Evaluation Kit for CMX612
EV6120
1.6
Detailed Description
1.6.1
Hardware Description - Evaluation Board
1.6.1.1 Line Interfacing.
The EV6120 is designed to work with a range of CLI simulators whilst connected to a PC and other
laboratory equipment. This has led to an opto-isolated line interface more akin to a modem than
commercial feature phones which are not designed to work with other equipment and are generally
not fully isolated from the line.
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Line protection is provided by R1 (47Ω), R2 (47Ω), and D1 (Philips BR211 series 140V). These
components are not fitted, but suitable values for UK applications are suggested in brackets. Wire
links which bypass R1 and R2 will need to be removed if these resistors are fitted.
Ring and line reversal detection is provided by an opto-isolated circuit formed by components C9,
D6, D10, R13, R50 and U2. Timing components R33 and C15 ensure a constant detect output for
a ring burst. See CMX612 data sheet for further details.
The transformer and op-amp hybrid (formed by U1:B and CMX612:AOP2) is connected to the
phone line by an optoMOS relay, U3. When ‘off-hook’ an adjacent LED is illuminated.
Line impedance matching is required in order to place signals on the line (acknowledgement tone
of type 2 / cidcw sequences) and to be able to send and receive speech and other signals (feature
phone mode).
These are suggested component values for various reference impedances using the EV6120
circuitry. Note that R22 adjusts the level of tx rejection on the rx side of the hybrid.
ref Z
600Ω(default)
900Ω
C25
C21
22nF
1nF
R16
0Ω
0Ω
C11
R19
R22
15nF
4n7F
150nF
4µ7F
4µ7F
3µ3F
510Ω
750Ω
750Ω
270kΩ
330kΩ
390kΩ
CTR21(complex)
56nF
240Ω
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A gyrator circuit draws dc loop current in the off-hook state. The current drawn may be altered by
adjusting the value of R28. This is designed to function with a dc current limited line.
Off-hook loads, specified for type1 CLI, can be applied by fitting the TELCO specific components
not fitted by CML.
An ac or dc load is provided by R4 (827Ω), R6 (1386Ω) and C3 (139nF). These components are
not fitted, but suitable values for UK applications are suggested in brackets. This load is switched
in by U12 and TR9. An LED is illuminated when this occurs.
A wetting pulse is provided by R7, which is not fitted. For UK applications, a suitable value may be
in the region of 240Ω to 350Ω. The wetting pulse is switched in by U13 and TR8. An LED is
illuminated when this occurs.
Consumer Microcircuits Limited
12
2000
UM6120/1
CMLMICRO [ CML MICROCIRCUITS ]
