User's Manual
Table Of Contents
- Contents
- Table Index
- Figure Index
- 0. Revision history
- 1. Introduction
- 2. Product concept
- 3. Application interface
- 3.1. Pin of module
- 3.2. Operating modes
- 3.3. Power supply
- 3.4. Power on and down scenarios
- 3.5. Charge interface
- 3.6. Power saving
- 3.7. Summary of state transition
- 3.8. RTC backup
- 3.9. Serial interfaces
- 3.10. Audio interfaces
- 3.11. SIM card interface
- 3.12. SD card interface
- 3.13. PCM interface
- 3.14. ADC
- 3.15. Behaviors of the RI
- 3.16. Network status indication
- 3.17. Operating status indication
- 4. Antenna interface
- 5. Electrical, reliability and radio characteristics
- 6. Mechanical dimensions
- 7. Storage and manufacturing
- Appendix A: GPRS coding schemes
- Appendix B: GPRS multi-slot classes
M50 Hardware Design
M50_HD_V2.0 - 40 -
3.8. RTC backup
The RTC (Real Time Clock) can be supplied by an external capacitor or battery (rechargeable or
non-chargeable) through the pin VRTC. A 1.5K resistor has been integrated in the module for
current limiting. A coin-cell battery or a super-cap can be used to backup power supply for RTC.
The following figures show various sample circuits for RTC backup.
Module
RTC Core
1.5K
VRTC
Non-chargeable
Backup Battery
Figure 14:
RTC supply from non-chargeable battery
VRTC
Rechargeable
Backup Battery
Module
RTC Core
1.5K
Figure 15: RTC supply from rechargeable battery
VRTC
Large Capacitance
Capacitor
Module
RTC Core
1.5K
Figure 16:
RTC supply from capacitor
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