AMC7823_15 Datasheet, PDF (26/55 Pages) Texas Instruments – ANALOG MONITORING AND CONTROL CIRCUIT

AMC7823
SLAS453F – APRIL 2005 – REVISED MARCH 2012
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SS
WRITE ADC
CONTROL Register
1st Internal
Trigger
MOSI
WRITE ADC
CONTROL Register
2nd Internal
Trigger
DAV
SS
WRITE ADC
CONTROL Register
Internal Trigger
MOSI
DAV
2ms
1st Conversions,
2nd Conversions,
[SA3:SA0] to [EA3:EA0] [SA3:SA0] to [EA3:EA0]
Figure 42. Internal Trigger, Direct-Mode
Rising Edge
Starts Conversions
CONVERT
1st Trigger
1st Round of
2nd Round of
Conversions,
Conversions,
[SA3:SA0] to [EA3:EA0] [SA3:SA0] to [EA3:EA0]
Figure 43. Internal Trigger, Auto-Mode
2nd Trigger
3rd Trigger
DAV
1st Conversions, of
2nd Conversions,
3rd Conversions,
Analog Inputs, From _{[SA3:SA0] to [EA3:EA0] [SA3:SA0] to [EA3:EA0]}
[SA3:SA0] to [EA3:EA0]
Figure 44. External Trigger
Analog Input Out-of-Range Detection (see Analog Input Out-of-Range Alarm Section)
The first four analog inputs of the group defined by the bits [SA3:SA0] and [EA3:EA0] are implemented with out-
of-range detection. When an input is out of the preset range, the corresponding alarm flag, bit ALR-n of the ALR
(Alarm) Register is set. If any of the four inputs are out of range, the global out-of-range pin GALR goes low.
Four GPIO pins (GPIO-0, GPIO-1, GPIO-2 and GPIO-3) can be configured as out-of-range indicators for each of
the first four analog inputs. See the Analog Input Out-of-Range Alarm and Digital I/O sections for more details.
Full-Scale Range of Analog Input
The full-scale range of the analog input is 2 × V_REF, but must not exceed the supply value AV_DD. Input saturation
can occur if the analog input exceeds this value.
The internal reference or an externally applied reference may be used as V_REF. The bit SREF in the AMC
Status/Configuration Register controls the selection of the internal reference. When SREF = '0' (power-up default
condition), the internal reference is selected and is internally applied through a 10kΩ resistor to pin 21. When
SREF = '1', the internal reference is disconnected from pin 21, and an external reference may be applied. See
Figure 48.
Table 4 shows the configuration of the ADC input range.
BIT
GREF
0
1
Don't
care
BIT
SREF
0
0
1
Table 4. Configuration of ADC Input Range
ADC INPUT
RANGE
0 to 2.5V
0 to 5V
0 to 2 × V_REF
DESCRIPTION
Internal reference, 1.25V
Internal reference, 2.5V, AV_DD = 5V only
External reference V_REF. 2 × V_REF must not be greater than AV_DD.
Set SREF = 1 when applying external reference.
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