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PCA9515

I2C-bus repeater

Philips Electronics 

Philips Semiconductors

I2C-bus repeater

VCC

SDA0

PCA9515

Product data sheet

PCA9515

SDA1

SCL0

SCL1

PULL-UP

RESISTOR

EN

GND

SU01323

Figure 2. PCA9515 block diagram

The output pull-down of each internal buffer is set for approximately

0.5 V, while the input threshold of each internal buffer is set about

0.07 V lower, when the output is internally driven LOW. This

prevents a lock-up condition from occurring.

FUNCTIONAL DESCRIPTION

The PCA9515 BiCMOS integrated circuit contains two identical

buffer circuits which enable I2C and similar bus systems to be

extended without degradation of system performance.

The PCA9515 BiCMOS integrated circuit contains two bi-directional,

open drain buffers specifically designed to support the standard

low-level-contention arbitration of the I2C-bus. Except during

arbitration or clock stretching, the PCA9515 acts like a pair of

non-inverting, open drain buffers, one for SDA and one for SCL.

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 operation because

disabling during a bus operation will hang the bus and enabling part

way through a bus cycle could confuse the I2C 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.

I2C Systems

As with the standard I2C 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 devices in addition to SMBus

devices. Standard mode I2C devices only specify 3 mA output drive,

this limits the termination current to 3 mA in a generic I2C 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 PCA9515/PCA9516 in a

system or using the PCA9515/16 in conjunction with the P82B96.

2004 Jun 24

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