Datasheet

AD5791 Data Sheet
Rev. D | Page 22 of 28
Control Register
The control register controls the mode of operation of the 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 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 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 R
FB
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 the AD5791 Features section for further details.
1: (default) internal amplifier, A1, is powered down and Resistor R
FB
and R1 are connected in parallel as shown in Figure 52 so
that the resistance between the R
FB
and INV pins is 3.4 kΩ, equal to the resistance of the DAC. This allows the R
FB
and INV pins to
be used for input bias current compensation for an external unity gain amplifier. See the 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 kΩ 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 the AD5791 Features section for further details.
0 0 0 0 (Default) reference input span up to 10 V.
1 0 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 1 Reference input span between16 V and 19 V.
1 1 0 0 Reference input span between 19 V and 20 V.
R/
W
Read/write select bit.
0: AD5791 is addressed for a write operation.
1: AD5791 is addressed for a read operation.