PCA9530DP datasheet(10/24 Pages) NXP

10 / 24 page

PCA9530_3

Product data sheet

Rev. 03 — 26 February 2009

10 of 24

NXP Semiconductors

PCA9530

2-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 13. 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 12 “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 14 shows a high value resistor in parallel with the LED. Figure 15 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 prevent additional supply current consumption when the LED is off.

Fig 13. Typical application

PCA9530

LED0

LED1

SDA

SCL

RESET

3.3 V

I2C-BUS/SMBus

MASTER

002aae501

SDA

SCL

VDD

VSS

5 V

10 k

Ω

10 k

Ω

10 k

Ω

Fig 14. High value resistor in parallel with

the LED

Fig 15. Device supplied by a lower voltage

002aac189

LED

VDD

LEDn

100 k

Ω

VDD

002aac190

LED

VDD

LEDn

3.3 V

5 V

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