User's Manual
Table Of Contents
- Document History
- Introduction
- Product Concept
- Application Interface
- Operating Modes
- Power Supply
- Power Up / Power Down Scenarios
- Automatic GPRS Multislot Class Change
- Charging Control
- Summary of State Transitions (Except SLEEP Mode)
- RTC Backup
- SIM Interface
- Serial Interface ASC0
- Serial Interface ASC1
- USB Interface
- I2C Interface
- Audio Interfaces
- Control Signals
- Antenna Interface
- Electrical, Reliability and Radio Characteristics
- Mechanics
- Sample Application
- Reference Approval
- Appendix
TC63 Hardware Interface Description
Strictly confidential / Draft
s
TC63_HD_V00.432 Page 55 of 97 11.05.2005
3.13.2.3 Line Input Configuration with OpAmp
Figure 20 shows an example of how to connect an opamp into the microphone circuit.
GSM module
R
A
V
Bias
C
K
AGND
MICNx
MICPx
VMIC
R
A
C
K
~
R
VMIC
C
F
R
A
= typ. 47k
R
VMIC
= 470Ohm
C
k
= typ. 100nF
C
F
= typ. 22µF
V
MIC
= typ. 2.5V
V
bias
= typ. ½ V
MIC
= 1.25V
Figure 20: Line input configuration with OpAmp
The AC source (e.g. an opamp) and its reference potential have to be AC coupled to the
MICPx resp. MICNx input terminals. The voltage divider between VMIC and AGND is
necessary to bias the input amplifier. MICNx is automatically self biased to the MICPx DC
level.
The VMIC voltage should be filtered if gains larger than 20dB are used. The filter can be
attached as a simple first order RC-network (R
VMIC
and C
F
). If a high input level and a lower
gain are applied the filter is not necessary.
If desired, MICNx via C
K
can also be connected to the inverse output of the AC source
instead of connecting it to the reference potential for differential line input.