Tektronix ECO8000 Series Service Manual

Theory of operation
Channel modul
es
The Channel modules contain the relays and electronic switches, which connect
either the primary or backup sync source to the output. There are two types of
Channel modu
les: REF/ELSW (ELectronic SWitch) and HREF/Relay.
REF / ELSW modules
The R EF/ELSW modules have a bandwidth of 50 MHz and normally use buffer
amplifiers to isolate and s witch the syncs. Since the switch is electronic, it creates
very littl
e disturbance to the sync signal. When power is lost, the REF/ELSW
module reverts to a latching relay connection to maintain the last selected signal
path.
HREF / Relay modules
The HREF
/Relay module uses wide-band relays to provide a switch path with a
bandwidth of 3 GHz. These relays are also latching so they retain state if the
ECO loses power.
PLD
Both ty
pes of Channel modules have a PLD to house local logic and to restore
state from a local EEPROM on power up. This restore is for the settings for
each channel, such as the threshold.
Peak detectors
Both
types of Channel modules have peak detectors that measure the
low-frequency energy of the primary and b ackup inputs to monitor the signal
level. This peak detector output is compared to a user-defined threshold to
determine if the signal is present. The signal presence lines go back to the Main
board PLD in order to drive the front-panel LEDs and to drive the logic that
makes the AUTO mode source-switch decision.
The output of each peak detector also goes into the voltage monitoring system.
This allows the diagnostic readout to provide level information on the input signal
a
nd to test the operation of the peak detector.
Interconnections
The interconnections to the Channel module are the inputs of power supplies,
clocks, SPI, JTAG, reset and t he source select. Outputs are the per-channel
fault signals for both the primary and backup inputs. Additionally, there is a
module-present line which gets grounded when a module is installed; the Main
board uses this to detect that a module is present. Finally there are four module
ID bits which have resistors to pull up or down to indicate the type of module
(REF/ELSW or HREF/Relay) and the number of channels (three or fi ve).
2–6 ECO8000 Series Service Manual

Tektronix ECO8000 Series Specifications

General

Brand	Tektronix
Model	ECO8000 Series
Category	Control Unit
Language	English