AMC7836_15 Datasheet, PDF (41/87 Pages) Texas Instruments – AMC7836 High-Density, 12-Bit Analog Monitor and Control Solution With Multichannel ADC, Bipolar DACs, Temperature Sensor, and GPIO Ports

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AMC7836
SLAS986B – NOVEMBER 2014 – REVISED FEBRUARY 2015
7.4.3 Mixed DAC Range Mode
In the AMC7836 mixed DAC range mode, a combination of DAC groups is set to a negative voltage output range
(–5 to 0 V or –10 to 0 V) and 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 AV_CC voltage for the device
(AV_CC = AV_{CC_AB} = AV_{CC_CD}), a DAC group in the 0 to 10 V output range forces the AV_CC voltage to a value
greater or equal to 10 V. If all positive DAC groups are in the 0 to 5 V range the AV_CC voltage can be set to a
value as low as 5 V.
The minimum DAC output for each group cannot be lower than the voltage on the corresponding AV_SS pins
(AV_EE, AV_SSB, AV_SSC and AV_SSD). The AV_SS pins are not required to be tied to the same potential and typically
the negative voltage at each AV_SS pin is dictated by the desired operating DAC negative output range. One
exception is the AV_EE pin which must be the lowest potential in the device. The implication of this requirement is
that if either DAC group B, C or D is set to a negative output range, DAC group A must also be set to a negative
range. The thermal pad should be either tied to the same potential as the AV_EE pin or left disconnected. Table 7
lists the typical configurations for this mode.
PIN
AV_DD
DV_DD
IOV_DD
AV_{CC_AB}, AV_{CC_CD}
AV_EE
AV_SSB, AV_SSC, AV_SSD
Thermal Pad
Table 7. Mixed DAC Range Mode Typical Configuration
NOTES
DV_DD must be equal to AV_DD.
IOV_DD must be equal to or less than DV_DD.
The AV_{CC_AB} and AV_{CC_CD} pins must be tied to the
same potential (AV_CC).
AV_CC must be greater or equal to the maximum
possible output voltage for any of the positive
output range DACs.
AVEE must be the lowest potential in the device.
AV_EE must be less than or equal to the minimum
possible output voltage for DAC group A.
TYPICAL CONNECTION
5V
5V
1.8 V to 5 V
AV_CC ≥ 5 V
AV_CC ≥ 10 V
AVEE ≤ –5 V
AVEE ≤ –10 V
AV_SSn must be less than or equal than the minimum _{Negative Range}
possible output voltage for DAC group n (n = B, C,
D).
Positive Range
AV_EE or,
Floating
AV_EE ≤ AV_SSn ≤ –5 V
AV_EE ≤ AV_SSn ≤ –10 V
AGND
After power-on or a reset event the output range for each DAC group is set automatically by the voltage present
in the corresponding AV_SS pin. When the AV_SS voltage of a DAC group is lower than the threshold value, AV_SSTH,
the output for that DAC group is automatically configured to the –10 to 0 V range. Conversely, if the AV_SS voltage
of the DAC group is higher than AV_SSTH, the DAC-group output is automatically set to the 0 to 5 V range. The
output for any of the DAC groups can be modified after initialization by setting the corresponding DAC range
register (address 0x1E to 0x1F).
In addition to setting the default output range, the AV_SS pins also set the clamp voltage for each DAC group.
Because the clamp voltage is only dependent on the voltage in the AV_SS pin, changes to the DAC range
registers do not affect the clamp setting.
NOTE
Although not a recommended operating condition, the device allows a DAC group to
operate in a positive output range even if the clamp voltage is negative (AV_SS connected
to a negative supply voltage).
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