
AD5791
Data Sheet
Rev. D | Page 22 of 28
Control Register
The control register controls the mode of operation of th
e AD5791.Table 11. Control Register
MSB
LSB
DB23
DB22
DB21
DB20
DB19…DB11
DB10
DB9
DB8
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
R/W
Register address
Control register data
R/
W
0
1
0
Reserved
LIN COMP
SDODIS
BIN/2sC
DACTRI
OPGND
RBUF
Reserved
Table 12. Control Register Functions
Clearcode Register
The clearcode register sets the value to which the DAC output is set when the CLR pin or CLR bit is asserted. The output value depends
on the DAC coding that is being used, either binary or twos complement. The default register value is 0.
Table 13. Clearcode Register
MSB
LSB
DB23
DB22
DB21
DB20
DB19
DB0
R/W
Register address
Clearcode register data
R/W
0
1
20-bits of data
Function
Description
Reserved
These bits are reserved and should be programmed to zero.
RBUF
Output amplifier configuration control.
0: internal amplifier, A1, is powered up and Resistor RFB and R1 are connected in series as shown in Figure 53. This allows an external amplifier to be connected in a gain of two configurations. See th
e AD5791 Features section for further details.
1: (default) internal amplifier, A1, is powered down and Resistor RFB and R1 are connected in parallel as shown in Figure 52 so that the resistance between the RFB and INV pins is 3.4 k, equal to the resistance of the DAC. This allows the RFB and INV pins to
be used for input bias current compensation for an external unity gain amplifier. See th
e AD5791 Features section for
further details.
OPGND
Output ground clamp control.
0: DAC output clamp to ground is removed and the DAC is placed in normal mode.
1: (default) DAC output is clamped to ground through a ~6 k resistance, and the DAC is placed in tristate mode.
Resetting the part puts the DAC in OPGND mode, where the output ground clamp is enabled and the DAC is tristated.
Setting the OPGND bit to 1 in the control register overrules any write to the DACTRI bit.
DACTRI
DAC tristate control.
0: DAC is in normal operating mode.
1: (default) DAC is in tristate mode.
BIN/2sC
DAC register coding select.
0: (default) DAC register uses twos complement coding.
1: DAC register uses offset binary coding.
SDODIS
SDO pin enable/disable control.
0: (default) SDO pin is enabled.
1: SDO pin is disabled (tristate).
LIN COMP
Linearity error compensation for varying reference input spans. See th
e AD5791 Features section for further details.
0
(Default) reference input span up to 10 V.
1
0
1
Reference input span between 10 V and 12 V.
1
0
1
0
Reference input span between 12 V and 16 V.
1
0
1
Reference input span between16 V and 19 V.
1
0
Reference input span between 19 V and 20 V.
R/W
Read/write select bit.