AD5421_11 AD [Analog Devices], AD5421_11 Datasheet - Page 25

• Manufacturer Part Number: AD5421_11
• Description: 16-Bit, Serial Input, Loop-Powered, 4 mA to 20 mA DAC
• Manufacturer: AD [Analog Devices]

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
4 mA to 20 mA Range
4
4.00024
…
11.9997
12
…
19.9995
19.9997
D11
D10
D9
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D8
16-bit data
3.8 mA to 21 mA Range
3.8
3.80026
…
12.39974
12.4
…
20.99947
20.99974
D7
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
D1
AD5421
LSB
D0