LTC1665_15 Datasheet, PDF (11/18 Pages) Linear Technology – Micropower Octal 8-Bit and 10-Bit DACs

LTC1665/LTC1660
OPERATION
Table 2. DAC Address/Control Functions
ADDRESS/CONTROL
A3 A2 A1 A0 DAC STATUS
0
0
0
0
No Change
0
0
0
1
Load DAC A
0
0
1
0
Load DAC B
0
0
1
1
Load DAC C
0
1
0
0
Load DAC D
0
1
0
1
Load DAC E
0
1
1
0
Load DAC F
0
1
1
1
Load DAC G
1
0
0
0
Load DAC H
1
0
0
1
No Change
1
0
1
0
No Change
1
0
1
1
No Change
1
1
0
0
No Change
1
1
0
1
No Change
1
1
1
0
No Change
1
1
1
1 Load ALL DACs
with Same
8/10-Bit Code
SLEEP STATUS
Wake
Wake
Wake
Wake
Wake
Wake
Wake
Wake
Wake
Wake
Wake
Wake
Wake
Wake
Sleep
Wake
Sleep mode is initiated by performing a load sequence
to address 1110_b (the DAC input word D7-D0 [D9-D0]
is ignored). Once in Sleep mode, a load sequence to any
other address (including “No Change” addresses 0000_b
and 1001-1101_b) causes the LTC1665/LTC1660 to Wake.
It is possible to keep one or more chips of a daisy chain
in continuous Sleep mode by giving the Sleep instruction
to these chips each time the active chips in the chain are
updated.
Voltage Outputs
Each of the eight rail-to-rail output amplifiers contained
in these parts can source or sink up to 5mA. The outputs
swing to within a few millivolts of either supply rail when
unloaded and have an equivalent output resistance of 85Ω
when driving a load to the rails. The output amplifiers are
stable driving capacitive loads up to 1000pF.
A small resistor placed in series with the output can be
used to achieve stability for any load capacitance. A 1μF
load can be successfully driven by inserting a 20Ω resis-
tor; a 2.2μF load needs only a 10Ω resistor. In either case,
larger values of resistance, capacitance or both may be
safely substituted for the values given.
Rail-to-Rail Output Considerations
In any rail-to-rail output voltage DAC, the output is limited
to voltages within the supply range.
If the DAC offset is negative, the output for the lowest
codes limits at 0V as shown in Figure 3b.
Similarly, limiting can occur near full scale when the REF
pin is tied to V_CC. If V_REF = V_CC and the DAC full-scale error
(FSE) is positive, the output for the highest codes limits
at V_CC as shown in Figure 3c. No full-scale limiting can
occur if V_REF is less than V_CC – FSE.
Offset and linearity are defined and tested over the region
of the DAC transfer function where no output limiting
can occur.
166560fa
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