Block Diagram 5
Keysight 33210A Service Guide 107
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 page 110.
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.
The 14–bit waveform DAC is loaded with data from the Synthesis IC. The output is
then fed through one of two filters before being buffered and sent to the Main
Output Circuitry. The two filters are:
–A 9
th
order elliptical filter with a cutoff frequency of 23.5 MHz. This filter
includes sin (x)/x correction. This filter is used for continuous sine and
squarewaves.
–A 7
th
order linear phase filter with a cutoff frequency of 12.5 MHz. This filter is
used for ramp, noise, and arbitrary waveforms.
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