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FS450, FS451
PRELIMINARY PRODUCT DESCRIPTION
JUNE, 2000, VERSION 1.2
54
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©
© 1999, 2000 FOCUS ENHANCEMENTS, INC.
PRELIMINARY INFORM ATION
+5V
R1
2.9K
R2
1.3K
R3
1.2K
Q1
D1
Q2
To
I2C
To
FS450
Figure 12. SIO Translation Using Current Mirrors
D1 = 1N4148, Q1 = 2N3906, Q2 = 2N3904
For applications with more than one supply, combinations of the above two circuits can be used. However,
the simplest approach to this problem is to limit the loading on the SIO bus when possible. When this is
not possible, some of the SIO passive loads can be replaced with active ones. This will increase the SIO
access speed without increasing the SIO output low drive current.
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