
(ADEVSAMP, ADG1SAMP, ADG2SAMP). The acquisition time for each conversion in self-test mode is
extended to twice the normal configured acquisition time. The selected reference voltage and the input
voltage from the ADINx input channel are both connected to the ADC internal sampling capacitor
throughout this extended acquisition period.
shows the self-test mode timing when the
ADREFLO is chosen as the reference voltage for the self-test mode conversion. It also assumes an
external capacitor connected to the ADC input channel.