ZSSC3122 Datasheet, PDF (38/64 Pages) List of Unclassifed Manufacturers – Low Voltage Capacitive Sensor Signal Conditioner

ZSSC3122 Datasheet
3.8 Alarm Output
The alarm output can be used to monitor whether a corrected capacitance reading has exceeded or fallen below
pre-programmed values. The alarm can be used to drive an open-drain load connected to VDD, as demonstrated
in section 7.2, or it can function as a full push-pull driver. If a high voltage application is required, external devices
can be controlled with the Alarm pins, as demonstrated in section 7.3.
The two alarm outputs can be used at the same time, and these alarms can be used in combination with any of
the other three modes; I²C™, SPI, or PDM.
Note: When both PMD_C and PDM_T are selected only Alarm_High is available (see section 3.5).
The alarm outputs are updated when a conversion cycle is completed. The alarm outputs can be used in both
Update Mode and Sleep Mode, but if Sleep Mode is used, I²C™ or SPI must also be used to control the measure-
ments (see section 3.3).
3.8.1 Alarm Registers
Four registers are associated with the alarm functions: Alarm_High_On, Alarm_High_Off, Alarm_Low_On, and
Alarm_Low_Off (see Table 5.1 for EEPROM addresses). Each of these four registers is a 14-bit value that deter-
mines where the alarms turn on or off. The two high alarm registers form the output with hysteresis for the
Alarm_High pin, and the two low alarm registers form the output with hysteresis for the Alarm_Low pin. Each of
the two alarm pins can be configured independently using Alarm_Low_Cfg and Alarm_High_Cfg located in
EEPROM word Cust_Config (see Table 5.5 for bit assignments).
Note: If two high alarms or two low alarms are needed, see section 3.8.4.
3.8.2 Alarm Operation
As shown in Figure 3.14, the Alarm_High_On register determines where the high alarm trip point is and the
Alarm_High_Off register determines where the high alarm turns off if the high alarm has been activated. The high
alarm hysteresis value is equal to Alarm_High_On – Alarm_High_Off. The same is true for the low alarm where
Alarm_Low_On is the low alarm trip point with Alarm_Low_Off determining the alarm shut off point. The low alarm
hysteresis value is equal to Alarm_Low_Off – Alarm_Low_On. Figure 3.15 shows output operation flowcharts for
both the Alarm_High and Alarm_Low pins.
© 2016 Integrated Device Technology, Inc.
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January 25, 2016