Not Recommended for New Designs

PCA9517

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SCPS157E – DECEMBER 2007 – REVISED JUNE 2014

4 Description (Continued)

The B-side drivers operate from 2.7 V to 5.5 V and behave like the drivers in the PCA9515A. The output low

level for this internal buffer is approximately 0.5 V, but the input voltage must be 70 mV or more below the output

low level when the output internally is driven low. The higher-voltage low signal is called a buffered low. When

the B-side I/O is driven low internally, the low is not recognized as a low by the input. This feature prevents a

lockup condition from occurring when the input low condition is released.

This type of design on the B side prevents it from being used in series with the PCA9515A and another

PCA9517 (B side). This is because these devices do not recognize buffered low signals as a valid low and do

not propagate it as a buffered low again.

The A-side drivers operate from 0.9 V to 5.5 V and drive more current. They do not require the buffered low

feature (or the static offset voltage). This means that a low signal on the B side translates to a nearly 0-V low on

the A side, which accommodates smaller voltage swings of lower-voltage logic. The output pulldown on the

systems where the low-voltage-side supply voltage is as low as 0.9 V.

The A side of two or more PCA9517s can be connected together to allow a star topography, with the A side on

the common bus. Also, the A side can be connected directly to any other buffer with static- or dynamic-offset

voltage. Multiple PCA9517s can be connected in series, A side to B side, with no buildup in offset voltage and

with only time-of-flight delays to consider.

select when the repeater is active. This can be used to isolate a badly behaved slave on power-up reset. It

state only when the global bus and repeater port are in an idle state, to prevent system failures.

pulldown driver is turned off and the external pullup resistor pulls the pin high. When the B side falls first and

enabled unless the B-side voltage goes below 0.4 V. If the B-side low voltage does not go below 0.5 V, the A-

depends on the system, but each side of the repeater must have a pullup resistor. The device is designed to

Under certain conditions, higher termination currents can be used.

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