AD5755-1x AD [Analog Devices], AD5755-1x Datasheet - Page 17

• Manufacturer Part Number: AD5755-1x
• Description: Quad Channel, 16-Bit, Serial Input, 4-20mA & Voltage Output DAC, Dynamic Power Control, HART Connectivity
• Manufacturer: AD [Analog Devices]

Preliminary Technical Data
SERIAL INTERFACE
The AD5755-1 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. Data coding is always straight binary.
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. Data is clocked in on the falling edge of
SCLK.
There are two ways in which the DAC outputs can be updated
as outlined below.
Individual DAC Updating
In this mode, LDAC is held low while data is being clocked into
the DAC Data Register. The addressed DAC output is updated
on the rising edge of SYNC .
Simultaneous Updating of All DACs
In this mode, LDAC is held high while data is being clocked
into the DAC Data Register. Only the first write to each
channels data register will be valid after LDAC is brought high.
Any subsequent writes while LDAC is still held high will be
ignored. All the DAC outputs are updated by taking LDAC low
any time after SYNC has been taken high.
Rev. PrD | Page 17 of 34
TRANSFER FUNCTION
Table 10 shows the input code to ideal output voltage
relationship for the AD5755-1 or straight binary data coding -
±10v output range shown.
Table 7. Ideal Output Voltage to Input Code Relationship
Digital Input
Straight Binary Data Coding
MSB
1111
1111
1000
0000
0000
Figure 16. Simplified Serial Interface of Input Loading Circuitryfor One DAC
1111
1111
0000
0000
0000
V
REFIN
LDAC
SYNC
SCLK
SDIN
1111
1111
0000
0000
0000
INTERFACE
REGISTER
REGISTER
16-BIT
DAC
INPUT
LOGIC
1111
1110
0000
0001
0000
DAC
Channel
LSB
I/V AMPLIFIER
Analog Output
V
+2 V
+2 V
0 V
−2 V
−2 V
OUT
OUTPUT
REF
REF
REF
REF
SDO
× (32767/32768)
× (32766/32768)
× (32766/32768)
× (32767/32768)
AD5755-1
V
OUT