User's Manual
Table Of Contents
- Contents
- Figures
- Tables
- Document history
- Introduction
- Product concept
- GSM application interface
- GSM/GPRS operating modes
- Power supply
- Power up / down scenarios
- Automatic GPRS Multislot Class change
- Charging control of the GSM part
- Power saving
- Summary of state transitions (except SLEEP mode)
- RTC backup for GSM part of XT55/56
- Serial interfaces of the XT55/56 GSM part
- Audio interfaces
- SIM interface
- Control signals
- GPS application interface
- GSM and GPS antenna interfaces
- Electrical, reliability and radio characteristics
- Mechanics
- Reference approval
- Example applications
- List of parts and accessories
XT55/56 Hardware Interface Description
Confidential / Released
s
XT55/56_hd_v02.06a Page 32 of 125 17.12.2004
3.3.1.2 Timing of the ignition process
When designing your application platform take into account that powering up the GSM part of
the XT55/56 module requires the following steps.
• The ignition line cannot be operated until V
GSM_BATT+
passes the level of 3.0V.
• The ignition line shall not be operated earlier than 10ms after the last falling edge of
GSM_VDD.
• 10ms after V
GSM_BATT+
has reached 3.0V the ignition line can be switched low. The
duration of the falling edge must not exceed 1ms.
• Another 100ms are required to power up the module.
• Ensure that V
GSM_BATT+
does not fall below 3.0V while the ignition line is driven. Otherwise
the module cannot be activated.
• If the GSM_VDDLP line is fed from an external power supply as explained in Chapter 3.8,
the GSM_IGT line is HiZ before the rising edge of GSM_BATT+.
Figure 4: Timing of power-on process if GSM_VDDLP is not used
Figure 5: Timing of power-on process if GSM_VDDLP is fed from external source
3.0V
0V
GSM_BATT+
min. 100ms
max. 1ms
10ms
GSM_IGT
HiZ
HiZ
3.0V
0V
min. 100ms
max. 1ms
10ms
HiZ
HiZ
GSM_BATT+
GSM_IGT