SLAS986D November 2014 – February 2018 AMC7836
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 (AVEE, AVSSB, AVSSC or AVSSD). When the AVSS voltage of a DAC group is lower than the threshold value, AVSSTH, the output for that DAC group is automatically configured to the –10 to 0 V range. Conversely, if the DAC group AVSS voltage is higher than AVSSTH, the DAC-group output is automatically set to the 0 to 5 V range. The auto-range detector results for each DAC group are stored in the general status register (address 0x72).
In addition to a power-on or reset event, the auto-range detector is also enabled by a register write to the DAC power down registers (address 0xB2 through 0xB3) or the device configuration register (address 0x02).
Although the initial output-range setting is determined by the auto-range detector, the output range for each DAC-group can be afterwards configured to any of the available output ranges (–10 to 0 V, –5 to 0 V, 0 to 5 V, or 0 to 10 V) through the DAC range registers (address 0x1E through 0x1F).
The power-on-reset and clamp-voltage value of each DAC group is set by the corresponding AVSS pin and is independent of the DAC output range. In some applications, matching the clamp-voltage setting to the operating voltage range is imperative. For those applications, the recommended connections for the AVSS pin are: AGND for the positive output ranges, in which case the clamp voltage is 0 V; a negative supply voltage with a lower value than the minimum DAC output voltage (–5 V or –10 V) for the selected negative output range, in which case the unloaded clamp voltage is determined by the value of the negative supply voltage (see Figure 50).
Although not a recommended operating condition, the device allows a DAC group to operate in a positive output range even if its clamp voltage is negative (AVSS connected to a negative supply voltage).
A special distinction must be made for DAC group A as the AVSS pin of this group is the dual-function AVEE pin. Aside from setting the clamp voltage and default output range for the DAC group A, the AVEE pin is also the lowest potential in the device. As a consequence the AVEE voltage is dependent on the other AVSS pin connections. The AVEE pin can only be connected to the analog ground if all the other AVSS pins are also connected to the analog ground. If any of the AVSS pins is connected to a negative voltage, the AVEE pin must also be connected to that voltage (see Table 1).
The full-scale output range for each DAC group is limited by the corresponding AVCC and AVSS values. The maximum and minimum outputs cannot exceed the AVCC voltage or be lower than the AVSS voltage, respectively.
|DAC GROUP||DAC||AUTO-RANGE AND CLAMP VOLTAGE SELECTION (AVSS)||AVEE = AGND||AVEE = VNEG|
|OUTPUT RANGE||CLAMP VOLTAGE CONNECTION||OUTPUT RANGE||CLAMP VOLTAGE CONNECTION|
|A||DAC_A0||AVEE||0 to 5 V or 0 to 10 V||AGND||–5 to 0 V or –10 to 0 V||VNEG|
|B||DAC_B4||AVSSB||0 to 5 V or 0 to 10 V||AGND||–5 to 0 V or –10 to 0 V||VNEG ≤ AVSSB ≤ –5 V|
|DAC_B6||0 to 5 V or 0 to 10 V||AGND|
|C||DAC_C8||AVSSC||0 to 5 V or 0 to 10 V||AGND||–5 to 0 V or –10 to 0 V||VNEG ≤ AVSSC ≤ –5 V|
|DAC_C10||0 to 5 V or 0 to 10 V||AGND|
|D||DAC_D12||AVSSD||0 to 5 V or 0 to 10 V||AGND||–5 to 0 V or –10 to 0 V||VNEG ≤ AVSSD ≤ –5 V|
|DAC_D14||0 to 5 V or 0 to 10 V||AGND|