2-Wire Serial 8-Bit DACs with

Rail-to-Rail Outputs

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11

Furthermore if the transmission’s last command byte

has PD high, the output latches are updated, but volt-

age outputs will not reflect the newly entered data

because the DAC enters power-down mode when the

STOP condition is detected. When in power-down, the

DAC outputs float. In this mode, the supply current is a

maximum of 20µA. A command byte with the PD bit low

returns the MAX517/MAX518/MAX519 to normal opera-

tion following a STOP condition, with the voltage out-

puts reflecting the output-latch contents (Figures 10a

and 10b). Because each subsequent command byte

overwrites the previous PD bit, only the last command

byte of a transmission affects the power-down state.

Setting the RST bit high clears the DAC input latches.

The DAC outputs remain unchanged until a STOP con-

dition is detected (Figure 11a). If a reset is issued, the

following output byte is ignored. Subsequent pairs of

command/output bytes overwrite the input latches

(Figure 11b).

All changes made during a transmission affect the

MAX517/MAX518/MAX519’s outputs only when the

transmission ends and a STOP has been recognized.

The R0, R1, and R2 bits are reserved and must be set

to zero.

The MAX517/MAX518/MAX519 are fully compatible

impedance inputs; SDA has an open drain that pulls

the data line low during the 9th clock pulse. Figure 12

(

)

(

)

(

)

SDA

0

START

CONDITION

ADDRESS BYTE

ACK

10

1

or

AD3

1

or

AD2 AD1AD0 0

0

0 0010

0

(RST)

(RST)

STOP

CONDITION

COMMAND BYTE

ACK

ALL OUTPUTS

SET TO 0.

(

)

ALL INPUT LATCHES

SET TO 0.

ALL INPUT LATCHES

SET TO 0.

SDA

0

START

CONDITION

ADDRESS BYTE

ACK

10

1

or

AD3

1

or

AD2 AD1 AD0 0

0 00010

0

0

STOP

CONDITION

COMMAND BYTE

ACK

"DUMMY"

OUTPUT BYTE

ACK

(a)

(b)

DAC OUTPUTS SET TO 0 UNLESS

CHANGED BY ADDITIONAL COMMAND

BYTE/OUTPUT BYTE PAIRS.

NOTE: X = DON'T CARE

ADDITIONAL

COMMAND BYTE/

OUTPUT BYTE PAIRS

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Figure 11. Resetting DAC Outputs

(

)

SDA

0

START

CONDITION

ADDRESS BYTE

ACK

10

1

or

AD3

1

or

AD2 AD1 AD0 0

0

0

0 0000

(PD)

(PD)

STOP

CONDITION

COMMAND BYTE

ACK

DEVICE RETURNS TO

NORMAL OPERATION

(

)

DAC0 INPUT

LATCH SET TO 0.

SDA

0

START

CONDITION

ADDRESS BYTE

ACK

10

1

or

AD3

1

or

AD2AD1 AD0 0

0

0

0000

0

0

0

0

0

00

00

00

STOP

CONDITION

COMMAND BYTE

(ADDRESSING DAC0)

ACK

OUTPUT BYTE

(SET TO 0)

ACK

(a)

(b)

DEVICE RETURNS TO NORMAL OPERATION.

DAC0 SET TO 0.

NOTE: X = DON'T CARE

X

X

X

X

X

(

)

Figure 10. Returning to Normal Operation from Power-Down