User's Manual

TC65 Hardware Interface Description
Strictly confidential / Draft
s
TC65_HD_V00.450 Page 85 of 96 20.04.2005
7 Sample Application
Figure 38 shows a typical example of how to integrate a TC65 module into the GSM part of a
mobile application. Usage of the various host interfaces depends on the desired features of
the application.
Audio interface 1 demonstrates the balanced connection of microphone and earpiece. This
solution is particularly well suited for internal transducers. Audio interface 2 uses an
unbalanced microphone and earpiece connection typically found in headset applications.
The charging circuit is optimized for the charging stages (trickle charging and software
controlled charging) as well as the battery and charger specifications described in Section
3.5.
The PWR_IND line is an open collector that needs an external pull-up resistor which
connects to the voltage supply of the microcontroller VCC µC. Low state of the open collector
pulls the PWR_IND signal low and indicates that the TC65 module is active, high level
notifies the Power-down mode.
If the module is in Power-down mode avoid current flowing from any other source into the
module circuit, for example reverse current from high state external control lines. Therefore,
the controlling application must be designed to prevent reverse or return flow. This is not
necessary for the USB interface.
The I2C interface can be powered from an external supply or via the VEXT line of TC65. The
advantage of this solution is that when the module enters the Power-down mode, the I2C
interface is shut down as well. If you prefer to connect an I2C interface to an external power
supply, take care that the interface is shut down when the PWR_IND signal goes high in
Power-down mode.
The EMC measures are best practice recommendations. In fact, an adequate EMC strategy
for an individual application is very much determined by the overall layout and, especially,
the position of components. For example, mounting the internal acoustic transducers directly
on the PCB eliminates the need to use the ferrite beads shown in the sample schematic.
However, when connecting cables to the module’s interfaces it is strongly recommended to
add appropriate ferrite beads for reducing RF radiation.
Disclaimer
No warranty, either stated or implied, is provided on the sample schematic diagram shown in
Figure 38 and the information detailed in this section. As functionality and compliance with
national regulations depend to a great amount on the used electronic components and the
individual application layout manufacturers are required to ensure adequate design and
operating safeguards for their products using TC65 modules.