MLX32001 View Datasheet(PDF) - Melexis Microelectronic Systems
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MLX32001 Datasheet PDF : 11 Pages
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MLX32001
Universal PSTN Line Interface
where MLX32001 is powered and accordingly adapt
optimally to that telephone network. This means that
MLX32001 is capable of measuring all relevant DC
and transient phenomena on a telephone line that
characterise this line. Consequently settings can be
optimised for (extremely) long line operation, low
current operation, parallel operation with 1 or more
telephones in parallel, line monitoring (detect line
transients, line parallel pickup and replace and total
line disconnect).
In a PC controlled environment, parameters and drivers are
residing in the PC’s memory, while the front end (USB)
controller such as the USB Cypress C7Y67001 is performing
bitwise control and is handling the UART.
MLX32001 is not only a fully line powered device, it also
generates power supply for local hosting microcontrollers. It
has 2 different sources of power supply generation: AUX5,
AUX10 delivering 5 and 10mA nominally if sufficient line
current is available. The AUX5 supply can be programmed in
steps of 20µA. This allows the designer to modify the
HOST's supply current while exactly regulating the supply
voltage with just an internal A/D convertor input on the
HOST.
supply from the HOST to the PSTN side, giving possible
problems for lightning safety, radio interference at higher
frequencies and frame ground sensitive coupling problems.
The AC-handler part of the design has not been integrated
into MLX32001 for 2 major reasons:
1) In designs that include a galvanic separation, the DC-
handler is on the line powered side, while the AC-
handler resides on the HOST powered side. Since
MLX32001 supports each possible line transformer,
the DC-handler section is identical for all designs,
while the AC-handler part depends very much on line
transformer selection.
2) For galvanically coupled designs the STMR filters
used require capacitor values up to 2.2µF. Integrating
such high values into silicon will either be expensive
or (with some impedance conversion tricks) will result
in a Total Harmonic Distortion of the transmitting
stage that is higher than the 72dB required by V.90
modems. To allow any design to work with
MLX32001 it was decided to build up any appropriate
AC-handler by conventional components, thus
reaching the best possible THD levels as well as the
most cost effective total design setup.
With those features it is possible to built standalone (modem)
applications with hosting controllers like NEC
UPD78F9177G, Texas Instruments MSP430-series and
Hitachi H8-36XX series. These controllers are then fully line
powered but still perform powerful functions like full V.22
modem implementation, S0 contact scanning for utility
meters, E-data transfer interface for POS and E-cash modules
etc.
Any line interface requiring galvanic separation has a line
powered PSTN-side and a HOST controller side where
primary controlling power is available. With the MLX32001
there is a consistent and dominant separation between AC
and DC handling:
§ All non-AC handling is regarded as DC handling and is
performed by MLX32001 at the PSTN-powered side,
including (im)pulse dialing, overshoot control, polarity
detection, hookswitch control, ring detection and line
event monitoring. For universal line interface designs,
the DC handling part is always identical
§ All pure AC-handling is performed at the HOST side, as
it differs from application to application and depends on
AC line transformer choice, the number of reference
termination sections and the number of SMTR feedback
filter elements.
For worldwide coverage of Balanced Return Loss 2
impedances are needed. If the design specification is limited
to 600E terminating countries only 1 is required. The
excellent THD and Noise characteristics are the result of the
fully line powered operation. Other DAA's transfer power
Interworking reliability is the most important aspect of any
global line interface. MLX32001 design setup has been done
together with a traditional AC-type line transformer for
galvanic barrier implementation. This has the following
advantages:
1) The setup is totally safe for common mode lightning:
there are no high voltage capacitors required between
the PSTN powered side and the HOST powered side.
Since the coupling is inductive, the higher the
frequency, the higher the impedance and the lower the
coupling currents.
2) Proven and reliable electromagnetic coupling
technology
3) 4kV of separation can be reached supporting global
access with 1 transformer
4) 2 standard PC-817 opto-couplers are sufficient to pass
all MLX32001 digital control signals
Finally, MLX32001 supports full line event monitoring. This
means that any line event occurring in online or offline mode
will generate an event within MLX32001 where the host
decides what to do with it. For modems, this means that other
telephones picked up and replaced in parallel can be properly
handled without closing down the connection or terminating
the download procedures. Also MLX32001 can be linked
'virtually' online. In this mode, MLX32001 based designs
never answer incoming calls and never originate calls during
line busy states. Also the actual line use versus daytime
period is 'monitored' and it is consequently decided what is
the best period to make service calls or autodownload
configuration data.
Page 3 of 11
MLX32001 Universal PSTN Line Interface / Rev1.2
17 May 2000
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