73M2901CL
V.22bis Single Chip Modem
MODEM PERFORMANCE
CHARACTERISTICS
The curves presented in this data sheet define
modem IC performance under a variety of line
conditions typical of those encountered over Public
Switched Telephone Network.
BER VS. SNR
This test represents the ability of the modem to
operate over noisy lines with a minimum amount of
data transfer errors. Since some noise is generated
in the best dial up lines, the modem must operate
with the lowest signal to noise ratio (SNR) possible.
Better modem performance is indicated by test
curves that are closest to the BER axis. A narrow
spread between curves representing the four line
parameters indicates minimal variation in
performance while operating over a range of typical
operating conditions. A DPSK modem will exhibit
better BER performance test curves receiving in the
low band (answer mode) than in the high band
(originate mode).
BER VS. RECEIVE LEVEL
This test measures the dynamic range of the
modem. Because signal levels vary widely over dial
up lines, the widest possible dynamic range is
desirable. The SNR is held constant at the indicated
values as the Receive level is lowered from a very
high to a very low signal level. The width of the bowl
of these curves, taken at the BER break points is the
measure of the dynamic range.
RECOMMENDED SCHEMATIC ARRANGEMENT
VCC3_3D
11.0592 MHz
+
C1
10uF
RST
R1
10K
TXDB
VCC3_3D
C11
0.1uF
+
C12
10uF
TXDB
OSCIN
OSCOUT
C13
+
10uF
0.1uF
R15
5.1K
C20
RXA
0.1uF
16
15
RXA
14
VBG
13
VREF
12
TXAP
11
10
9
RST
C7
2901CL_TQFP32
1
2
3
4
5
6
7
8
0.1uF
C8
0.1uF
R23
NC
R13
21K
TXAN
VCC3_3A
+
C9
22uF
C10
0.1uF
R2
2K
TXAN
U2
R28
120K
6
5
4
2
LDA110*
VCC3_3D
1
RINGB/PPUB/LIUB/LREVB
DCDB
DSRB
CTSB
RTSB
DCDB
DSRB
CTSB
RTSB
4
U3
TLP627
R18
100
2
3
4
U4
TLP627
R16
100
HOOKB
U11P2
2
3
LIUCHECKB
U10P2
1
RXA_TAP
C4
.082UF
C20R29
4
1
671-8005
C14
TXAP
C2
Y1
27pF
OSCOUT
C3
33pF
ISOLATION BARRIER
R17
475
T1P3
T1
3
2
VCC3_3D
U1
J1
CON10
10
9
8
7
6
5
4
3
2
1
RXDB
DTRB
TXDB
RIB
DCDB
DSRB
CTSB
RTSB
VCC3_3
25
RXDB
26
27
DTRB
28
29
30
HOOKB
31
RIB
32
VCC3_3A
R20
22K
VND
VPD
DCD
DSR
CTS
RTS
USR11
USR10
C5
10uF
VPD
RXD
RXCLK
DTR
USR20
RING
RELAY
RI
TXCLK
TXD
VND
N/C
VPD
OSCIN
OSCOUT
VND
24
23
22
21
20
19
18
17
VNA
RXA
VBG
VREF
TXAP
TXAN
VPA
RESET
+
C6
1
0.1uF
VCC3_3D
VCC3_3
VCC3_3D
[js1]
11
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