User Manual
Table Of Contents
- 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 / Preliminary
s
XT55/56_hd_v02.96 Page 47 of 125 18.08.2005
4.3
4.2
3.8
Voltage
3.4
3.0
Constant current
t
OFF
= 100 ms
t
ON
= 100 ms
Time
100ms
2 ... 0.1s
100ms
0.1 ... 2s
End of
charging
Figure 10: Charging process
Note: Do not
connect the charger to the GSM_BATT+ lines. Only the charger input of the
external charging circuit is intended as input for charging current! The
GSM_POWER pin of XT55/56 is the input only for indicating a connected charger!
The battery manufacturer must guarantee that the battery complies with the
described charging technique.
What to do if software controlled charging does not start up?
If trickle charging fails to raise the battery voltage to 3.2V within 60 minutes +
10%, processor
controlled charging does not begin. To start fast charging you can do one of the following:
• Once the voltage has risen above its minimum of 3V, you can try to start software
controlled charging by pulling the GSM_IGT line to ground.
• If the voltage is still below 3V, driving the GSM_IGT line to ground switches the timer off.
Without the timer running, the GSM part of the XT55/56 module will not proceed to
software controlled charging. To restart the timer you are required to shortly disconnect
and reconnect the charger.