PCA9532 datasheet(13/29 Pages) NXP

13 / 29 page

PCA9532_4

Product data sheet

Rev. 04 — 17 March 2009

13 of 29

NXP Semiconductors

PCA9532

16-bit I2C-bus LED dimmer

Application design-in information

8.1 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 14. 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 and is speciﬁed as ∆IDD in Table 13 “Static characteristics”.

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 15 shows a high value resistor in parallel with the LED. Figure 16 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.

LED0 to LED12 are used as LED drivers.

LED13 to LED15 are used as regular GPIOs.

Fig 14. Typical application

PCA9532

LED0

LED1

SDA

SCL

RESET

5 V

I2C-BUS/SMBus

MASTER

002aae522

SDA

SCL

VDD

VSS

5 V

10 k

Ω

LED2

LED3

LED4

LED5

LED14

LED15

GPIOs

10 k

Ω

10 k

Ω

LED6

LED7

LED8

LED9

LED10

LED11

LED12

LED13

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