AD5381BST-3 Analog Devices Inc, AD5381BST-3 Datasheet - Page 27

• Manufacturer Part Number: AD5381BST-3
• Description: IC DAC 12BIT 40CH 3V 100-LQFP
• Manufacturer: Analog Devices Inc

Specifications of AD5381BST-3

• Design Resources: 40 Channels of Programmable Voltage with Excellent Temperature Drift Performance Using AD5381 (CN0010) AD5381 Channel Monitor Function (CN0013)
• Settling Time: 6µs
• Number Of Bits: 12
• Data Interface: Serial, Parallel
• Number Of Converters: 40
• Voltage Supply Source: Single Supply
• Power Dissipation (max): 80mW
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 100-LQFP
• For Use With: EVAL-AD5381EB - BOARD EVAL FOR AD5381
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Daisy-Chain Mode
For systems that contain several devices, the SDO pin can be
used to daisy-chain several devices together. This daisy-chain
mode can be useful in system diagnostics and in reducing the
number of serial interface lines.
By connecting the DCEN (daisy-chain enable) pin high, daisy-
chain mode is enabled. The first falling edge of SYNC starts the
write cycle. The SCLK is continuously applied to the input shift
register when SYNC is low. If more than 24 clock pulses are
applied, the data ripples out of the shift register and appears
on the SDO line. This data is clocked out on the rising edge of
SCLK and is valid on the falling edge. By connecting the SDO
of the first device to the DIN input on the next device in the
chain, a multidevice interface is constructed. Twenty-four clock
pulses are required for each device in the system. Therefore, the
total number of clock cycles must equal 24N, where N is the
total number of AD538x devices in the chain.
When the serial transfer to all devices is complete, SYNC is
taken high. This latches the input data in each device in the
daisy-chain and prevents further data from being clocked
into the input shift register.
If SYNC is taken high before 24 clocks are clocked into the part,
this is considered a bad frame and the data is discarded.
The serial clock can be either a continuous or a gated clock. A
continuous SCLK source can only be used if it can be arranged
that SYNC is held low for the correct number of clock cycles. In
gated clock mode, a burst clock containing the exact number of
clock cycles must be used and SYNC must be taken high after
the final clock to latch the data.
SYNC
SCLK
SDO
DIN
INPUT WORD SPECIFIES REGISTER TO BE READ
DB23
DB23
UNDEFINED
Figure 30. Serial Readback Operation
24
DB0
DB0
Rev. B | Page 27 of 40
DB23
DB23
SELECTED REGISTER DATA CLOCKED OUT
Readback Mode
Readback mode is invoked by setting the R/ W bit = 1 in the
serial input register write. With R/ W = 1, Bits A5 to A0, in
association with Bits REG1 and REG0, select the register to be
read. The remaining data bits in the write sequence are don’t
cares. During the next SPI write, the data appearing on the
SDO output will contain the data from the previously
addressed register.
For a read of a single register, the NOP command can be used
in clocking out the data from the selected register on SDO.
Figure 30 shows the readback sequence. For example, to read
back the m register of Channel 0 on the AD5381, the following
sequence should be implemented. First, write 0x404XXX to the
AD5381 input register. This configures the AD5381 for read
mode with the m register of Channel 0 selected. Note that Data
Bits DB11 to DB0 are don’t cares. Follow this with a second
write, a NOP condition, 0x000000.
During this write, the data from the m register is clocked out on
the DOUT line, that is, data clocked out will contain the data
from the m register in Bit DB11 to Bit DB0, and the top 10 bits
contain the address information as previously written. In
readback mode, the SYNC signal must frame the data. Data is
clocked out on the rising edge of SCLK and is valid on the
falling edge of the SCLK signal. If the SCLK idles high between
the write and read operations of a readback operation, the first
bit of data is clocked out on the falling edge of SYNC .
NOP CONDITION
48
DB0
DB0
AD5381