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4.2 RTC Battery G1
When the board has no power the RTC IC maintains a clock using power from a small battery.
The battery holder G1 is located as shown in the diagram below. This holder will accept a CR1220 3V
battery (coin cell) or similar (BR1220). Depending on the battery used this should be capable of backing
up the operation of the PCF8523 for several months or years. It is difficult to quantify the exact time, as
this depends on factors such as the amount of time the system is powered and the initial cell capacity.
Figure 13 - Battery Location
When the battery is fitted correctly the (+)Ve terminal of the battery faces upwards.
The battery is fitted by gently pressing the cell down and against the side retaining spring clip. When
pressure is released the battery should be retained with the holder catches.
A correctly fitted battery is shown below:
Figure 14 - Correct Battery Seating
01/06/2018
Document Number
IEMAN000001
Document Title
CAN Interface pHAT User Manual
18 of 22
Document Revision
Page
R003
18 of 22
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