Biomedical Engineering Reference
In-Depth Information
For delay
1 To 5: Next delay
Next clocknum
Out princont, bit3
' update D/A data by deasserting 'CS
' without upsetting bit 3 of the Control port
' under this condition, clock and
' data states are of no relevance
dtoa
0
' dummy return variable
0
End Function
Current Sources
A current sources and an uncommit-
ted current mirror available on the universal sensor interface. Constant-current sources are
highly useful for the excitation of resistive sensors. Figure 5.6 shows various ways in which
the current source outputs and the current mirror can be connected to obtain the following:
A Burr-Brown REF200 IC is used to make two 100-
µ
• Two 100-
µ
A sources
• One 200-
µ
A source
• One 300-
µ
A source
• One 400-
µ
A source
10
0u
A
10
0
u
A
10
0
u
A
16
16
16
100uA Out
200uA Out
10
0
u
A
10
0
u
A
10
0
u
A
17
17
17
100uA Out
Current Mirror In
19
Current Mirror In
Current Mirror Out
Current Mirror In
Current Mirror Out
19
19
Current Mirror Out
+5V
20
20
20
Current Mirror Common
18
Current Mirror Common
Current Mirror Common
18
18
300uA Source
300uA Sink
Two 100uA Sources
200uA Source
10
0
uA
10
0
u
A
10
0
u
A
16
16
16
100uA Out
10
0
u
A
10
0
u
A
10
0
u
A
17
17
17
Current Mirror In
Current Mirror Out
19
Current Mirror In
Current Mirror Out
19
Current Mirror In
Current Mirror Out
19
20
20
20
+5V
100uA Sink
200uA Sink
Current Mirror Common
Current Mirror Common
Current Mirror Common
18
18
18
400uA Out
100uA Source and
100uA Sink
400uA Source
200uA Sink
Figure 5.6
The current sources and current mirror can be wired to obtain various configurations within the range 100 to 400 µA. (From
Prutchi [1999]. Reprinted with permission from
Popular Electronics
, June 1999 © Gernsback Publications Inc.)
Search WWH ::
Custom Search