User`s guide

Chapter 4 Theory of Operation

D-to-A Converter

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.