Technical data

Analog Integrated Circuit Device Data
34 Freescale Semiconductor
34825
TYPICAL APPLICATIONS
TYPICAL APPLICATIONS
DECOUPLING CAPACITOR
Decoupling capacitors are required at all power supply
input and output pins. For the VDD pin, a X5R capacitor of
1.0
F is recommended. For VBUS pin, because it also acts
as the microphone input, the decoupling capacitance at
VBUS pin must be carefully considered. Assuming the voice
band is 3.4
kHz and the pull-up resistance for the microphone
is 2.0 k, the decoupling capacitance at the VBUS pin should
be less than 22 nF. A 4.7 nF X5R capacitor is recommended
for the typical application. The OUT pin requires a 1.0
F
decoupling capacitor; a 0.01 F capacitance is enough for
the VDDIO pin.
TYPICAL APPLICATIONS
INTERFACE CIRCUIT IN A CELL PHONE
When the 34825 is used in a cell phone. The typical circuit
is shown in the Figure 27. The I
2
C bus need two pull-up
resistors. Typically they are 4.7 kWhen the audio outputs
of the cell phone baseband or application processor are
direct drive signals, the audio signals can be connected to the
corresponding pins of 34825 directly. Otherwise these
signals need DC-blocking capacitors to remove the DC level.
Figure 27. Interface Circuit in a Cell Phone System
V
DDIO
I
2
C_SDA
I
2
C_SCL
INT
VDDIO
RxD
TxD
D+
D-
VDD
ID
DP
DM
GND
VBUS
ID
D+
D-
GND
I
2
C
UART
USB Xcvr
GPIO
Baseband
SHLD
OUT
VBUS
MC34673
ISET
Audio
4.7 nF
1.0 µF
Li+
1.0 µF
9.1 k12 k
2x4.7 k
MIC
SPK_L
SPK_R
2 k
V
AIO
*
*
For direct-drive audio output, these DC
blocking capacitors are not needed
* :
0.1 µF