TDS 200 Series Digital Oscilloscope Service Manual
3–1
Theory of Operation
This chapter describes the electrical operation of the TDS 200-Series Digital
Real-Time Oscilloscope to the module level. It describes the basic operation of
each functional circuit block shown in figures 3–1 and 3–2.
Main Board
The Main board contains a two or four channel acquisition system, trigger
system, acquisition/display controller, and system processor. Interfaces are
provided for two signal inputs, external trigger input, probe compensation, front
panel, LCD display, extension module, and power supply. Acquisition and
display functions are implemented in two application specific integrated circuits
(ASICs).
Signals from the CH 1, CH 2, and EXT TRIG, or CH 1, CH 2, CH 3, and CH 4
input connectors pass through attenuators to the acquisition ASIC. The acquisi-
tion ASIC contains amplifiers and samplers for each input channel, A/D
converter, and trigger logic. The digitized waveform samples are transferred to
the display ASIC. Low voltage regulators supply isolated power to the acquisi-
tion ASIC.
The display system consists of the display ASIC, DRAM memory, and system
oscillator. Digitized acquisition samples are processed by the display ASIC and
stored into DRAM. The Display ASIC formats the waveform data and generates
drive signals for the LCD display. Front panel scanning is also performed by the
display ASIC.
The processor system consists of the microprocessor and memory. The processor
system interprets the front panel controls, programs acquisition and display
parameters, computes waveform measurements, and manages the extension
module interface. Saved setups, waveforms, and calibration constants are stored
in nonvolatile memory. The processor system shares DRAM with the display
system.
BNC connectors are mounted on the main board for the CH 1, CH 2, and trigger
or CH 1, CH 2, CH 3, and CH 4 inputs. The signal inputs are compatible with the
P2100 probes supplied.
The PROBE COMP and ground terminals are provided for probe adjustment.
Acquisition System
Display System
Processor System
Input Signal Interface
Probe Compensation
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