Specifications

TC35 / TC37 Hardware Interface Description
TC35_37_HD_02_V03.10 - Released Page 29 of 92 21.12.2001
synchronization between DTE and DCE upon start-up). Therefore, it is recommended to
select a fixed baudrate before using the Charge-only mode.
While the Charge-only mode is in progress, you can take advantage of the AT commands
listed in Table 5. For further instructions refer to the AT Command Set.
Table 5: AT commands available in Charge-only mode
AT command Use
AT+CALA Set alarm time
AT+CCLK Set date and time of RTC
AT^SBC Monitor charging process
Note: While charging is in progress, no battery parameters are available. To
query the battery capacity disconnect the charger.
If the charger connects externally to the host device no charging parameters
are transferred to the module. In this case, the command cannot be used.
AT^SCTM Query temperature of GSM engine
AT^SMSO Power down GSM engine
To proceed from Charge-only mode to normal operation, it is necessary to drive the ignition
line to ground. This must be implemented in your host application as described in Chapter
3.3.1.1. When the engine is in Alarm mode there is no direct way to start charging, i.e.
charging will not begin even though the charger connects to the POWER lines. See also
Chapter 3.3.5 which summarizes the various options of changing the mode of operation.
If your host application uses the SYNC pin to control a status LED as described in Chapter
3.8.2.2, please note that the LED is off while the GSM engine is in Charge-only mode.
3.2.2.4 Charger requirements
The charger must be designed to meet the following requirements:
a) Simple transformer power plug
- Output voltage: 5.5V...8V (under load)
- The charge current must be limited to 500mA
- At an output voltage of 2.8V the current must never exceed 1A
- Voltage spikes that may occur while you connect or disconnect the charger must be
limited to a maximum of 25V and must not exceed 1ms
- There must not be any capacitor on the secondary side of the power plug (avoidance of
current spikes at the beginning of charging)
b) Supplementary requirements for a) to ensure a regulated power supply
- Output voltage: 5.5V...8V
- Current limit: 500mA
- When current is switched off a voltage peak of 10V is allowed for a maximum 1ms
- When current is switched on a spike of 1.6A for 1ms is allowed
Note: To detect extreme thermal conditions while charging is in progress, connect an NTC
(10kΩ+5% @ 25°C, B=3435 Kelvin
± 3%) from ACCU_TEMP to GND.