PCA9537 View Datasheet(PDF) - NXP Semiconductors.

Part Name

Description

Manufacturer

PCA9537

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

NXP Semiconductors. 

NXP Semiconductors

PCA9537

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

7. Application design-in information

VDD

(5 V)

VDD

MASTER

CONTROLLER

SCL

SDA

INT

RESET

VSS

10 kΩ

10 kΩ

10 kΩ

10 kΩ

VDD

PCA9537

SCL

IO0

SDA

IO1

INT

IO2

RESET

IO3

VSS

Fig 9.

Device address is 1001 001x for this example.

IO0, IO2, IO3 configured as outputs.

IO1 configured as input.

Typical application

2 kΩ 100 kΩ

SUB-SYSTEM 1

(e.g., temp sensor)

INT

SUB-SYSTEM 2

(e.g., counter)

RESET

A

enable

controlled

switch

(e.g., CBT device)

B

002aae640

7.1 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 9. 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 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 VI

at or above VDD and prevents additional supply current consumption when the LED is off.

VDD

3.3 V

5V

VDD

IOn

LED

100 kΩ

VDD

LED

IOn

002aac660

Fig 10. High value resistor in parallel with

the LED

002aac661

Fig 11. Device supplied by a lower voltage

PCA9537_5

Product data sheet

Rev. 05 — 7 May 2009

© NXP B.V. 2009. All rights reserved.

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