CC864-DUAL Hardware User Guide
1vv0300791 Rev 4.4 – 2011-01-26
Reproduction forbidden without Telit Communications S.p.A’s. written authorization - All Rights Reserved.
Page 43 of 63
3.9.2.
Output lines (Speaker)
We suggest driving the load differentially from both output drivers, thus the output
swing will double and the need for the output coupling capacitor avoided.
If a
particular OEM application needs a
Single Ended Output
configuration the output
power will be reduced four times.
The OEM circuitry shall be designed to reduce the common mode noise typically
generated on the ground plane and to get the maximum power output from the
device (low resistance tracks).
(*) WARNING:
Using single ended configuration, the unused output line must be left open.
Not respecting this constraint, the output stage will be damaged.
“Ear_MT” Differential Line-out Drivers
Line coupling :
DC
Line type :
Differential
Output load resistance :
32
Ω
Signal bandwidth :
150 ~ 4000 Hz
@ -3 dB
Differential output voltage (MAX) :
734 mV
rms
Gain steps
7
Gain increment
3dB per step
“Ear_HF”
Fully Differential
Power Buffers
line coupling :
DC
line type :
Differential
output load resistance :
32
Ω
signal bandwidth :
150 ~ 4000 Hz
@ -3 dB
Differential output voltage (MAX) :
640 mV
rms
Gain steps
7
Gain increment
3dB per step
3.9.3.
General Design Rules
There are several possible configurations for the audio paths, but the two main types
are balanced and unbalanced microphone configurations.
The entire microphone path should be balanced even if this requires having two
wires connecting the microphone instead of the required one in the unbalanced case.