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9515A

I2C-bus repeater

NXP Semiconductors. 

NXP Semiconductors

PCA9515A

I2C-bus repeater

6. Functional description

Refer to Figure 1 “Functional diagram of PCA9515A”.

The PCA9515A integrated circuit contains two identical buffer circuits which enable

I2C-bus and similar bus systems to be extended without degradation of system

performance.

The PCA9515A contains two bidirectional, open-drain buffers specifically designed to

support the standard LOW-level contention arbitration of the I2C-bus. Except during

arbitration or clock stretching, the PCA9515A acts like a pair of non-inverting, open-drain

buffers, one for SDA and one for SCL.

6.1 Enable

The EN pin is active HIGH with an internal pull-up and allows the user to select when the

repeater is active. This can be used to isolate a badly behaved slave on power-up until

after the system power-up reset. It should never change state during an I2C-bus operation

because disabling during a bus operation will hang the bus and enabling part way through

a bus cycle could confuse the I2C-bus parts being enabled.

The enable pin should only change state when the global bus and the repeater port are in

an idle state to prevent system failures.

6.2 I2C-bus systems

As with the standard I2C-bus system, pull-up resistors are required to provide the logic

HIGH levels on the buffered bus (standard open-collector configuration of the I2C-bus).

The size of these pull-up resistors depends on the system, but each side of the repeater

must have a pull-up resistor. This part designed to work with Standard-mode and

Fast-mode I2C-bus devices in addition to SMBus devices. Standard-mode I2C-bus

devices only specify 3 mA output drive; this limits the termination current to 3 mA in a

generic I2C-bus system where Standard-mode devices and multiple masters are possible.

Under certain conditions higher termination currents can be used.

Please see Application Note AN255, I2C/SMBus Repeaters, Hubs and Expanders for

additional information on sizing resistors and precautions when using more than one

PCA9515A/PCA9516A in a system or using the PCA9515A/PCA9516A in conjunction

with the P82B96.

PCA9515A

Product data sheet

All information provided in this document is subject to legal disclaimers.

Rev. 5 — 23 March 2012

© NXP B.V. 2012. All rights reserved.

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