SX1441EVK Semtech, SX1441EVK Datasheet - Page 68

• Manufacturer Part Number: SX1441EVK
• Description: KIT DEV FOR SX1441
• Manufacturer: Semtech
• Series: EasyBlue™r
• Type: Bluetoothr

Specifications of SX1441EVK

• For Use With/related Products: SX1441
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Contents: -
• Other names: SX1441DVK; SX1441DVK

Personal Area Network
3.14.6 Microphone Input
The Figure 31 shows how to connect the microphone. The microphone is powered by the pin VREGA, or any clean
constant voltage through the resistor R
The Figure 30 shows the equivalent schematic for gain and dynamic range calculation. The input impedance of the
preamplifier, the polarization resistor, and the internal resistor of the microphone are to be considered in parallel.
The input impedance of the preamplifier varies with the preamplifier gain.
Figure 32 is the equivalent schematic for the C
the relation:
Z
is usually about a few kΩ and depends on the microphone.
3.14.7 Speaker Output
The power amplifier operates in class D. The pins PA_OUTP and PA_OUTN output two complementary digital
signals (see Figure 33) at high frequency and whose cyclic ratio is proportional to the amplitude of the audio signal.
The PWM switching frequency has to be filtered to limit power consumption and risk of degradation of the speaker.
© Semtech 2006
in
varies from 5 kΩ to 20 kΩ, depending on the gain of the preamplifier. CMIC is typically about 470 nF. R
Figure 31 - typical microphone configuration
Q1
R
em
C
C
MIC
MIC
R
pol
VMIC_P
VMIC_N
VREGA
SX1441
pol
. The two capacitors C
f
MIC
L
=
and low frequency roll-off calculations. The frequency is given by
2
π
⋅
Z
68
in
1
⋅
C
Figure 30 - Equivalent schematic for gain calculation
Figure 32 - Equivalent schematic for C
The
MIC
MIC
remove the DC voltage level.
×
2
C
MIC
SX1441 – Bluetooth® 1.2 SoC
preamplifier
preamplifier
MIC
www.semtech.com
calculation
Data Sheet
pol
value