PCA9554_9554A

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Product data sheet

Rev. 9 — 19 March 2013

6 of 35

NXP Semiconductors

PCA9554; PCA9554A

5.2 Pin description

[1]

be connected to supply ground for proper device operation. For enhanced thermal, electrical, and board

level performance, the exposed pad needs to be soldered to the board using a corresponding thermal pad

on the board and for proper heat conduction through the board, thermal vias need to be incorporated in the

PCB in the thermal pad region.

6.

Functional description

Refer to Figure 1 “Block diagram of PCA9554/PCA9554A”.

6.1 Registers

6.1.1 Command byte

The command byte is the first byte to follow the address byte during a write transmission.

It is used as a pointer to determine which of the following registers will be written or read.

Table 3.

Pin description

Symbol

Pin

Description

SO16, SSOP16,

TSSOP16

HVQFN16

SSOP20

A0

1

15

6

address input 0

A1

2

16

7

address input 1

A2

3

1

9

address input 2

IO0

4

2

10

input/output 0

IO1

5

3

11

input/output 1

IO2

6

4

12

input/output 2

IO3

7

5

14

input/output 3

86[1]

15

supply ground

IO4

9

7

16

input/output 4

IO5

10

8

17

input/output 5

IO6

11

9

19

input/output 6

IO7

12

10

20

input/output 7

INT

13

11

1

interrupt output (open-drain)

SCL

14

12

2

serial clock line

SDA

15

13

4

serial data line

16

14

5

supply voltage

n.c.

-

-

3, 8, 13, 18

not connected

Table 4.

Command byte

Command

Protocol

Function

0

read byte

Input Port register

1

read/write byte

Output Port register

2

read/write byte

Polarity Inversion register

3

read/write byte

Configuration register