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PCA9548ABS

8-channel I2C switch with reset

Philips Electronics 

Philips Semiconductors

PCA9548A

8-channel I2C switch with reset

7.5 Voltage translation

The pass gate transistors of the PCA9548A 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 7. Pass gate voltage versus supply voltage

Figure 7 shows the voltage characteristics of the pass gate transistors (note that the

PCA9548A is only tested at the points specified in Section 11 “Static characteristics” of

this data sheet). In order for the PCA9548A 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 7, we see that Vo(sw)(max) will be at 2.7 V when the PCA9548A supply

voltage is 3.5 V or lower, so the PCA9548A 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 14).

More Information can be found in Application Note AN262: PCA954X family of I2C/SMBus

multiplexers and switches.

9397 750 13297

Product data sheet

Rev. 01 — 15 April 2005

© Koninklijke Philips Electronics N.V. 2005. All rights reserved.

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