PCA9516AD datasheet(6/19 Pages) NXP

6 / 19 page

PCA9516A_3

Product data sheet

Rev. 03 — 23 April 2009

6 of 19

NXP Semiconductors

PCA9516A

5-channel I2C-bus hub

The PCA9516A is 5.5 V tolerant so it does not require any additional circuitry to translate

between the different bus voltages.

When one side of the PCA9516A is pulled LOW by a device on the I2C-bus, a CMOS

hysteresis type input detects the falling edge and causes an internal driver on the other

side to turn on, thus causing the other side to also go LOW. The side driven LOW by the

PCA9516A will typically be at VOL = 0.5 V.

In order to illustrate what would be seen in a typical application, refer to Figure 6 and

Figure 7. If the bus master in Figure 5 were to write to the slave through the PCA9516A,

we would see the waveform shown in Figure 6 on Bus 0. This looks like a normal I2C-bus

transmission until the falling edge of the 8th clock pulse. At that point, the master releases

the data line (SDA) while the slave pulls it LOW through the PCA9516A. Because the VOL

of the PCA9516A is typically around 0.5 V, a step in the SDA will be seen. After the master

has transmitted the 9th clock pulse, the slave releases the data line.

On the Bus 1 side of the PCA9516A, the clock and data lines would have a positive offset

from ground equal to the VOL of the PCA9516A. After the 8th clock pulse, the data line will

be pulled to the VOL of the slave device that is very close to ground in our example.

It is important to note that any arbitration or clock stretching events on Bus 1 require that

the VOL of the devices on Bus 1 be 70 mV below the VOL of the PCA9516A (see VOL−VILc

in Section 9 “Static characteristics”) to be recognized by the PCA9516A and then

transmitted to Bus 0.

Fig 5.

Typical application

002aae617

SCL1

SDA1

SLAVE 1

SDA

SCL

400 kHz

5 V

SCL2

SDA2

SLAVE 2

SDA

SCL

400 kHz

3.3 V

SCL3

SDA3

SLAVE 3

SDA

SCL

100 kHz

5 V

SCL4

SDA4

3.3 V or 5 V

PCA9516A

VCC

SCL0

SDA0

SCL

3.3 V

SDA

EN2

EN1

EN3

EN4

BUS

MASTER

400 kHz

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