Tektronix LTA7P Series, Service Manual

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Theory of Operation
3- 2
TLA7Nx, TLA7Px, & TLA7Qx Logic Analyzer Module Service Manual
Power Supplies.
The Power Supplies r5 V, --5.2 V, +12 V, and +24 V
from the mainframe through the rear connectors to power the logic analyzer
module. Fuses protect the mainframe from over-current conditions. Voltage
converters produce addi5 V and +3.5 V supplies for use on the Acquisi-
tion board. The power connections to the Acquisition board are made through
one of the 100-pin ribbon cables and from the backplane.
Local Processor Unit Board Fuses.
Table 3--1 lists the fuses on the Local
Processor Unit board and briefly describes their function.
Table 3- 1: Local Processor Unit board fuses
Fuse Voltage Purpose
F1780 +5 V Supplies the 5 V-to-3.5 V DC converter. The converter powers
the 3 V PALS and the 3 V ASICs on the Acquisition board. The
converter also enables the +24 V-to-5 V DC to DC converter.
F1881 +5 V Supplies the microprocessor and the supporting circuitry.
F1681 +12 V Supplies the Control IC and MOSFET drivers for the 5 V-to-3.5
V DC to DC converter.
F1983 --24 V Supplies the +24 V-to-5 V DC to DC converter. This +5 V output
powers the acquisition RAM on the Acquisition board.
F1981 +24 V Supplies the +24 V-to-5 V DC to DC converter. This +5 V output
powers the acquisition RAM on the Acquisition board.
The acquisition board accepts input signals from the probes and converts them to
digital information. Two 100-pin ribbon cables provide interconnections with the
LPU board.
Clock Circuitry. The system clock is derived from the 10 MHz clock (from the
backplane) through a phase-locked loop. The acquisition run circuitry is
integrated with the clock circuitry to support time correlation.
Probe Interface.
Acquisition data passes from the probe input circuitry to the
probe receivers. Each probe receiver receives 16 data signals and one clock/qual-
ifier signal.
Two threshold voltages are generated for each probe input circuit (one for the
clock/qualifier signal and one for the 16 data signals). The threshold output
voltages are sent to the probe receiver. The threshold adjustment procedure,
performed by software, guarantees the accuracy of the reference voltages
provided to the probe receivers to achieve the desired low/high logic level
detection.
Acquisition Board