NXP Semiconductors PCA9555 Operational manual

1. General description

The PCA9555 is a 24-pin CMOS device that provides 16 bits of General Purpose parallel

Input/Output (GPIO) expansion for I2C-bus/SMBus applications and was developed to

enhance the NXP Semiconductors family of I2C-bus I/O expanders. The improvements

include higher drive capability, 5 V I/O tolerance, lower supply current, individual I/O

configuration, and smaller packaging. I/O expanders provide a simple solution when

additional I/O is needed for ACPI power switches, sensors, push buttons, LEDs, fans, etc.

The PCA9555 consists of two 8-bit Configuration (Input or Output selection); Input, Output

and Polarity Inversion (active HIGH or active LOW operation) registers. The system

master can enable the I/Os as either inputs or outputs by writing to the I/O configuration

bits. The data for each Input or Output is kept in the corresponding Input or Output

address compatible with the PCF8575, software changes are required due to the

enhancements, and are discussed in Application Note AN469.

The PCA9555 open-drain interrupt output is activated when any input state differs from its

corresponding input port register state and is used to indicate to the system master that

an input state has changed. The power-on reset sets the registers to their default values

and initializes the device state machine.

Three hardware pins (A0, A1, A2) vary the fixed I2C-bus address and allow up to eight

devices to share the same I2C-bus/SMBus. The fixed I2C-bus address of the PCA9555 is

the same as the PCA9554, allowing up to eight of these devices in any combination to

share the same I2C-bus/SMBus.

2. Features and benefits

Operating power supply voltage range of 2.3 V to 5.5 V

5 V tolerant I/Os

Polarity Inversion register

Active LOW interrupt output

Low standby current

Noise filter on SCL/SDA inputs

No glitch on power-up

Internal power-on reset

16 I/O pins which default to 16 inputs

0 Hz to 400 kHz clock frequency

ESD protection exceeds 2000 V HBM per JESD22-A114, 200 V MM per

JESD22-A115, and 1000 V CDM per JESD22-C101

PCA9555

16-bit I2C-bus and SMBus I/O port with interrupt

Rev. 10 — 8 November 2017 Product data sheet

Product data sheet Rev. 10 — 8 November 2017 2 of 34

NXP Semiconductors PCA9555

16-bit I2C-bus and SMBus I/O port with interrupt

Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA

Five packages offered: SO24, SSOP24, TSSOP24, HVQFN24 and HWQFN24

3. Ordering information

3.1 Ordering options

Table 1. Ordering information

Type number Topside mark Package

Name Description Version

PCA9555D PCA9555D SO24 plastic small outline package; 24 leads;

body width 7.5 mm SOT137-1

PCA9555DB PCA9555 SSOP24 plastic shrink small outline package; 24 leads;

bodywidth 5.3 mm SOT340-1

PCA9555PW PCA9555 TSSOP24 plastic thin shrink small outline package; 24 leads;

body width 4.4 mm SOT355-1

PCA9555BS 9555 HVQFN24 plastic thermal enhanced very thin quad flat package;

no leads; 24 terminals; body 4 40.85 mm SOT616-1

PCA9555HF P55H HWQFN24 plastic thermal enhanced very very thin quad flat

package; no leads; 24 terminals; body 4 40.75 mm SOT994-1

Table 2. Ordering options

Type number Orderable

part number Package Packing method Minimum

order

quantity

Temperature

PCA9555D PCA9555D,112 SO24 STANDARD MARKING * IC'S

TUBE - DSC BULK PACK 1200 Tamb =40 C to +85 C

PCA9555D,118 SO24 REEL 13" Q1/T1 *STANDARD

MARK SMD 1000

PCA9555DB PCA9555DB,112 SSOP24 STANDARD MARKING * IC'S

TUBE - DSC BULK PACK 826 Tamb =40 C to +85 C

PCA9555DB,118 SSOP24 REEL 13" Q1/T1 *STANDARD

MARK SMD 1000

PCA9555PW PCA9555PW,112 TSSOP24 STANDARD MARKING * IC'S

TUBE - DSC BULK PACK 1575 Tamb =40 C to +85 C

PCA9555PW,118 TSSOP24 REEL 13" Q1/T1 *STANDARD

MARK SMD 2500

PCA9555BS PCA9555BS,118 HVQFN24 REEL 13" Q1/T1 *STANDARD

MARK SMD 6000 Tamb =40 C to +85 C

PCA9555BSHP HVQFN24 REEL 13" Q2/T3 *STANDARD

MARK SMD 6000

PCA9555HF PCA9555HF,118 HWQFN24 REEL 13" Q1/T1 *STANDARD

MARK SMD 6000 Tamb =40 C to +85 C

Product data sheet Rev. 10 — 8 November 2017 3 of 34

NXP Semiconductors PCA9555

16-bit I2C-bus and SMBus I/O port with interrupt

4. Block diagram

5. Pinning information

5.1 Pinning

Remark: All I/Os are set to inputs at reset.

Fig 1. Block diagram of PCA9555

PCA9555

POWER-ON

RESET

002aac702

I2C-BUS/SMBus

CONTROL

INPUT

FILTER

SCL

SDA

VDD

INPUT/

OUTPUT

PORTS

IO0_0

VSS

8-bit

write pulse

read pulse

IO0_2

IO0_1

IO0_3

IO0_4

IO0_5

IO0_6

IO0_7

INPUT/

OUTPUT

PORTS

IO1_0

8-bit

write pulse

read pulse

IO1_2

IO1_1

IO1_3

IO1_4

IO1_5

IO1_6

IO1_7

INT

LP filter

VDD

Fig 2. Pin configuration for SO24

INT V

A1 SDA

A2 SCL

IO0_0 A0

IO0_1 IO1_7

IO0_2 IO1_6

IO0_3 IO1_5

IO0_4 IO1_4

IO0_5 IO1_3

IO0_6 IO1_2

IO0_7 IO1_1

IO1_0

PCA9555D

002aac698

Product data sheet Rev. 10 — 8 November 2017 4 of 34

NXP Semiconductors PCA9555

16-bit I2C-bus and SMBus I/O port with interrupt

Fig 3. Pin configuration for SSOP24 Fig 4. Pin configuration for TSSOP24

Fig 5. Pin configuration for HVQFN24 Fig 6. Pin configuration for HWQFN24

INT

IO0_0

IO0_1

IO0_2

IO0_3

IO0_4

IO0_5

IO0_6

IO0_7

VSS

PCA9555DB

002aac699

23 VDD

SDA

SCL

IO1_7

IO1_6

IO1_5

IO1_4

IO1_3

IO1_2

IO1_1

IO1_0

VDD

SDA

SCL

IO1_7

IO1_6

IO1_5

IO1_4

IO1_3

IO1_2

IO1_1

IO1_0

INT

IO0_0

IO0_1

IO0_2

IO0_3

IO0_4

IO0_5

IO0_6

IO0_7

VSS

PCA9555PW

002aac700

002aac701

PCA9555BS

Transparent top view

IO1_3

IO0_4

IO0_5

IO1_4

IO0_3 IO1_5

IO0_2 IO1_6

IO0_1 IO1_7

IO0_0 A0

IO0_6

IO0_7

VSS

IO1_0

IO1_1

IO1_2

VDD

SDA

SCL

terminal 1

index area

613

514

4 15

3 16

2 17

118

INT

002aac881

Transparent top view

IO1_3

IO0_4

IO0_5

IO1_4

IO0_3 IO1_5

IO0_2 IO1_6

IO0_1 IO1_7

IO0_0 A0

IO0_6

IO0_7

VSS

IO1_0

IO1_1

IO1_2

INT

VDD

SDA

SCL

terminal 1

index area

613

514

4 15

3 16

2 17

118

PCA9555HF

Product data sheet Rev. 10 — 8 November 2017 5 of 34

NXP Semiconductors PCA9555

16-bit I2C-bus and SMBus I/O port with interrupt

5.2 Pin description

[1] HVQFN and HWQFN package die supply ground is connected to both the VSS pin and the exposed center

pad. The VSS pin must 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.

Table 3. Pin description

Symbol Pin Description

SO24, SSOP24,

TSSOP24 HVQFN24,

HWQFN24

INT 1 22 interrupt output (open-drain)

A1 2 23 address input 1

A2 3 24 address input 2

IO0_0 4 1 port 0 input/output

IO0_1 5 2

IO0_2 6 3

IO0_3 7 4

IO0_4 8 5

IO0_5 9 6

IO0_6 10 7

IO0_7 11 8

VSS 12 9[1] supply ground

IO1_0 13 10 port 1 input/output

IO1_1 14 11

IO1_2 15 12

IO1_3 16 13

IO1_4 17 14

IO1_5 18 15

IO1_6 19 16

IO1_7 20 17

A0 21 18 address input 0

SCL 22 19 serial clock line

SDA 23 20 serial data line

VDD 24 21 supply voltage

Product data sheet Rev. 10 — 8 November 2017 6 of 34

NXP Semiconductors PCA9555

16-bit I2C-bus and SMBus I/O port with interrupt

6. Functional description

Refer to Figure 1 “Block diagram of PCA9555”.

6.1 Device address

6.2 Registers

6.2.1 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.

Fig 7. PCA9555 device address

R/W

002aac219

0 1 0 0 A2 A1 A0

programmable

slave address

fixed

Table 4. Command byte

Command Register

0 Input port 0

1 Input port 1

2 Output port 0

3 Output port 1

4 Polarity Inversion port 0

5 Polarity Inversion port 1

6 Configuration port 0

7 Configuration port 1

Product data sheet Rev. 10 — 8 November 2017 7 of 34

NXP Semiconductors PCA9555

16-bit I2C-bus and SMBus I/O port with interrupt

6.2.2 Registers 0 and 1: Input port registers

This register is an input-only port. It reflects the incoming logic levels of the pins,

regardless of whether the pin is defined as an input or an output by Register 3. Writes to

this register have no effect.

The default value ‘X’ is determined by the externally applied logic level.

6.2.3 Registers 2 and 3: Output port registers

This register is an output-only port. It reflects the outgoing logic levels of the pins defined

as outputs by Registers 6 and 7. Bit values in this register have no effect on pins defined

as inputs. In turn, reads from this register reflect the value that is in the flip-flop controlling

the output selection, not the actual pin value.

6.2.4 Registers 4 and 5: Polarity Inversion registers

This register allows the user to invert the polarity of the Input port register data. If a bit in

this register is set (written with ‘1’), the Input port data polarity is inverted. If a bit in this

Table 5. Input port 0 Register

Bit 7 6 5 4 3 2 1 0

Symbol I0.7 I0.6 I0.5 I0.4 I0.3 I0.2 I0.1 I0.0

Default XXXXXXXX

Table 6. Input port 1 register

Bit 7 6 5 4 3 2 1 0

Symbol I1.7 I1.6 I1.5 I1.4 I1.3 I1.2 I1.1 I1.0

Default XXXXXXXX

Table 7. Output port 0 register

Bit 7 6 5 4 3 2 1 0

Symbol O0.7 O0.6 O0.5 O0.4 O0.3 O0.2 O0.1 O0.0

Default 11111111

Table 8. Output port 1 register

Bit 7 6 5 4 3 2 1 0

Symbol O1.7 O1.6 O1.5 O1.4 O1.3 O1.2 O1.1 O1.0

Default 11111111

Table 9. Polarity Inversion port 0 register

Bit 7 6 5 4 3 2 1 0

Symbol N0.7 N0.6 N0.5 N0.4 N0.3 N0.2 N0.1 N0.0

Default 00000000

Table 10. Polarity Inversion port 1 register

Bit 7 6 5 4 3 2 1 0

Symbol N1.7 N1.6 N1.5 N1.4 N1.3 N1.2 N1.1 N1.0

Default 00000000

Product data sheet Rev. 10 — 8 November 2017 8 of 34

NXP Semiconductors PCA9555

16-bit I2C-bus and SMBus I/O port with interrupt

6.2.5 Registers 6 and 7: Configuration registers

This register configures the directions of the I/O pins. If a bit in this register is set (written

with ‘1’), the corresponding port pin is enabled as an input with high-impedance output

driver. If a bit in this register is cleared (written with ‘0’), the corresponding port pin is

enabled as an output. Note that there is a high value resistor tied to VDD at each pin. At

reset, the device's ports are inputs with a pull-up to VDD.

6.3 Power-on reset

When power is applied to VDD, an internal power-on reset holds the PCA9555 in a reset

condition until VDD has reached VPOR. At that point, the reset condition is released and the

PCA9555 registers and SMBus state machine will initialize to their default states. The

power-on reset typically completes the reset and enables the part by the time the power

supply is above VPOR. However, when it is required to reset the part by lowering the power

supply, it is necessary to lower it below 0.2 V.

6.4 I/O port

When an I/O is configured as an input, FETs Q1 and Q2 are off, creating a

high-impedance input with a weak pull-up to VDD. The input voltage may be raised above

VDD to a maximum of 5.5 V.

If the I/O is configured as an output, then either Q1 or Q2 is on, depending on the state of

the Output Port register. Care should be exercised if an external voltage is applied to an

I/O configured as an output because of the low-impedance path that exists between the

pin and either VDD or VSS.

Table 11. Configuration port 0 register

Bit 7 6 5 4 3 2 1 0

Symbol C0.7 C0.6 C0.5 C0.4 C0.3 C0.2 C0.1 C0.0

Default 11111111

Table 12. Configuration port 1 register

Bit 7 6 5 4 3 2 1 0

Symbol C1.7 C1.6 C1.5 C1.4 C1.3 C1.2 C1.1 C1.0

Default 11111111

Product data sheet Rev. 10 — 8 November 2017 9 of 34

NXP Semiconductors PCA9555

16-bit I2C-bus and SMBus I/O port with interrupt

6.5 Bus transactions

6.5.1 Writing to the port registers

Data is transmitted to the PCA9555 by sending the device address and setting the least

significant bit to a logic 0 (see Figure 7 “PCA9555 device address”). The command byte is

sent after the address and determines which register will receive the data following the

command byte.

The eight registers within the PCA9555 are configured to operate as four register pairs.

The four pairs are Input Ports, Output Ports, Polarity Inversion Ports, and Configuration

Ports. After sending data to one register, the next data byte will be sent to the other

Output Port 1 (register 3), then the next byte will be stored in Output Port 0 (register 2).

There is no limitation on the number of data bytes sent in one write transmission. In this

way, each 8-bit register may be updated independently of the other registers.

At power-on reset, all registers return to default values.

Fig 8. Simplified schematic of I/Os

I/O pin

output port

configuration

CK Q

data from

shift register

write

configuration

pulse

output port

write pulse

polarity inversion

data from

shift register

write polarity

pulse

input port

read pulse

input port

polarity

inversion

002aac703

data from

shift register

to INT

100 kΩ

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Product data sheet Rev. 10 — 8 November 2017 10 of 34

NXP Semiconductors PCA9555

16-bit I2C-bus and SMBus I/O port with interrupt

Fig 9. Write to Output port registers

1 0 0 A2 A1 A0 0 AS0

START condition R/W acknowledge

from slave

002aac220

SCL

SDA A

write to port

data out

from port 0

tv(Q)

987654321

command byte data to port 0

DATA 0

slave address

00000100

STOP

condition

0.00.7

acknowledge

from slave acknowledge

from slave

data to port 1

DATA 1 1.01.7 A

data out

from port 1

tv(Q)

DATA VALID

Fig 10. Write to Configuration registers

1 0 0 A2 A1 A0 0 AS0

START condition R/W acknowledge

from slave

002aac221

SCL

SDA A P

987654321

command byte data to register

DATA 0

slave address

00001100

STOP

condition

LSBMSB

acknowledge

from slave acknowledge

from slave

data to register

DATA 1

LSBMSB

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