PCA9554C 查看數據表（PDF） - NXP Semiconductors.

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PCA9554C

Low-voltage 8-bit I2C-bus and SMBus low power I/O port with interrupt, weak pull-up

NXP Semiconductors. 

NXP Semiconductors

PCA9554B; PCA9554C

Low-voltage 8-bit I2C-bus/SMBus low power I/O port

8. Application design-in information

VDD

(3.3 V)

VDD

MASTER

CONTROLLER

SCL

SDA

INT

VSS

10 kΩ

10 kΩ

10 kΩ

VDD

2 kΩ

PCA9554B

SCL

P0

SDA

P1

INT

P2

P3

P4

P5

A2

A1

P6

A0

P7

VSS

100 kΩ

(× 3)(1)

SUB-SYSTEM 1

(e.g., temp sensor)

INT

SUB-SYSTEM 2

(e.g., counter)

RESET

A

enable

controlled

switch

(e.g., CBT device)

B

SUB-SYSTEM 3

(e.g., alarm system)

ALARM

Device address is 0100 000x for this example (PCA9554B).

P0, P2, P3 configured as outputs.

P1, P4, P5 configured as inputs.

(1) External resistors are not needed due to the internal weak pull-up resistors.

Fig 11. Typical application

VDD

002aah128

8.1 Minimizing IDD when the I/Os are used to control LEDs

When the I/Os are used to control LEDs, they are normally connected to VDD through a

resistor as shown in Figure 11. Since the LED acts as a diode, when the LED is off the

I/O VI is about 1.2 V less than VDD. The supply current, IDD, increases as VI becomes

lower than VDD.

Designs needing to minimize current consumption, such as battery power applications,

should consider maintaining the I/O pins greater than or equal to VDD when the LED is off.

Figure 12 and Figure 13 show typical solutions to minimizing current consumption.

Figure 12 shows a high value resistor in parallel with the LED. Figure 13 shows VDD less

than the LED supply voltage by at least 1.2 V. However, the PCA9554B/PCA9554C needs

no external resistors due to the integrated 100 k pull-up resistors.

PCA9554B_PCA9554C

Product data sheet

All information provided in this document is subject to legal disclaimers.

Rev. 1 — 19 September 2012

© NXP B.V. 2012. All rights reserved.

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