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(2)
REFERENCE VOLTAGE SOURCE
The ADN8810 is designed to operate with a 4.096 V reference
voltage connected to VREF. The output current is directly
proportional to this reference voltage. A low noise precision
reference should be used to achieve the best performance. The
ADR292, ADR392, or REF198 is recommended.
POWER SUPPLIES
There are three principal supply current paths through the
ADN8810:
?   AVDD provides power to the analog front end of the
ADN8810 including the DAC. Use this supply line to
power the external voltage reference. For best performance,
AVDD should be low noise.
?   DVDD provides power for the digital circuitry. This
includes the serial interface logic, the
SB
and
RESET
logic
inputs, and the FAULT output. Tie DVDD to the same
supply line used for other digital circuitry. It is not
necessary for DVDD to be low noise.
?   PVDD is the power pin for the output amplifier. It can
operate from as low as 3.0 V to minimize power dissipation
in the ADN8810. For best performance, PVDD should be
low noise.
Current is returned through three pins:
?   AVSS is the return path for both AVDD and PVDD. This
pin is connected to the substrate of the die as well as the
slug on the bottom of the LFCSP package. For single-
supply operation, this pin should be connected to a low
noise ground plane.
?   DVSS returns current from the digital circuitry powered by
DVDD. Connect DVSS to the same ground line or plane
used for other digital devices in the application.
?   DGND is the ground reference for the digital circuitry. In a
single-supply application, connect DGND to DVSS.
For single-supply operation, set AVDD to 5 V, set PVDD from
3.0 V to 5 V, and connect AVSS, AGND, and DGND to ground.
SERIAL DATA INTERFACE
The ADN8810 uses a serial peripheral interface (SPI) with three
input signals: SDI, CLK, and
CS
. Figure 2 shows the timing
diagram for these signals.
Data applied to the SDI pin is clocked into the input shift
register on the rising edge of CLK. After all 16 bits of the data-
word have been clocked into the input shift register, a logic high
on CS
loads the shift register byte into the ADN8810. If more
than 16 bits of data are clocked into the shift register before
CS
goes high, bits will be pushed out of the register in first-in first-
out (FIFO) fashion.
The four most significant bits (MSB) of the data byte are
checked against the devices address. If they match, the next 12
bits of the data byte are loaded into the DAC to set the output
current. The first bit (MSB) of the data byte must be a logic zero,
and the following three bits must correspond to the logic levels
on pins ADDR2, ADDR1, and ADDR0, respectively, for the