SLAS986D November 2014 – February 2018 AMC7836
In the AMC7836 all-negative DAC range mode, each of the four DAC groups is set to a negative voltage output range (–5 to 0 V or –10 to 0 V).
Although the maximum DAC output does not exceed 0 V, the common AVCC voltage (AVCC = AVCC_AB = AVCC_CD) must still satisfy a minimum voltage of 4.7 V to comply with the device operating conditions. In this case a recommended approach is to tie the AVCC, AVDD, and DVDD supply pins to a common potential.
The minimum DAC output for each group cannot be lower than the voltage on the corresponding AVSS pins (AVEE, AVSSB, AVSSC, and AVSSD). The AVSS pins are not required to be tied to the same potential and typically the negative voltage at each AVSS pin is dictated by the desired operating DAC negative output range. One exception is the AVEE pin which must be the lowest potential in the device. The thermal pad should be either tied to the same potential as the AVEE pin or left disconnected. Table 6 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).||5 V|
|AVEE||AVEE must be the lowest potential in the device.
AVEE must be less than or equal to the minimum possible output voltage for DAC group A.
|AVEE ≤ –5 V
AVEE ≤ –10 V
|AVSSB, AVSSC, AVSSD||AVSSn must be less than or equal to the minimum possible output voltage for DAC group n (n = B, C, D).||AVEE ≤ AVSSn ≤ –5 V
AVEE ≤ AVSSn ≤ –10 V
|Thermal Pad||AVEE or,
After power-on or a reset event the output range for each DAC group is set automatically by the voltage present in the corresponding AVSS pin. In the all-negative DAC range mode all AVSS pins should be connected to a voltage lower than AVSSTH. If this condition is satisfied, all four DAC groups will initialize by default to the –10- to 0-V range. Because the negative clamp voltage is only dependent on the voltage in the AVSS pin, the default –10- to 0-V output range presents no risk even when the AVSS voltage is greater than –10 V. In this case the DAC group output should be modified to the –5 to 0 V range after initialization by setting the corresponding DAC range register (address 0x1E to 0x1F) to 101b.