AMC7812B_14 Datasheet, PDF (47/93 Pages) Texas Instruments – 12-Bit Analog Monitoring and Control Solution with Multichannel ADC, DACs, and Temperature Sensors

AMC7812B
www.ti.com
SBAS625A – SEPTEMBER 2013 – REVISED SEPTEMBER 2013
Hysteresis
The device continuously monitors the analog input channels and temperatures. If any alarms are out of range
and the alarm is enabled, the 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 the 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 inputs, 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 device 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
CHn 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 CHn
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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