Chapter 4 Theory of Operation
D-to-A Converter
90
D-to-A Converter
Referring to the schematic shown on page 13 1, all re ference 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 m sec to maintain its output setting. Changes to track/hold amplifier
outputs are accomplished by dwelling on that position for an extended pe riod.
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