PCA9538 查看數據表（PDF） - Philips Electronics

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PCA9538

8-bit I2C and SMBus low power I/O port with interrupt and reset

Philips Electronics 

Philips Semiconductors

8-bit I2C and SMBus low power I/O port

with interrupt and reset

Product data sheet

PCA9538

TYPICAL APPLICATION

VDD

(5 V)

VDD

10 kΩ

SCL

MASTER

CONTROLLER

SDA

INT

IRESET

GND

10 kΩ 10 kΩ 10 kΩ

VDD

SCL

SDA

INT

IRESET

2 kΩ

I/O0

I/O1

I/O2

I/O3

I/O4

PCA9538

I/O5

I/O6

A1

I/O7

A0

100 kΩ

(×3)

SUBSYSTEM 1

(e.g. temp sensor)

INT

RESET

SUBSYSTEM 2

(e.g. counter)

A

ENABLE

B

Controlled Switch

(e.g. CBT device)

VSS

ALARM

NOTE: Device address configured as 1110000 for this example

I/O0, I/O2, I/O3, configured as outputs

I/O1, I/O4, I/O5, configured as inputs

I/O06, I/O7, are not used and need 100 kΩ pull-up resistors to protect them from floating.

SUBSYSTEM 3

(e.g. alarm

system)

VDD

SW02180

Figure 10. Typical application

Minimizing IDD when the I/O is 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 10. Since the LED acts as a

diode, when the LED is off the I/O VIN is about 1.2 V less than VDD. The supply current , IDD, increases as VIN becomes lower than VDD and is

specified as ∆IDD in the DC characteristics table.

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 11 shows a high value resistor in parallel with the LED. Figure 12 shows VDD less than the LED supply

voltage by at least 1.2 V. Both of these methods maintain the I/O VIN at or above VDD and prevents additional supply current consumption when

the LED is off.

VDD

3.3 V

5V

VDD

LEDx

LED

100 kΩ

SW02086

Figure 11. High value resistor in parallel with the LED

2004 Oct 05

8

VDD

LEDx

LED

SW02087

Figure 12. Device supplied by a lower voltage

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