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SIM900D Hardware Design
Module
10K
RTC
VRTC
Core
Rechargeable
Backup Battery
Figure14: RTC supply from rechargeable battery
Module
10K
VRTC
RTC
Core
Large-capacitance
Capacitor
Figure15: RTC supply from capacitor
Li-battery backup
Coin-type Rechargeable Capacitor such as XH414H-IV01E form Seiko can be used.
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.
Figure16: Seiko XH414H-IV01E Charge Characteristic
35
SIM900D_HD_V1.02
09.04.2010
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