PCA9543 데이터 시트보기 (PDF) - Philips Electronics
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PCA9543 Datasheet PDF : 15 Pages
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Philips Semiconductors
2-channel I2C switch with interrupt logic and reset
Product data sheet
PCA9543
VOLTAGE TRANSLATION
The pass gate transistors of the PCA9543 are constructed such that
the VDD voltage can be used to limit the maximum voltage that will
be passed from one I2C-bus to another.
5.0
4.5
4.0
3.5
Vpass
3.0
2.5
2.0
1.5
1.0
2.0
Vpass vs. VDD
MAXIMUM
TYPICAL
2.5
3.0
3.5
4.0
VDD
MINIMUM
4.5
5.0
5.5
SW00820
Figure 5 shows the voltage characteristics of the pass gate
transistors (note that the graph was generated using the data
specified in the DC Characteristics section of this datasheet). In
order for the PCA9543 to act as a voltage translator, the Vpass
voltage should be equal to, or lower than the lowest bus voltage. For
example, if the main bus was running at 5 V, and the downstream
buses were 3.3 V and 2.7 V, then Vpass should be equal to or below
2.7 V to effectively clamp the downstream bus voltages. Looking at
Figure 5, we see that Vpass (max.) will be at 2.7 V when the
PCA9543 supply voltage is 3.5 V or lower so the PCA9543 supply
voltage could be set to 3.3 V. Pull-up resistors can then be used to
bring the bus voltages to their appropriate levels (see Figure 12).
More Information can be found in Application Note AN262 PCA954X
family of I2C/SMBus multiplexers and switches.
Figure 5. Vpass voltage
2004 Oct 01
5
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