PCA9537 Datasheet, PDF(8/17 Page) NXP Semiconductors – 4-bit I2C and SMBus low power I/O port with interrupt and reset

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PCA9537 Datasheet, PDF (8/17 Pages) NXP Semiconductors – 4-bit I2C and SMBus low power I/O port with interrupt and reset

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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 kâ¦

10 kâ¦ 10 kâ¦ 10 kâ¦

SCL

MASTER

CONTROLLER

SDA

INT

RESET

GND

2 kâ¦

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 kâ¦

SUBSYSTEM 1

(e.g. temp sensor)

INT

RESET

SUBSYSTEM 2

(e.g. counter)

ENABLE

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 âIDD 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

VDD

I/Ox

LED

100 kâ¦

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

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