em3027 EM Microelectronic, em3027 Datasheet - Page 20

• Manufacturer Part Number: em3027
• Description: Real-time Clock With I2c Or Spi Interface, Crystal Temperature Compensation, Battery Switchover And Trickle Charger
• Manufacturer: EM Microelectronic

By setting of a trickle charger bit in register EECtrl a resistor can be inserted between V
and V
voltage. In this way a
Back
High
rechargeable battery or a super-cap can be charged from the V
voltage, as long as V
> V
. More than one resistor
CC
CC
Back
can be selected or all.
There are 4 selectable resistors with a nominal value of 80kΩ, 20kΩ, 5kΩ and 1.5kΩ can be set by EEctrl bits.
9.2
Low Supply Detection
The supply voltage level is monitored periodically versus Vlow1 and Vlow2 levels. The monitoring rate is defined by the
ThPer bit and is the same as the temperature monitoring rate. When the voltage monitoring is running a higher current
consumption for few milliseconds occurs.
At the power-up of the device, as long as the supply voltage stays below Vlow2, the monitoring rate is speeded up. It is
necessary to power up at a level above Vlow2 in order to be able to read out initialization data from EEPROM and to leave
the fast monitoring rate with higher current consumption. (See chapter 8.1)
When the voltage drops below Vlow1 then the VLOW1 status bit is set to ‘1’. It is only possible to clear VLOW1 by
increasing the supply voltage above Vlow1 and then writing ‘0’ into the VLOW1 status bit.
When bit VLOW1 is at ‘1’, the thermometer is disabled and the automatic computation of compensation value (COMP_val)
for frequency correction is inhibited. In this case the last computed compensation value is used.
The device continues to work until the supply voltage drops below the limit Vlow2 which is the minimum supply voltage of
the device with EEPROM read out function.
When bit VLOW2 is set, it can only be reset by increasing the supply above the level Vlow2 and then writing ‘0’ into the
VLOW2 status bit.
Below the Vlow2 level the EEPROM read out is disabled and the device functionality is not guaranteed.
Copyright © 2008, EM Microelectronic-Marin SA
20
www.emmicroelectronic.com
07/08 – rev B