Serial Interface - SimCom SIM5218E Hardware Design

SIM5218E Hardware Design
Figure 10: RTC supply from capacitor
Li-battery backup
Rechargeable Lithium coin cells are also small in size, but have higher capacity than the double
layer capacitors resulting in longer backup times. The coin normal voltage should be 3.0V
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 11: Seiko MS518 Charge and discharge Characteristic
Note:
Gold-capacitance backup
Some suitable coin cells are the electric double layer capacitors. They have a small physical size
(6.8 mm diameter) and a nominal capacity of 0.2 F to 0.3 F, giving hours of backup time.

3.7 Serial interface

SIM5218E provides an unbalanced asynchronous serial port. The module is designed as a DCE
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SIM5218E_HD_V1.03 11.06.2009