Specifications

XT55 Hardware Interface Description
Confidential / Preliminary
s
mo b i l e
XT55_hd_v00.02 Page 31 of 116 17.03.2004
3.3.1.2 Timing of the ignition process
When designing your application platform take into account that powering up the
GSM/GPRS part of the XT55 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 6: Timing of power-on process if GSM_VDDLP is not used
Figure 7: 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