PCA9549 datasheet(7/24 Pages) PHILIPS

7 / 24 page

PCA9549_1

Product data sheet

Rev. 01 — 11 July 2006

7 of 24

Philips Semiconductors

PCA9549

Octal bus switch with individually I2C-bus controlled enables

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

PCA9549 is only tested at the points speciﬁed in Section 9 “Static characteristics”). In

order for the PCA9549 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)

(maximum) will be at 2.7 V when the PCA9549 supply voltage is 3.5 V or lower so the

PCA9549 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 16).

(1) maximum

(2) typical

(3) minimum

Fig 7.

Vo(sw) voltage versus VDD

VDD (V)

2.0

5.5

4.5

3.0

4.0

002aaa964

3.0

2.0

4.0

5.0

Vo(sw)

(V)

1.0

3.5

5.0

2.5

(1)

(2)

(3)

PCA9549 데이터시트(PDF) 7 Page - NXP Semiconductors