PCA9543A 데이터 시트보기 (PDF) - Philips Electronics
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PCA9543A Datasheet PDF : 24 Pages
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Philips Semiconductors
PCA9543A
2-channel I2C switch with interrupt logic and reset
7.4 Power-On Reset (POR)
When power is applied to VDD, an internal Power-on reset holds the PCA9543A in a reset
condition until VDD has reached VPOR. At this point, the reset condition is released and the
PCA9543A registers and I2C-bus state machine are initialized to their default states—all
zeroes—causing all the channels to be deselected. Thereafter, VDD must be lowered
below 0.2 V to reset the device.
7.5 Voltage translation
The pass gate transistors of the PCA9543A 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
Vo(sw)
(V)
4.0
3.0
2.0
002aaa964
(1)
(2)
(3)
1.0
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VDD (V)
(1) maximum
(2) typical
(3) minimum
Fig 6. Pass gate voltage versus supply voltage
Figure 6 shows the voltage characteristics of the pass gate transistors (note that the graph
was generated using the data specified in Section 11 “Static characteristics” of this data
sheet). In order for the PCA9543A to act as a voltage translator, the Vo(sw) 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 Vo(sw) should be
equal to or below 2.7 V to effectively clamp the downstream bus voltages. Looking at
Figure 6, we see that Vo(sw)(max) will be at 2.7 V when the PCA9543A supply voltage is
3.5 V or lower, so the PCA9543A 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 13).
More Information can be found in Application Note AN262: PCA954X family of I2C/SMBus
multiplexers and switches.
9397 750 14316
Product data sheet
Rev. 03 — 21 March 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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