DAC7641Y Burr-Brown Corporation, DAC7641Y Datasheet - Page 18

• Manufacturer Part Number: DAC7641Y
• Description: 16-Bit/ Voltage Output DIGITAL-TO-ANALOG CONVERTER
• Manufacturer: Burr-Brown Corporation

DIGITALLY-PROGRAMMABLE
CURRENT SOURCE
The DAC7641 offers a unique set of features that allows a
wide range of flexibility in designing applications circuits
such as programmable current sources. The DAC7641 offers
both a differential reference input as well as an open-loop
configuration around the output amplifier. The open-loop
configuration around the output amplifier allows transistor
to be placed within the loop to implement a digitally-
programmable, uni-directional current source. The availabil-
ity of a differential reference also allows programmability
for both the full-scale and zero-scale currents. The output
current is calculated as:
FIGURE 15. 4-to-20mA Digitally Controlled Current Source.
I
OUT
®
DAC7641
1000pF
1000pF
V
REF
V
R
H V
REF
SENSE
–
L R
REF
/
SENSE
L
•
N Value
65 536
DAC7641
,
100
100
V
OUT
Sense
V
OUT
2200pF
2200pF
(2)
24
23
22
V
18
SS
Figure 15 shows a DAC7641 in a 4mA to 20mA current
output configuration. The output current can be determined
by Equation 3:
At full-scale, the output current is 16mA plus the 4mA for
the zero current. At zero scale the output current is the offset
current of 4mA (0.5V/125 ).
OPA2350
I
OUT
I
OUT
V
R
PROGRAMMED
125
SENSE
2 5
.
V
125
+0.50v
– .
0 5
80k
V
20k
•
N Value
65 536
+V
,
+2.5V
125
0 5
.
V
(3)