EM3027
9.2
Low Supply Detection
The supply voltage level is monitored periodically versus
Vlow1 and Vlow2 levels. The monitoring rate is one
second. When the voltage monitoring is running, a higher
current consumption for few milliseconds occurs.
To leave the VLOW1 status, the supply voltage must be
increased above the Vlow1 level and a ‘0’ value must be
written into the VLOW1 status bit via the serial interface.
When the supply voltage drops below the Vlow2 level,
the VLOW2 status bit is set by the voltage monitoring
system.
At the power-up of the device, as long as the supply
voltage stays below Vlow2, the monitoring rate is
accelerated. To enable normal operation, the chip must
be supplied with a voltage above Vlow2, to enable the
readout of initialization data from EEPROM and to stop
the higher current consumption.
The VLOW2 status bit disables the read out of the
EEPROM.
When the supply voltage drops from the normal range
(from 2.1V to 5.5V) below Vlow1, the VLOW1 status bit is
set to ‘1’ by the voltage monitoring system.
To leave the VLOW2 status, the supply voltage must be
increased above the Vlow2 level and a ‘0’ value must be
written into the VLOW2 status bit via the serial interface.
When bit VLOW1 is at ‘1’, the thermometer is disabled
and the automatic computation of the thermal
compensation value (COMP_val) for frequency
correction is inhibited. In this case, the last computed
compensation value is used.
Below Vlow2 level, device functionality is not guaranteed
and register contents can be corrupted. Therefore, if
VLOW2 status bit is set, it is recommended to perform
system reset by writing of ‘1’ into SYSRes bit in RstCtrl
page and afterwards update content of Watch, Alarm and
Timer registers.
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Copyright 2013, EM Microelectronic-Marin SA
3027-DS.doc, Version 8.0, 25-Jan-13
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