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UMTS/HSPA Module Series

UC20 Hardware Design

UC20_Hardware_Design Confidential / Released 36 / 82

3.9. RTC Backup

The RTC (Real Time Clock) can be powered by an external power source through the pin VRTC when the

module is powered down and there is no power supply for the VBAT. It is also available to charge the

battery on the VRTC when module is turned on. You can choose rechargeable battery, capacitor or

non-rechargeable battery depending on different applications.

The following figures show the various sample circuits for VRTC backup.

Module

RTC

Core

VRTC

Non-chargeable

Battery

Figure 16: RTC Supply from Non-chargeable Battery

Rechargeable

Battery

Module

RTC

Core

VRTC

Figure 17: RTC Supply from Rechargeable Battery

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