Data Sheet

AD7699

Rev. F | Page 29 of 32

CHANNEL SEQUENCER

The AD7699 include a channel sequencer useful for scanning

channels in a repeated fashion. Channels are scanned as singles

or pairs, with or without the temperature sensor, after the last

channel is sequenced.

The sequencer starts with IN0 and finishes with IN[7:0] set in

CFG[9:7]. For paired channels, the channels are paired depend-

ing on the last channel set in CFG[9:7]. Note that in sequencer

mode, the channels are always paired with the positive input on

the even channels (IN0, IN2, IN4, and IN6), and with the

negative input on the odd channels (IN1, IN3, IN5, and IN7).

For example, setting CFG[9:7] = 110 or 111 scans all pairs with

the positive inputs dedicated to IN0, IN2, IN4, and IN6.

CFG[2:1] are used to enable the sequencer. After the CFG

register is updated, DIN must be held low while reading data

out for Bit 13, or the CFG register begins updating again.

Note that while operating in a sequence, some bits of the CFG

register can be changed. However, if changing CFG[11] (paired

or single channel) or CFG[9:7] (last channel in sequence), the

sequence reinitializes and converts IN0 (or IN0/IN1 pairs) after

the CFG register is updated.

Figure 43 details the timing for all three modes without a busy

indicator. The sequencer can also be used with the busy

indicator and details for these timings can be found in the

General Timing With a Busy Indicator section and the

Read/Write Spanning Conversion with a Busy Indicator section.

For sequencer operation, the CFG register must be set during

the (n − 1) phase after power-up. On phase (n), the sequencer

setting takes place and acquires IN0. The first valid conversion

result is available at phase (n + 1). After the last channel set in

CFG[9:7] is converted, the internal temperature sensor data is

output (if enabled), followed by acquisition of IN0.

Examples

With all channels configured for unipolar mode to GND,

including the internal temperature sensor, the sequence scans in

the following order:

IN0, IN1, IN2, IN3, IN4, IN5, IN6, IN7, TEMP, IN0, IN1, IN2…

For paired channels with the internal temperature sensor

enabled, the sequencer scans in the following order:

IN0, IN2, IN4, IN6, TEMP, IN0…

Note that IN1, IN3, IN5, and IN7 are referenced to a GND

sense or VREF/2, as detailed in the Input Configurations section.

ACQUISITION

(n – 1) UNDEFINED

ACQUISITION

(n), IN0

ACQUISITION

(n + 1), IN1

ACQUISITION

(n + 2), IN2

PHASE

POWER

UP

EOC

EOC

SOC

EOC

EOC

CONVERSION

(n – 1) UNDEFINED

CONVERSION

(n), IN0

CONVERSION

(n + 1), IN1

CONVERSION

(n – 2) UNDEFINED

tCONV

tCYC

tDATA

CNV

CNV

CNV

DIN

SDO

XXX

MSB

XXX

MSB

XXX

NOTES

1. CNV MUST BE HIGH PRIOR TO THE END OF CONVERSION (EOC) TO AVOID THE BUSY INDICATOR.

2. A TOTAL OF 16 SCK FALLING EDGES ARE REQUIRED TO RETURN SDO TO HIGH-Z. IF CFG READBACK IS ENABLED,

A TOTAL OF 30 SCK FALLING EDGES IS REQUIRED TO RETURN SDO TO HIGH-Z.

DATA IN0

DATA (n – 1)

XXX

DATA (n – 1)

XXX

DATA (n – 1)

XXX

DATA (n – 1)

XXX

DATA (n – 2)

XXX

DATA (n – 2)

XXX

DATA (n – 2)

XXX

DATA (n – 2)

XXX

DATA (n – 3)

XXX

DIN

SDO

DATA IN1

DATA IN0

DATA IN0

DATA IN0

DATA IN1

DIN

CFG (n)

CFG (n)

SDO

SCK

1

NOTE 1

16

16

16

16

NOTE 2

NOTE 2

NOTE 2

2

1

1

1

SCK

1

16

16

16

n

n

n

n

n + 1

n + 1

n + 1

1

1

SCK

1

1

1

16

16

16

1

1

CFG (n)

RDC

RAC

RSC

CFG (n)

Figure 43. General Channel Sequencer Timing Without a Busy Indicator