NXP Semiconductors

PCA9537

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

7 Application design-in information

PCA9537

IO0

IO1

SCL

SDA

VDD

(5 V)

CONTROLLER

SCL

SDA

INT

IO2

VDD

VDD

VSS

INT

10 kΩ

SUB-SYSTEM 1

(e.g., temp sensor)

IO3

INT

SUB-SYSTEM 2

(e.g., counter)

RESET

controlled

switch

(e.g., CBT device)

A

B

enable

VSS

aaa-043259

10 kΩ

10 kΩ

2 kΩ

100 kΩ

RESET

RESET

10 kΩ

Device address is 1001 001x for this example.

IO0, IO2, IO3 configured as outputs.

IO1 configured as input.

Figure 9. Typical application

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.

002aac660

LED

VDD

IOn

100 kΩ

VDD

Figure 10. High value resistor in parallel

with the LED

002aac661

LED

VDD

IOn

3.3 V

5 V

Figure 11. Device supplied by a lower

voltage

PCA9537

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

© NXP B.V. 2021. All rights reserved.

Product data sheet

Rev. 7 — 8 September 2021

COMPANY PUBLIC

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