WM_PRJ_Q2400_PTS_005 -007
18th January 2006
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Recommended characteristics for the speaker:
•
Type: 10 mW, electro-magnetic.
•
Impedance: 32 to 150
Ω
.
•
Sensitivity: 110 dB SPL min. (0 dB = 20 µPa).
•
Frequency response compatible with the GSM specifications.
For possible references, see chapter § 9.4.
2.3.2.3 Buzzer
Output
The buzzer output (BUZ) is a digital one. A buzzer can be directly connected
between this output and VBATT. The maximum current is 80 mA (PEAK).
A diode against transient peak voltage must be connected as described below.
Typical implementation:
C1
D1
VBATT
BUZ
R1
Figure 18: Example of Buzzer implementation
R1 must be chosen in order to limit the current at I
PEAK
max (recommended
values 10
Ω
to 50
Ω
).
C1 = 0 to 100 nF (depending on the buzzer type).
Recommended characteristics for the buzzer:
•
Type: electro-magnetic.
•
Impedance: 7 to 30
Ω
.
•
Sensitivity: 90 dB SPL min @ 10 cm.
2.3.2.4 Routing
constraints
To get better acoustic performances, basic recommendations are the following:
•
The SPKxx lines must be routed in parallel, without any wire in between.
•
The MICxx lines must be routed in parallel, without any wire in between.
•
All the filtering components (RLC) must be placed as close as possible to
the associated MICxx and SPKxx pins.
