MAX5705 datasheet(20/26 Pages) MAXIM

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MAX5703/MAX5704/MAX5705

Ultra-Small, Single-Channel, 8-/10-/12-Bit Buffered Output

Voltage DACs with Internal Reference and SPI Interface

Maxim Integrated

REF Command

The REF (B[23:20] = 0010) command updates the global

reference setting used for the DAC. Set B[17:16] = 00 to

use an external reference for the DAC or set B[17:16] to

01, 10, or 11 to select either the 2.5V, 2.048V, or 4.096V

internal reference, respectively.

If RF3 (B19) is set to zero (default) in the REF command,

the REF I/O will not be driven by the internal reference

circuit, saving current. If RF3 is set to one, the REF I/O

will be driven by the internal reference circuit, consuming

an additional 25FA (typ) of current when the reference is

powered; when the reference is powered down, the REF

I/O will be high-impedance.

If RF2 (B18) is set to zero (default) in the REF command,

the reference will be powered down any time the DAC

is powered down (in STANDBY mode). If RF2 (B18) is

set to one, the reference will remain powered even if the

DAC is powered down, allowing continued operation of

external circuitry. In this mode, the 1FA shutdown state is

not available. See Table 3.

SOFTWARE Commands

The SOFTWARE (B[23:20] = 0011) commands provide

a means of issuing several flexible software actions. See

Table 4.

The SOFTWARE Command Action Mode is selected by

B[18:16]:

END (000):

Used to end any active gate operation,

returning to normal operation (default).

GATE (001):

DAC contents will be gated to their

DEFAULT selected values until the gate

condition is removed.

CLEAR (100):

All CODE and DAC contents will be

cleared to their DEFAULT selected

values.

RESET (101):

All

CODE,

DAC,

RETURN,

and

configuration registers reset to their

power-up defaults (including REF,

POWER,

and

CONFIG

settings),

simulating a power cycle reset.

OTHER:

No effect.

Table 3. REF (0010) Command Format

Table 4. SOFTWARE (0011) Command Format

B23 B22 B21 B20 B19 B18 B17 B16 B15 B14 B13 B12 B11 B10 B9

B8 B7 B6 B5 B4 B3 B2 B1 B0

RF3 RF2 RF1 RF0 X

REF COMMAND

Ref Mode:

00 = EXT

01 = 2.5V

10 = 2.0V

11 = 4.0V

Don’t Care

DEFAULT VALUES

COMMAND BYTE

DATA HIGH BYTE

DATA LOW BYTE

B23 B22 B21 B20 B19 B18 B17 B16 B15 B14 B13 B12 B11 B10 B9

B8 B7 B6

B3 B2

SW2 SW1 SW0 X

SOFTWARE

COMMANDS

Mode:

000: END

001: GATE

100: CLR

101: RST

Other: No

Effect

Don’t Care

DEFAULT VALUES

COMMAND BYTE

DATA HIGH BYTE

DATA LOW BYTE

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