3.2 Schematics
C8
1200pf
J21
CON1
1
J22
CON1
1
SPK-
(PCM MODE CONTROL)
VCC
J23
CON4
1
2
3
4
C2
0.1uF
C1
0.1uF
SPK+
J19
CON1
1
C6
R12
2K
MIC-
J11
CON1
1
R7 20K
VCC
J15
CON1
1
C6
0.1uF
(PCM INPUT)
R6
27K
R9
27K
C5
0.1uF
J7
CON1
1
J8
CON1
1
Device Number
J5
CON1
1
(2.048 MHz MASTER CLOCK IN)
R10
1K
R1
1.5K
+
C4
4.7uF @10v
(PCM OUTPUT)
U1
W68XXXX
6
15
10
16
14
12
13
11
8
9
7
17
19
18
20
2
3
4
VD
D
VSS
PUI
u/A
FST
BCLKT
PCMT
MCLK
PCMR
BCLKR
FSR
AO
AI+
AI-
VAG
VREF
RO-
PAO+
PAI
PAO-
R11
0 Ohm
J2
CON1
1
Not Populated
R5 27K
VCC
J16
CON1
1
Not Populated
(FRAME SYNC RECEIVE)
Populated
J17
CON1
1
R2
1.5K
Not Populated
J12
CON1
1
J13
CON1
1
C7 1200pf
W6810
(BIT CLOCK TRANSMIT)
J9
CON1
1
W6810, W681512 or W681310
are Populated with C6 and R11 as shown
below.
R3 1K
R4 1K
W681310
(BIT CLOCK RECEIVE)
(POWER CONTROL)
Not Populated
J1
CON1
1
R11
J20
CON1
1
J3
CON1
1
(FRAME SYNC TRANSMIT)
J10
CON1
1
J18
CON1
1
J6
CON1
1
J4
CON1
1
VCC
MIC+
J14
CON1
1
C3
0.1uF
W681512
Populated
R8
3K
AO
FST
PAO+
BCLKT
FSR
VREF
U/A
MCLK
PCMR
PCMR
PAI
FST
AO
BCLKR
1
5
RO-
BCLKR
AI+
PUI
FSR
VAG
PAI
PUI
BCLKT
PCMT
VAG
VREF
U/A
RO-
PAO-
PCMT
MCLK
PAO-
PAO+
AI-
Pin1 Pin2
Pin3
Pin4
Mic+ Speaker- Mic -
Figure 1
:
EW681xxxES Board Schematics Telephone Handset Default Diagram
4 Connecting Microphone and Speaker to the W681xxxES
J23 can be used to connect an RJ9 plug from a “standard” telephone handset or headset to the
appropriate pins on the board (Table 4.0). The default resistor and capacitor values on the board are used
for the maximum amplification with no saturation of a 32ohm speaker using a standard microphone.
Unfortunately the only thing “standard” about the RJ9 handset jack is that the microphone and speaker are
always on the same pins. BUT, the microphone polarity can be positive, or negative, depending upon how
the manufacturer designed their telephone set. This means that one has about a 50% chance of wiring it
up wrong the first time UNLESS you know ahead of time which polarity handset you have. Many years
ago, with carbon microphones acting as variable resistors this was not an issue. But with today’s modern
handsets using polarized electret microphones polarity is very important. The circuit in Figure 1 assumes
that the positive side of the microphone is connected to pin 1 of the RJ9 plug and the negative side to pin 4.
Reversing the wires from the RJ9 to the holes in J23 will solve the polarity problem if there is no audio.
Table 4.0 : J23 Pin assignments
3
