Data Sheet

AD5781

Rev. D | Page 21 of 28

Table 9. Hardware Control Pins Truth Table

LDAC

CLR

RESET

Function

X1

X1

0

The AD5781 is in reset mode. The device cannot be programmed.

X1

X1

The AD5781 is returned to its power-on state. All registers are set to their default values.

0

0

1

The DAC register is loaded with the clearcode register value, and the output is set accordingly.

0

1

1

The output is set according to the DAC register value.

1

0

1

The DAC register is loaded with the clearcode register value, and the output is set accordingly.

1

1

The output is set according to the DAC register value.

0

1

The output remains at the clear code value.

1

1

The output remains set according to the DAC register value.

0

1

The output remains at the clear code value.

1

1

The DAC register is loaded with the clearcode register value and the output is set accordingly.

0

1

The DAC register is loaded with the clearcode register value and the output is set accordingly.

1

1

The output remains at the clear code value.

0

1

The output is set according to the DAC register value.

1

X is don’t care.

ON-CHIP REGISTERS

DAC Register

Table 10 outlines how data is written to and read from the DAC register.

Table 10. DAC Register

MSB

LSB

DB23

DB22

DB21

DB20

DB19

DB2

DB1

DB0

R/W

Register address

DAC register data

R/W

0

0

1

18-bits of data

X1

X1

1

X is don’t care.

The following equation describes the ideal transfer function of the DAC:

(

)

REFN

REFN

REFP

OUT

V

D

V

V

V

+

−

×

−

=

1

where:

D is the 18-bit code programmed to the DAC.