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Chapter 4 Theory of Operation
D-to-A Converter
90
D-to-A Converter
Referring to the schematic shown on page 131, all reference voltages of power
circuits are derived from the internal voltage reference of system DAC U22.
The system DAC track/hold amplifier outputs are used to provide controllable
reference voltages to power circuits. The system DAC is programmed and
responds to the main controller via internal 3-wire serial data bus SERCLK,
SERRBK, and SERSTB. The system DAC is multiplexed to 6 track/hold
amplifiers through U26. Each track/hold amplifier is refreshed approximately
every 1 msec to maintain its output setting. Changes to track/hold amplifier
outputs are accomplished by dwelling on that position for an extended period.