AMC7823_15 Datasheet, PDF (27/55 Pages) Texas Instruments – ANALOG MONITORING AND CONTROL CIRCUIT

AMC7823
www.ti.com
SLAS453F – APRIL 2005 – REVISED MARCH 2012
The bit GREF in the AMC Status/Configuration Register selects between two preset internal reference values.
When GREF = '0' (power-up default condition), the internal reference is set to 1.25V. When GREF = '1', the
internal reference is 2.5V. GREF must be cleared to '0' when the power supply is less than 5V.
When an external reference is applied, the input range is 0 to 2 × V_REF, and is not affected by the bit GREF. In
this case, ideally SREF has been set to '1' and the internal reference is disconnected. This condition is preferred
for operating the AMC7823. If SREF = '0', the external reference overrides the internal reference, provided it can
accommodate a 10kΩ load. To avoid input saturation, the external reference must not be greater than 2.5V when
the analog power supply is 5V, and must not be greater than 1.25V when the supply is 3V.
Figure 45 illustrates the ADC operation.
New ADC Conversion Trigger
Clear DAVF bit in AMC
Status/Configuration Register
Clear all ALR-n in ALR Register
Set [ADR] = [SA]
(1)
Sample
Convert
Update ADC-n TMPRY Register
No
First four channels?
Yes
Out-of-range?
No
[ADR] + 1
(2)
Drive GALR Pin Low
Yes
Set ALR-n Bit in ALR Register
No
Direct-Mode
(1)
[ADR] > [EA] ?
Yes
Update ADC-n
Data Register
Auto-Mode
No
Set DAVF bit;
Drive DAV Pin Low
Yes
(3)
Auto-Mode,
Internal Trigger only
(4)
Apply 2-ms Pulse (Low)
to Pin DAV
ADC in idle
Waiting new trigger
(1) [SA] represents the first input channel, [EA] represents the last input channel. [ADR] represents the current input
channel. [SA3:SA0] is the address of [SA]. [EA3:EA0] is the address of [EA].
(2) GALR pin goes high and bits ALR-n are cleared after new ADC Conversion trigger.
(3) After reading the ADC Data Register, bit DAVF is cleared, and the DAV pin goes high.
(4) In Auto-mode, bit DAVF is always cleared.
Figure 45. ADC Operation Flow Chart
Copyright © 2005–2012, Texas Instruments Incorporated
Product Folder Link(s): AMC7823
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