SLAS986D November 2014 – February 2018 AMC7836
In the AMC7836 all-positive DAC range mode, each of the four DAC groups is set to a positive voltage output range (0 to 5 V or 0 to 10 V).
Because the maximum DAC output for each group cannot exceed the common AVCC voltage for the device (AVCC = AVCC_AB = AVCC_CD), a DAC group in the 0 to 10 V output range forces the AVCC voltage to a value greater or equal to 10 V even if the remaining DAC groups are set in the 0 to 5 V range. If all DAC groups are set in the 0 to 5 V range the AVCC voltage can be set to a value as low as 5 V.
The minimum DAC output for each group cannot be lower than the AVSS voltage but because the minimum DAC output is 0 V in the all-positive DAC range mode, all of the AVSS pins (AVEE, AVSSB, AVSSC, and AVSSD) as well as the device thermal pad can be tied to AGND thus simplifying the board design. Table 5 lists the typical configurations for this mode.
|DVDD||DVDD must be equal to AVDD.||5 V|
|IOVDD||IOVDD must be equal to or less than DVDD.||1.8 V to 5 V|
|AVCC_AB, AVCC_CD||The AVCC_AB and AVCC_CD pins must be tied to the same potential (AVCC).
AVCC must be greater or equal than the maximum possible output voltage for any of the sixteen DACs.
|AVCC ≥ 5 V
AVCC ≥ 10 V
|AVSSB, AVSSC, AVSSD||AGND|
After power-on or a reset event the output range for each DAC group is set automatically by the voltage present on the corresponding AVSS pin. In the all-positive DAC range mode all AVSS pins are connected to AGND and consequently all four DAC groups will initialize by default to the 0 to 5 V range. The output for any of the DAC groups can be modified to the 0 to 10 V range after initialization by setting the corresponding DAC range register (address 0x1E to 0x1F) to 110b.
In addition to setting the default output range, the AVSS pins also set the clamp voltage for each DAC group. Because the clamp voltage is only dependent on the voltage in the AVSS pin, changes to the DAC range registers do not affect the clamp setting. With the AVSS pins connected to AGND, the clamp voltage for all sixteen DACs is 0 V.