Keysight 33210A, Service Manual

Page: 99 / 131

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Chapter 5 Block Diagram
Block Diagram
4
5
Block Diagram
The function generator’s circuits may be divided into three main
categories: power supplies, analog circuits, and digital circuits. The
instrument is further divided into floating and earth referenced
circuitry.
This discussion refers to the block diagram on page 100.
The Main Processor combines many instrument functions onto one
custom IC. It interfaces directly with the GPIB and LAN interfaces, and
through a controller chip with the USB interface. A 50 MHz crystal
oscillator provides the clock signal for U101 operations. A 24 MHz clock
is used for USB operations.
The Main Processor communicates with the Front Panel and performs
the keyboard scanning. Serial data is used to write to the display. The
cross-isolation communication with the Synthesis IC uses optically
isolated serial data links.
The Synthesis IC is a gate array and performs most of instrument
functions. This gate array has an on-board UART. A 50 MHz voltage-
controlled-oscillator provides the main clock for the Synthesis IC and the
Waveform DAC. The Synthesis IC implements clock generation, pulse
generation, DDS and modulation functions, and sets the output
waveform and function.
The system DAC outputs various control voltages that are multiplexed
into track and hold circuits. These output voltages are used to correct the
output waveform for various offsets, rise times, and calibration values. If
present, the optional external timebase circuitry provides an input and
output for an external time base. A Sync Out signal is available at the
front panel.
Some of the output voltages are read back to the Synthesis IC via the
System ADC. Here, voltages from various circuits in the instrument are
multiplexed with the Modulation IN signal and measured by the
Synthesis IC.