9535 datasheet(10/19 Pages) PHILIPS

10 / 19 page

Philips Semiconductors

Product data

PCA9535

16-bit I2C and SMBus, low power I/O port with interrupt

2003 Jun 27

TYPICAL APPLICATION

SW02094

I/O0.0

I/O0.1

I/O0.2

I/O0.3

I/O0.4

I/O0.5

VDD

SCL

SDA

INT

RESET

MASTER

CONTROLLER

GND

SCL

SDA

PCA9535

VSS

VDD

SUBSYSTEM 3

(e.g. alarm system)

SUBSYSTEM 2

(e.g. counter)

SUBSYSTEM 1

(e.g. temp sensor)

INT

VDD

ALARM

Controlled Switch

(e.g. CBT device)

ENABLE

1.6 k

Ω

1.6 k

Ω

1.1 k

Ω

2 k

Ω

NOTE: Device address configured as 0100100 for this example

I/O0.0, I/O0.1, I/O0.2, configured as outputs

I/O0.3, I/O0.4, I/O0.5, configured as inputs

I/O0.6, I/O0.7, and I/O1.0 to I/O1.7 configured as inputs

2 k

Ω

INT

I/O0.6

I/O0.7

I/O1.0

I/O1.1

I/O1.2

I/O1.3

I/O1.4

I/O1.5

I/O1.6

I/O1.7

10 DIGIT

NUMERIC

KEYPAD

Figure 11. 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 11. 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 12 shows a high value resistor in parallel with the LED. Figure 13 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

LEDx

LED

100 k

SW02086

Figure 12. High value resistor in parallel with the LED

VDD

3.3 V

LEDx

LED

SW02087

5 V

Figure 13. Device supplied by a lower voltage

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