AD4697 datasheet(52/107 Pages) AD

52 / 107 page

Data Sheet

AD4697/AD4698

DIGITAL INTERFACE

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Rev. 0 | 52 of 107

CONVERSION MODE

When the AD4697/AD4698 are in conversion mode, CNV rising

edges initiate conversions on the selected channel, and the chan-

nel sequencing logic updates the multiplexer to the next channel

(see the Converter Operation and Channel Sequencing Modes sec-

tions). The device enters conversion mode when the SPI_MODE bit

in the setup register is set to 1.

In conversion mode, the SPI is used to read the ADC results

and write the 5-bit SDI commands shown in Table 18. Figure 94

to Figure 101 show timing diagrams for SPI frames relative to

performing conversions. The CNV signal and the CS pin can be

tied together to enable interfacing with a single 4-wire SPI port (see

Figure 101). Each ADC result is available until the next CNV rising

edge occurs.

An optional set of five status bits can be appended to the ADC

data. The status bits include channel information, the overvoltage

clamp flag, and a threshold detection alert indicator. See the Status

Bits section for a description of the status bits and how they are

enabled.

In conversion mode, the general-purpose pins can be assigned

as an additional serial data output to reduce the SCK frequency

required to shift out the ADC result plus optional status bits before

the next conversion occurs. See the Serial Data Output Modes

section for a description of the options available on both package

options of the AD4697/AD4698 and how to enable these modes.

The general-purpose pins can also be assigned as either the busy

indicator or the threshold detection alert indicator. Figure 94 to

Figure 101 show the relative timing of the CNV signal and the busy

and alert indicators when they are assigned to the general-purpose

pins. The General-Purpose Pins section describes how to set the

general-purpose pins to the desired function.

When autocycle mode is enabled, the AD4697/AD4698 generate

their own internal convert start signal to autonomously perform

conversions without a CNV signal from the digital host (see the

Autocycle Mode section).

Status Bits

A set of five status bits can be appended to the end of each

conversion result. The status bits allow the digital host to monitor

the status of the analog inputs without interrupting analog-to-digital

conversions. Table 17 shows the names and descriptions of the

status bits.

By default, the OV_ALT status bit indicates the status of the over-

voltage clamp flags (the bitwise logical OR of the CLAMP_FLAG

bit and COM_CLAMP_FLAG bit in the status register). When the

OV_ALT_MODE bit in the GP_MODE register is set to 1, the

OV_ALT status bit is the logical OR of the CLAMP_FLAG bit and

the threshold detection alert indicator (TD_ALERT bit in the status

detect and respond to out of range events.

The INX bits indicate which of the eight analog inputs the conver-

sion result corresponds to. The values for the INX bits range from

0 to 7 (0x0 to 0x7) and correspond to IN0 to IN7, respectively. An

INX value of 15 corresponds to the temperature sensor. The INX

bits can be used by the digital host to align the ADC data with the

sequence of analog input channels.

Set the STATUS_EN bit in the setup register to 1 to enable the

status bits. The status bits are disabled by default. When the status

bits are enabled, the serial data output word extends to 24 bits,

where Bit 20 to Bit 24 contain the status bits (see Table 21,

Table 22 and Table 23).

Table 17. Status Bits Names and Descriptions

Status Word Index

Bit

Name

Description

Bit 4

OV_ALT Active high. Indicates the status of the overvoltage protection clamp flag and (if enabled) the status of the threshold detection alert

indicator.

Bits[3:0]

INX

Indicates what analog input channel the ADC data corresponds to (IN0 to IN7).

Table 18. Conversion Mode Commands

Channel Sequencing Mode

5-Bit SDI Command (CMD)

Description

Two-Cycle Command Mode and Single-Cycle Command Mode

0x00 to 0x09, 0x0B to 0x0E

NOOP

0x0A

0x0F

Temperature sensor channel selection

0x10 to 0x17 and 0x18 to 0x1F

IN0 to IN7 channel selection

Standard Sequencer and Advanced Sequencer

0x00 to 0x09, 0x0B to 0x1F

NOOP

0x0A

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