PCA9517A

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3

PIN ASSIGNMENT

Figure 2. SOIC8 / Micro8

PCA9517A

PIN DESCRIPTIONS

Symbol

Pin

Description

1

A−Side Supply Voltage (0.9 V to 5.5 V)

SCLA

2

Open−Drain I/O, Serial Clock A−Side Bus

SDAA

3

Open−Drain I/O, Serial Data A−Side Bus

GND

4

Ground

EN

5

Active−HIGH Repeater Enable

SDAB

6

Open−Drain I/O, Serial Data B−Side Bus

SCLB

7

Open−Drain I/O, Serial Clock B−Side Bus

8

B−Side Supply Voltage (2.7 V to 5.5 V)

FUNCTIONAL DESCRIPTION

Please refer to Figure 1 “Block Diagram of PCA9517A”.

system performance. The PCA9517A contains two

bidirectional open−drain buffers specifically designed to

support up−translation/down−translation between the low

SMBus. All inputs and I/Os are overvoltage tolerant to 5.5 V

= 0 V). The PCA9517A includes a power−up circuit that

be applied in any sequence at power−up.

After power−up and with the enable (EN) HIGH, a LOW

port B driver (either SDA or SCL) on and drives port B down

B pull−down driver is turned off and the external pull−up

resistor pulls the pin HIGH. When port B falls first and goes

pulls down to 0 V. The port B pull−down is not enabled

unless the port B voltage goes below 0.4 V. If the port B low

voltage does not go below 0.5 V, the port A driver will turn

low voltage goes below 0.4 V, the port B pull−down driver

is enabled and port B will only be able to rise to 0.5 V until

rise being pulled up by the external pull−up resistor. The

the port A input comparators and for the power good detect

circuit. The PCA9517A logic and all I/Os are powered by

Enable Pin (EN)

The EN pin is active HIGH with an internal pull−up to

active. This can be used to isolate a badly behaved slave on

power−up until after the system power−up reset. It should

disabling during a bus operation will hang the bus and

enabling part way through a bus cycle could confuse the

The EN pin should only change state when the global bus

and the repeater port are in an idle state to prevent system

failures.

required to provide the logic HIGH levels on the buffered

The size of these pull−up resistors depends on the system,

but each side of the repeater must have a pull−up resistor.