TLE2301 Datasheet, PDF (14/22 Pages) Texas Instruments – EXCALIBUR 3-STATE-OUTPUT WIDE-BANDWIDTH POWER OPERATIONAL AMPLIFIER

TLE2301
EXCALIBUR 3-STATE-OUTPUT WIDE-BANDWIDTH
POWER OPERATIONAL AMPLIFIER
SLOS131 – DECEMBER 1993
APPLICATION INFORMATION
circuit for mains-line driver over 40-kHz-to-90-kHz utility band
The following application is a circuit for a mains-line driver over 40-kHz-to-90-kHz utility band and is based
around the European standard (EN56065 –1) describing utility and consumer applications. This example shows
a possible implementation for differential transmission on the mains line. This applications circuit is designed
around the requirements of a domestic electricity meter operating over a utility band of 40 kHz to 90 kHz. A
dual-rail power supply of ± 5 V is used for this design example to limit device power dissipation. The same design
principles, however, can be applied to other applications.
frequency band
The frequency band for utility applications extends over an enormous range from 3 kHz to 95 kHz. In order to
have a coupling network that is economical and implemented with readily available components, this circuit is
designed for a subband from 40 kHz to 90 kHz.
This subband is sufficiently wide to support multichannel operation; i.e., 10 channels of 5 kHz width or more if
the channel widths are smaller. To avoid transmission spillover into the next band, a guard band of 5 kHz is
allowed. The upper frequency of this circuit is set to 90 kHz, and the lower frequency is chosen for an economical
coupling network and still has sufficient bandwidth to support multichannel operation.
output drive
The impedance of the mains network at these signalling frequencies is relatively low (<1 Ω to 30 Ω). This circuit
has been designed to drive a 4-Ω mains line over the 40-kHz-to-90-kHz bandwidth.
The signalling impedance of the mains network fluctuates as different loads are switched on during the day or
over a season, and it is influenced by many factors such as:
D Localized loading from appliances connected to the mains supply near to the connection of the
communication equipment; e.g., heavy loads such as cookers and immersion heaters and reactive loads
such as EMC filters and power factor correctors
D Distributed loading from consumers connected to the same mains cable, where their collective loading
reduces the mains signalling impedance during times of peak electricity consumption; e.g., meal times
D Network parameters; e.g., transmission properties of cables and the impedance characteristics of
distribution transformers and other system elements
With such a diversity of factors, the signalling environment fluctuates enormously, irregularly, and can differ
greatly from one installation to another. The signalling system should be designed for reliable communications
over a wide range of mains impedances and signalling conditions. Consequently, the transmitter must be able
to drive sufficient signal into the mains network under these loading conditions.
The TLE2301 amplifier has 1-A output drive capability with short-circuit protection; hence, it adequately copes
with the high current demands required for implementing mains signalling systems.
3-state facility
When transmitting, the transmitter appears as a low-impedance signal source on the mains network. If
transmitters are left in the active mode whether transmitting or not and a large number of transmitters are
installed in close proximity, their combined loading would reduce the mains impedance to unacceptable levels.
Not only would each transmitter need to drive into an extremely low mains impedance, but signals arriving from
distant transmitters would be severely attenuated.
To overcome this problem, the transmitters need to present a high impedance to the mains network when they
are not transmitting. The mains network is then only loaded by a few transmitters at any one time, and the mains
signalling impedance is not adversely affected.
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