AD5764ASU-REEL7 Analog Devices Inc, AD5764ASU-REEL7 Datasheet - Page 18

• Manufacturer Part Number: AD5764ASU-REEL7
• Description: IC DAC 16BIT QUAD VOUT 32TQFP
• Manufacturer: Analog Devices Inc

Specifications of AD5764ASU-REEL7

• Design Resources: High Accuracy, Bipolar Voltage Output Digital-to-Analog Conversion Using AD5764 (CN0006)
• Settling Time: 8µs
• Number Of Bits: 16
• Data Interface: Serial
• Number Of Converters: 4
• Voltage Supply Source: Dual ±
• Power Dissipation (max): 275mW
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFP, 32-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD5764
THEORY OF OPERATION
The AD5764 is a quad, 16-bit, serial input, bipolar voltage output
DAC and operates from supply voltages of ±11.4 V to ±16.5 V and
has a buffered output voltage of up to ±10.5263 V. Data is written to
the AD5764 in a 24-bit word format, via a 3-wire serial interface.
The device also offers an SDO pin that is available for daisy-
chaining or readback.
The AD5764 incorporates a power-on reset circuit, which ensures
that the data register powers up loaded with 0x0000. The AD5764
features a digital I/O port that can be programmed via the serial
interface, on-chip reference buffers and per channel digital gain,
and offset registers.
DAC ARCHITECTURE
The DAC architecture of the AD5764 consists of a 16-bit,
current mode, segmented R-2R DAC. The simplified circuit
diagram for the DAC section is shown in Figure 32.
The four MSBs of the 16-bit data word are decoded to drive
15 switches, E1 to E15. Each of these switches connects one of
the 15 matched resistors to either AGNDx or IOUT. The remain-
ing 12 bits of the data-word drive Switch S0 to Switch S11 of
the 12-bit R-2R ladder network.
REFERENCE BUFFERS
The AD5764 operates with an external reference. The reference
inputs (REFAB and REFCD) have an input range up to 7 V. This
input voltage is used to provide a buffered positive and negative
reference for the DAC cores. The positive reference is given by
The negative reference to the DAC cores is given by
These positive and negative reference voltages (along with the
gain register values) define the output ranges of the DACs.
V
REF
E15
2R
4 MSBs DECODED INTO
+V
−V
15 EQUAL SEGMENTS
REF
REF
E14
2R
= 2 × V
= −2 × V
E1
REF
Figure 32. DAC Ladder Structure
REF
2R
R
S11
12-BIT, R-2R LADDER
2R
R
S10
2R
R
S0
2R
2R
AGNDx
IOUT
R/8
VOUTx
Rev. D | Page 18 of 28
SERIAL INTERFACE
The AD5764 is controlled over a versatile 3-wire serial interface
that operates at clock rates of up to 30 MHz and is compatible
with SPI, QSPI™, MICROWIRE™, and DSP standards.
Input Shift Register
The input shift register is 24 bits wide. Data is loaded into the
device MSB first as a 24-bit word under the control of a serial
clock input, SCLK. The input shift register consists of a read/
write bit, three register select bits, three DAC address bits, and
16 data bits, as shown in Table 9. The timing diagram for this
operation is shown in Figure 2.
Upon power-up, the data register is loaded with zero code
(0x0000), and the outputs are clamped to 0 V via a low imped-
ance path. The outputs can be updated with the zero code value
at this time by asserting either LDAC or CLR . The corresponding
output voltage depends on the state of the BIN/ 2sCOMP pin. If
the BIN/ 2sCOMP pin is tied to DGND, the data coding is twos
complement, and the outputs update to 0 V. If the BIN/ 2sCOMP
pin is tied to DV
outputs update to negative full scale. To power up the outputs
with zero code loaded to the outputs, hold the CLR pin low
during power-up.
Standalone Operation
The serial interface works with both a continuous and noncon-
tinuous serial clock. A continuous SCLK source can only be
used if 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. The first falling edge of SYNC
starts the write cycle. Exactly 24 falling clock edges must be
applied to SCLK before SYNC is brought high again. If SYNC is
brought high before the 24
is invalid. If more than 24 falling SCLK edges are applied before
SYNC is brought high, the input data is also invalid. The input
shift register addressed is updated on the rising edge of SYNC .
For another serial transfer to take place, SYNC must be brought
low again. After the end of the serial data transfer, data is
automatically transferred from the input shift register to the
addressed register.
When the data has been transferred into the chosen register of
the addressed DAC, the data register and outputs can be
updated by taking LDAC low.
CC
, the data coding is offset binary, and the
th
falling SCLK edge, the data written