AD7294 datasheet(23/45 Pages) AD

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Preliminary Technical Data

AD7294

Rev. PrB | Page 23 of 45

The AD7294 contains 43 internal registers (see Figure 27) that

are used to store conversion results, high and low conversion

limits, and information to configure and control the device.

There are 42 data registers and one address pointer register.

ADDRESS

POINTER

COMMAND REGISTER

RESULT REGISTER

TSENSE RESULT

REGISTERS

x 3

ALERT REGISTERS

CHANNEL SEQUENCE

CONFIGURATION

POWER DOWN

DATAHIGH /DATALOW

REGISTERS

x 18

HYSTERESIS REGISTER

TSENSE OFFSET

REGISTERS

x 2

FUSE BLOCK

REGISTERS

x 2

SERIAL BUS INTERFACE

SDA

SCL

Figure 27. AD7294 Register Structure

Each data register has an address to which the address pointer

write-only registers; the rest are read/write registers.

ADDRESS POINT REGISTER

The address pointer register does not have and does not require

an address, because it is the register to which the first data byte

of every write operation is written automatically. The address

pointer register is an 8-bit register, in which the 6 LSBs are used

as pointer bits to store an address that points to one of the

AD7294’s data registers, see Table 11. The first byte following

each write address is the address of one of the data registers,

which is stored in the address pointer register and selects the

data register to which subsequent data bytes are written. On

power-up, the address pointer register contains all 0s, pointing

to the command register.

ADC CHANNEL ALLOCATION

These nine channel address bits select which analog input

channel is to convert using the multiplexer, see Table 7.

Choosing Channels 1 to 4 selects the standard analog voltage

inputs. Channels 5 and 6 represent the analog-input sense

amplifiers for current monitoring. Channel 7 and 8 designate

the use of the external temperature-sensing diodes, whereas

Channel 9 represents the internal temperature sensor.

Table 7. ADC Channel Allocation

Channel

Function

Channel ID

CH1

VIN0 or (VIN0 − VIN1)

000

CH2

VIN1 or (VIN1 − VIN0)

001

CH3

VIN2 or (VIN2 − VIN3)

010

CH4

VIN3 or (VIN3 − VIN2)

011

CH5

ISENSE1

100

CH6

ISENSE2

101

CH7

TSENSE1

110

CH8

TSENSE2

111

CH9

TSENSEINT

–

There are two modes of operation with respect to the ADC. In

command mode, a sequence is written to the ADC, and on

subsequent reads, the next channel in the sequence is converted

as the current sequence is read out. In autocycle mode, a

sequence is programmed, and then the ADC automatically

cycles through the selected channels, outputting an alert if one

of the channels goes outside its preset range.

AD7294 Datasheet(PDF) 23 Page - Analog Devices

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