AD4693 datasheet(39/77 Pages) AD

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Data Sheet

AD4693/AD4694

MODES OF OPERATION

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Rev. 0 | 39 of 77

AUTONOMOUS MODE

In autonomous mode, SPI commands are used to start and stop

autonomous ADC sampling. The internal oscillator functions as the

ADC sampling clock, and is enabled and disabled by writing to

the OSC_EN bit in the OSC_EN_REG register. Setting OSC_EN

to 1 enables the internal oscillator to run and trigger conversions

until OSC_EN is set back to 0. After each conversion, ADC results

are pushed to the averaging filter of the corresponding channel,

and the channel sequencer updates the multiplexer to the next

channel in the sequence. After disabling the internal oscillator, the

ADC results are read back via the averaging filter or accumulator

output registers as described in the Averaging Filter Readback

section. Table 20 shows the configuration bit settings for selecting

autonomous mode and the desired stop state source.

Figure 68 shows a typical connection diagram for the digital host

and AD4693/AD4694 digital interface in autonomous mode. The

CNV input state is don't care in autonomous mode. Figure 69

shows a timing diagram of the OSC_EN SPI writes, the internal

oscillator, and SPI readback timing in autonomous mode.

Prior to performing conversions in autonomous mode, the internal

oscillator frequency, channel sequencer, and averaging filter set-

tings must be configured as described in the Theory of Operation

section, followed by a state reset.

Figure 96 illustrates the step-by-step configuration flow for AD4693/

AD4694 in autonomous mode.

Figure 68. Autonomous Mode Example Connection Diagram

Figure 69. Autonomous Mode Timing Diagram

AD4693 Datasheet(PDF) 39 Page - Analog Devices