AD7933/AD7934

Preliminary Technical Data

CONTROL REGISTER

The control register on the AD7933/AD7934 is a 12-bit, write-only register. Data is written to this register using the CS and WR pins. The

control register is shown below and the functions of the bits are described in

. At power-up, the default bit settings in the control

register are all 0s.

Table 7

Table 7. Control Register Bit Function Description

Table 6. Control Register Bits

MSB

LSB

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

PM1

PM0

CODING

REF

ZERO

ADD1

ADD0

MODE1

MODE0

SEQ1

SEQ0

RANGE

Bit No.

Mnemonic

Description

11, 10

PM1, PM0

Power Management Bits. These two bits are used to select the power mode of operation. The user can choose

between either normal mode or various power-down modes of operation as shown in

.

9

CODING

This bit selects the output coding of the conversion result. If this bit is set to 0, the output coding is straight

(natural) binary. If this bit is set to 1, the output coding is twos complement.

8

REF

This bit selects whether the internal or an external reference is used to perform the conversion. If this bit is Logic 0,

the Reference Section).

7

ZERO

This bit is not used so it should always be set to Logic 0.

6, 5

ADD1,

ADD0

These two address bits are used to either select which analog input channel is to be converted in the next

conversion, if the sequencer is not being used, or to select the final channel in a consecutive sequence when the

sequencer is being used as described in

. The selected input channel is decoded as shown in

.

4, 3

MODE1,

MODE0

single-ended inputs, two fully differential inputs, or two pseudo-differential inputs (see

).

2

SEQ1

The SEQ1 bit in the control register is used in conjunction with the SEQ0 bit to control the sequencer function (see

).

1

SEQ0

The SEQ0 bit in the control register is used in conjunction with the SEQ1 bit to control the sequencer function (see

).

0

RANGE

This bit selects the analog input range of the AD7933/AD7934. If it is set to 0, the analog input range extends from

must be 4.75 V to 5.25 V.

Table 8

Table 8. Power Mode Selection using the Power Management Bits in the Control Register

Table 10

Table 10

Table 10

Table 9

Table 9

PM1

PM0

Mode

Description

0

0

Normal

Mode

When operating in normal mode, all circuitry is fully powered up at all times.

0

1

Auto

Shutdown

When operating in auto shutdown mode, the AD7933/AD7934 will enter full shutdown mode at the end of

each conversion. In this mode, all circuitry is powered down.

1

0

Auto

Standby

When the AD7933/AD7934 enter this mode, all circuitry is partially powered down. This mode is similar to

the auto shutdown mode but it allows the part to power up in 1 µs.

1

1

Full

Shutdown

When the AD7933/AD7934 enters this mode, all circuitry is powered down. The information in the control

register is retained.

Rev. PrG | Page 16 of 32