AMC7812SPAPR Datasheet, PDF (47/92 Pages) Texas Instruments – 12-Bit Analog Monitoring and Control Solution with Multichannel ADC, DACs, and Temperature Sensors

AMC7812
www.ti.com
SBAS513E – JANUARY 2011 – REVISED SEPTEMBER 2013
Hysteresis
The AMC7812 continuously monitors the analog input channels and temperatures. If any of the alarms are out of
range and the alarm is enabled, its alarm bit is set ('1'). However, the alarm condition is cleared only when the
conversion result returns to a value of at least hys below the value of High Threshold Register, or hys above the
value of Low Threshold Register. The Hysteresis Registers store the value for each analog input (CH0, CH1,
CH2, and CH3) and temperature (D1, D2, and LT). hys is the value of hysteresis that is programmable: 0 LSB to
127 LSB for analog input, and 0°C to +31°C for temperatures. For the THERM-ALR bit, the hysteresis is fixed at
8°C. The hysteresis behavior is shown in Figure 98.
High Threshold
Input
Hysteresis
Low Threshold
Hysteresis
Over High Alarm
Below Low Alarm
Figure 98. Hysteresis
False Alarm Protection
As noted previously, the AMC7812 continuously monitors all analog inputs and temperatures in normal operation.
When any input is out of the specified range in N consecutive conversions, the corresponding alarm bit is set
('1'). If the input returns to the normal range before N consecutive times, the alarm bit remains clear ('0'). This
design avoids false alarms.
The number N is programmable by the CH-FALR-CT-[2:0] bits in AMC Configuration Register 1 for analog input
CH-n as shown in Table 6, or by the TEMP-FALR-CT-[1:0] bits for temperature monitors as shown in Table 7.
Table 6. Consecutive Sample Number for False Alarm Protection for CH-n
CH-FALR-CT-2
0
0
0
0
1
1
1
1
CH-FALR-CT-1
0
0
1
1
0
0
1
1
CH-FALR-CT-0
0
1
0
1
0
1
0
1
N CONSECUTIVE SAMPLES
BEFORE ALARM IS SET
1
4
8
16 (default)
32
64
128
256
Table 7. Consecutive Sample Number for False Alarm Protection for Temperature Channels
TEMP-FALR-CT-1
0
0
1
1
TEMP-FALR-CT-0
0
1
0
1
N CONSECUTIVE SAMPLES BEFORE ALARM IS SET
1
2
4 (default)
8
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