+5V Multiprotocol, Software-Selectable
Cable Terminator
A
A
I
AMMETER
VDM = ±2V
R1 = 52Ω
S1 ON
R3 = 127Ω
S2 OFF
R2 = 52Ω
B
VCM = ±7V OR ±2V
RDM
=
VDM
I
Figure 1. V.11 or V.35 Differential Impedance Measurement
R1 = 52Ω
AMMETER
I
VCM = ±2V
RCM
=
VCM
I
S1 ON
R3 = 127Ω
S2 ON
R2 = 52Ω
B
Figure 2. V.35 Common-Mode Impedance Measurement
1 M0
24 M1
MXL1344A
23 M2
22 DCE/DTE
21 LATCH
VCC VEE
14 2
3 8 11 12 13
12 34 5 6
5 4 6 7 9 10 16 15 18 17 19 20
Figure 3. Block Diagram
chipset must be used without substituting other manu-
facturer's parts on a chip-by-chip basis.
Termination Modes
The termination networks in the MXL1344A can be set
to one of three modes, V.11, V.35, or high impedance
(high-Z). As shown in Figure 4, in V.11 mode, switch S1
is closed and switch S2 is open, presenting 104Ω
across terminals A and B. In V.35 mode, switches S1
and S2 are both closed, presenting a T-network with
104Ω differential impedance and 153Ω common-mode
impedance. In high-Z mode, switches S1 and S2 are
both open, presenting a high impedance across termi-
nals A and B suitable for V.28 and V.10 modes.
_______________________________________________________________________________________ 5