LTC1669 LINER [Linear Technology], LTC1669 Datasheet - Page 9

• Manufacturer Part Number: LTC1669
• Description: 10-Bit Rail-to-Rail Micropower DAC with I2C Interface
• Manufacturer: LINER [Linear Technology]

APPLICATIONS
SYNC Address/Quick Command
In addition to the slave address, the LTC1669 has an
address that can be shared by other devices so that they
may be updated synchronously. The address is called to
the SYNC address and uses the quick command protocol.
The SYNC Address is 1111 110
The SY/CLR bit set high only has meaning when the “SY”
bit of the command byte was previously set HIGH. On the
otherhand, the SY/CLR bit set LOW will always clear the
part, independent of the state of the “SY” bit in the
command byte.
Voltage Output
The output amplifier contained in the LTC1669 can source
or sink up to 5mA. The output stage swings to within a few
millivolts of either supply rail when unloaded and has an
equivalent output resistance of 85 when driving a load to
the rails. The output amplifier is 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 greater
than 1000pF. For example, a 0.1 F load can be driven by
the LTC1669 if a 110 series resistance is used. The phase
margin of the resulting circuit is 45 and increases mono-
tonically from this point if larger values of resistance, ca-
pacitance or both are substituted for the values given.
SY/CLR
1
0
Start
1
Update output latches on rising edge of SCL during
Acknowledge of SYNC Address
Clear all internal latches on rising edge of SCL during
Acknowledge of SYNC Address
SYNC Address
1111 110
U
7
INFORMATION
U
SY/CLR
1
Ack
1
W
Stop
1669 TA05
1
U
Rail-to-Rail Output Considerations
As in any rail-to-rail device, 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 1b.
Similarly, limiting can occur near full scale when V
used as the reference. If V
error (FSE) is positive, the output for the highest codes
limits at V
can occur if the internal reference is used.
Offset and linearity are defined and tested over the region
of the DAC transfer function where no output limiting can
occur.
Internal Reference
In applications where a predictable output is required that
is independent of supply voltage, the LTC1669 has a user-
selectable internal reference. Selecting the internal refer-
ence will set the full-scale output voltage to 2.5V. This can
be useful in applications where the supply voltage is
poorly regulated.
Using the LT
Power Supply for the LTC1669
In applications where the advantages of using the internal
reference are required but the full-scale range needs to be
greater than 2.5V, an external series reference can be
used. The LT1460 is ideal for use as a power supply for the
LTC1669 and can provide 3V, 3.3V and 5V full-scale
output voltage ranges. The LT1460 provides accuracy,
noise immunity and extended supply range to the LTC1669
when the LTC1669 is operated ratiometric to V
both parts are available in SOT-23 packages, the PC board
space for this application is extremely small. See Figure 2.
CC
as shown in Figure 1c. No full-scale limiting
®
1460 Micropower Series Reference as a
REF
= V
CC
and the DAC full-scale
LTC1669
CC
. Since
CC
9
1669f
is