71M6521 Demo Board User’s Manual
Revision 2.18
© 2005-2009 TERIDIAN Semiconductor Corporation
Page: 65 of 111
Figure 2-16: RESET Switch Supplied by VBAT
Figure 2-17: RESET Switch with Multiple Supplies
2.3.8 OPERATION WITH BATTERIES
Some types of meters are equipped with batteries, mostly to support TOU (time-of-use) functions. In these
meters the battery maintains the oscillator circuit and the RTC, when board power is not present.
Many meter manufacturers assemble the meter PCB with the 71M6521 IC and the other electronic
components first and then join the meter PCB with the meter enclosure, sensors and other main components
separately at a later production step. Typically, final test (ATE), and calibration is performed after this second
step.
Programming of the flash memory and insertion of a battery may happen at intermediate steps.
To prevent battery drainage, it is essential that the code is written to permit transition to sleep mode
immediately after the battery is inserted into the meter PCB.
R
1
RESET
71M6521
DGND
V3P3D
R
2
VBAT
Reset
Switch
1k
Ω
0.1µF
10k
Ω
R
1
RESET
71M6521
DGND
V3P3D
VBAT
Reset
Switch
1k
Ω
0.1µF
10k
Ω
mission,
brownout modes
LCD,
sleep
modes
