Sim800 hardware design v1.05
Table Of Contents
- Version History
- 1. Introduction
- 2. SIM800 Overview
- 3. Package Information
- 4. Application Interface
- 4.1. Power Supply
- 4.2. Power on/down SIM800
- 4.3. Power Saving Mode
- 4.4. RTC Backup
- 4.5. Serial Port and USB Interface
- 4.6. RI Behaviors
- 4.7. Audio Interfaces
- 4.8. Bluetooth
- 4.9. SIM Card Interface
- 4.10. PCM Interface
- 4.11. Keypad Interface
- 4.12. I2C BUS
- 4.13. General Purpose Input/Output (GPIO)
- 4.14. ADC
- 4.15. PWM
- 4.16. Network Status Indication
- 4.17. Operating Status Indication
- 4.18. KPLED
- 4.19. RF Synchronization Signal
- 4.20. Antenna Interface
- 5. PCB Layout
- 6. Electrical, Reliability and Radio Characteristics
- 6.1 Absolute Maximum Ratings
- 6.2 Recommended Operating Conditions
- 6.3 Digital Interface Characteristics
- 6.4 SIM Card Interface Characteristics
- 6.5 SIM_VDD Characteristics
- 6.6 VDD_EXT Characteristics
- 6.7 VRTC Characteristics
- 6.8 Current Consumption (VBAT=4V)
- 6.9 Electro-Static Discharge
- 6.10 Radio Characteristics
- 6.11 Module RF Receive Sensitivity
- 6.12 Module Operating Frequencies
- 7. Manufacturing
- 8. Appendix
Smart Machine Smart Decision
4.4. RTC Backup
VRTC is an input pin when the VBAT is not supplied by external power. When the VBAT power supply is in
present and the backup battery is in low voltage state, VRTC can charge the backup battery. The RTC power
supply of module can be provided by an external capacitor or a battery (non-chargeable or rechargeable) through
the VRTC. The following figures show various reference circuits for RTC back up.
z External capacitor backup
Figure 16: RTC supply from capacitor
z Non-chargeable battery backup
Figure 17: RTC supply from non-chargeable battery
z Rechargeable battery backup
Figure 18: RTC supply from rechargeable battery
SIM800_Hardware Design_V1.05 28 2014-03-25