
2
DEM-PCM3500
FIGURE 1. Schematic.
CONNECTORS
CN1 is the power supply connector for the DEM-PCM3500.
The +V
CC
pin may be set between +2.7V and +3.6V. The
GND pin should be connected to the negative (–) or ground
terminal of the power supply or battery, and functions as the
analog ground connection.
CN2 is the host interface connector. It includes connections for
the serial interface and system clock input/output. The connec-
tor pins correspond directly to the pin names of the PCM3500.
Refer to the PCM3500 data sheet for more details regarding the
operation and requirements for these connections.
CN3 is the analog input connector. The V
IN
pin is connected
to the PCM3500 analog-to-digital converter input, while the
GND pin is connected to analog ground. The full-scale input
voltage for V
IN
is 0.6V
CC
(in Vp-p), or 1.8Vp-p for a +3V
power supply.
CN4 is the analog output connector. The V
OUT
pin is con-
nected to the PCM3500 digital-to-analog converter output,
while the GND pin is connected to analog ground. The full-
scale output voltage at V
OUT
is typically 0.6V
CC
(in Vp-p),
or 1.8Vp-p for a +3V power supply.
DIP SWITCH SETTINGS
Table I shows the function of each switch setting for SW1.
Each switch corresponds directly to a pin of the PCM3500.
Refer to the PCM3500 data sheet for more details regarding
the operation and requirements for these pin functions.
TABLE I. DIP Switch Settings.
SW1
DESCRIPTION
PWDN
H = Power Down Disabled (normal operation)
L = Power Down Enabled
LOOP
H = ADC-to-DAC Loop Back Enabled
L = ADC-to-DAC Loop Back Disabled
HPFD
H = ADC High Pass Filter Disabled
L = ADC High Pass Filter Enabled
T/S
H = Time Slot Mode Enabled
L = Time Slot Mode Disabled
M/S
H = Master Mode Enabled
L = Slave Mode Enabled
CRYSTAL OSCILLATOR OPERATION
The PCM3500 contains an internal crystal oscillator circuit.
The oscillator can be used to generate the 512f
S
system clock
(512 times the desired sample frequency). The crystal value
must be equal to 512f
S
. A fundamental mode, parallel
resonant crystal is recommended. The load capacitors, C
S
,
should be set in the range from 10pF – 33pF, with 22pF
being the typical value. When using the crystal oscillator,
BCK and FS should be derived from SCKIO when using
Slave mode. Alternatively, the PCM3500 may be set to
Master mode so that the BCK and FS are generated by the
CODEC itself.
V
COM
V
REF
1
V
REF
2
V
IN
AGND
M/S
TSC
BCK
FS
DIN
DOUT
FSO
V
CC
AGND
V
OUT
AGND
PDWN
LOOP
HPFD
XTI
XTO
SCKIO
DGND
V
DD
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
U1
PCM3500
PWDN
P
L
H
T
M
SW1
DSS105
LOOP
HPFD
DOUT
FSO
FS
DIN
BCK
SCKO
GND
XTI
CN2
VH8
V
OUT
GND
CN4
VH2
C
1
1
μ
F
C
2
2.2
μ
F
+
C
3
4.7
μ
F
+
C
4
4.7
μ
F
+
+
SCKIO
XTI
C
6
0.1
μ
F
C
7
4.7
μ
F
+
C
11
1
μ
F
+
V
IN
GND
CN3
VH2
GND
V
CC
CN1
VH2
PDWN
LOOP
HPFD
SCKIO
+
C
8
4.7
μ
F
C
5
0.1
μ
F
+
C
10
0.1
μ
F
C
9
100
μ
F
C
S
C
S
XTAL
OPTIONAL
XTI