PCA9537 查看數據表（PDF） - Philips Electronics

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PCA9537

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

Philips Electronics 

Philips Semiconductors

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

with interrupt and reset

Product data sheet

PCA9537

TYPICAL APPLICATION

VDD

(5 V)

VDD

10 kΩ

10 kΩ 10 kΩ 10 kΩ

SCL

MASTER

CONTROLLER

SDA

INT

RESET

GND

2 kΩ

VDD

SCL

I/O0

SDA

I/O1

INT

I/O2

RESET

I/O3

PCA9537

VSS

NOTE: Device address is 1001001 for this example

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

I/O1, configured as input

Figure 9. Typical application

100 kΩ

SUBSYSTEM 1

(e.g. temp sensor)

INT

RESET

SUBSYSTEM 2

(e.g. counter)

A

ENABLE

B

Controlled Switch

(e.g. CBT device)

SW02189

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 9. 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 10 shows a high value resistor in parallel with the LED. Figure 11 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

I/Ox

LED

100 kΩ

SW02326

Figure 10. High value resistor in parallel with the LED

VDD

I/Ox

LED

SW02327

Figure 11. Device supplied by a lower voltage

2004 Nov 29

8

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