AD5421 Analog Devices, AD5421 Datasheet - Page 26

• Manufacturer Part Number: AD5421
• Description: 16-Bit, Serial Input, Loop-Powered, 4mA to 20mA DAC
• Manufacturer: Analog Devices

Specifications of AD5421

• Resolution (bits): 16bit
• Dac Settling Time: 50µs
• Max Pos Supply (v): +52V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: SPI

AD5421
DAC REGISTER
The DAC register is a read/write register and is addressed
as described in Table 11. The data programmed to the DAC
register determines the loop current, as shown in the Ideal
Output Transfer Function section and in Table 15.
Ideal Output Transfer Function
The transfer function describing the relationship between the
data programmed to the DAC register and the loop current is
expressed by the following three equations.
For the 4 mA to 20 mA output range, the loop current can be
expressed as follows:
Table 14. DAC Register Bit Map
MSB
D15
Table 15. Relationship of DAC Register Code to Ideal Loop Current (Gain = 65,536; Offset = 0)
DAC Register Code
0x0000
0x0001
…
0x7FFF
0x8000
…
0xFFFE
0xFFFF
I
LOOP
D14
=

 

16
D13
2
mA
16

 

×
D12
D
+
4
mA
D11
4 mA to 20 mA Range
4
4.00024
…
11.9997
12
…
19.9995
19.9997
D10
D9
Rev. C | Page 26 of 36
D8
16-bit data
D7
3.8 mA to 21 mA Range
3.8
3.80026
…
12.39974
12.4
…
20.99947
20.99974
For the 3.8 mA to 21 mA output range, the loop current can be
expressed as follows:
For the 3.2 mA to 24 mA output range, the loop current can be
expressed as follows:
where D is the decimal value of the DAC register.
Ideal Loop Current (mA)
I
I
D6
LOOP
LOOP
=
=
D5

 


 

17
20
2 .
8 .
2
2
16
16
mA
mA
D4

 


 

×
×
D
D
3.2 mA to 24 mA Range
3.2
3.2003
…
13.5997
13.6
…
23.9994
23.9997
+
+
D3
3
3
8 .
2 .
mA
mA
D2
Data Sheet
D1
LSB
D0