SIM Tech SimCom SIM340 Hardware Design page 33

SIM340 Hardware Design
MODULE
10K
VRTC
RTC
Core
Large-capacitance
Capacitor
Figure 14: RTC supply from capacitor
Li-battery backup
Rechargeable Lithium coin cells such as the TC614 from Maxell, or the TS621 from Seiko, are
also small in size, but have higher capacity than the double layer capacitors resulting in longer
backup times.
Typical charge curves for each cell type are shown in following figures. Note that the rechargeable
Lithium type coin cells generally come pre-charged from the vendor.
Figure 15: Panasonic EECEMOE204A Charge Characteristic
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SIM340_HD_V3.09 18.03.2009