AD5421 Analog Devices, AD5421 Datasheet - Page 30

• 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
Transfer Function Equations with Offset and Gain Adjust
Values
When the offset adjust and gain adjust register values are taken
into account, the transfer equations can be expressed as follows.
For the 4 mA to 20 mA output range, the loop current can be
expressed as follows:
For the 3.8 mA to 21 mA output range, the loop current can be
expressed as follows:
I
+
I
+
LOOP
LOOP








4
3
8 .
mA
=
=
mA















 

+

 

16
17
+



2
2 .

 

2
mA
16



16
16

 

mA
2
17
2
mA
2
16

 

16
16
2 .
2
×

 

16
mA
×

 

Gain
×
Gain

 

(
Offset
×
×
(
×
Offset
D







D
−







32
−
,
768
32
,
768
)







)







Rev. C | Page 30 of 36
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.
Gain is the decimal value of the gain adjust register.
Offset is the decimal value of the offset adjust register.
Note that the offset adjust register cannot adjust the zero-scale
output value downward.
I
+
LOOP




3
2 .
=
mA








 

+
20
8 .
2




 

16
mA
20
2
8 .
2
16

 

16
mA
×
Gain

 

×
(
Offset
×
D







−
32
Data Sheet
,
768
)






