BA8274 View Datasheet(PDF) - ROHM Semiconductor
Part Name
Description
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BA8274 Datasheet PDF : 9 Pages
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Audio ICs
2. Loading calculations for the expanded I2C bus.
EXISTING
VCC
R1
PROPOSED BUS EXPANSION
R2
R3
BA8274 / F
5V
SDA
I2C
BA8274/F
LDA
BA8274/F
SDA
I2C
3000pF
GND
0V
Fig.4
Effective capacitance
Near I2C devices
2 × I2C Devices
Strays
BA8274 Buffer
20pF
20pF
10pF
Total Cap. 50pF
I2C pull-up
R1 = 1µsec = 20kΩ
50pF
Effective capacitance
Buffered line
Wiring Cap. 3000pF
Total Cap. 3000pF
Buffered bus pull-up
R2 = 1µsec = 333kΩ
3000pF
As an addition to an existing system:
R1 = 20kΩ
R2 = R2 × 0.1R3 = 300Ω
R2 + 0.1R3
R3 not required since buffer always connected.
For a permanent system:
1
R2 =
1
0.1R1
+
1
0.1R2
+
1
0.1R3
= 262Ω
R1 and R3 not required since buffer always connected.
Effective capacitance
Remote I2C devices
1 × I2C Devices
Strays
BA8274 Buffer
10pF
10pF
10pF
Total Cap. 30pF
I2C pull-up
R3 = 1µsec = 33kΩ
30pF
6/8
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