AMC7836 Datasheet, PDF (35/88 Pages) Texas Instruments – AMC7836 High-Density, 12-Bit Analog Monitor and Control Solution With Multichannel ADC, Bipolar DACs, Temperature Sensor, and GPIO Ports

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AMC7836
SLAS986C – NOVEMBER 2014 – REVISED APRIL 2016
7.3.2.4.3 ALARMIN Alarm
The AMC7836 device offers the option of using an external interrupt signal, such as the output of a comparator
as an alarm event. The GPIO0/ALARMIN pin is used as the alarm input and must be configured accordingly in
the GPIO configuration register (address 0x12). The pin is active low when configured as an alarm input.
A typical application for ALARMIN pin is to use it as a hardware interrupt that is responsible for forcing one or
more DACs to a CLEAR state. The DAC is loaded with a zero-code input and the output voltage is set according
to the operating output range, however the DAC buffer or active registers do not change (see the Digital-to-
Analog Converters (DACs) section for more details). To enable this functionality the ALARMIN pin must be
enabled as a DAC clear-alarm source in the DAC clear source 1 register (address 0x1B). Additionally the DAC
outputs to be cleared by the ALARMIN pin must be specified in the DAC clear enable registers (address 0x18
through 0x19).
In this application when the ALARMIN pin goes low, all the DACs that are set to clear in response to the
ALARMIN alarm in the DAC-clear enable registers enter a CLEAR state. When the ALARMIN pin goes back high
the DACs are reloaded with the contents of the DAC active registers which allows the DAC outputs to return to
the previous operating point without any additional commands.
7.3.2.4.4 Hysteresis
If a monitored signal is out of range and the alarm is enabled, the corresponding alarm bit is set to 1. However,
the alarm condition is cleared only when the conversion result returns either a value lower than the high
threshold register setting or higher than the low threshold register setting by the number of codes specified in the
hysteresis setting (see Figure 57). The ADC and LT hysteresis registers (address 0xA0 through 0xA4) store the
hysteresis value for the external unipolar inputs and internal temperature sensor programmable alarms. The
hysteresis is a programmable value between 0 LSB to 127 LSB for the unipolar inputs alarms and 0°C to 31°C
for the internal temperature-sensor alarms. The die thermal alarm hysteresis is fixed at 8°C.
High Threshold
Hysteresis
Low Threshold
Hysteresis
Over High Alarm
Below Low Alarm
Figure 57. Device Hysteresis
7.3.2.4.5 False-Alarm Protection
To prevent false alarms, an alarm event is only registered when the monitored signal is out of range for an N
number of consecutive conversions. If the monitored signal returns to the normal range before N consecutive
conversions, an alarm event is not issued. The false alarm factor, N, for the unipolar input and local temperature
sensor out-of-range alarms can be configured in the false alarm configuration register (address 0x11).
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