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| PCA9533 Datasheet, PDF (9/18 Pages) NXP Semiconductors – 4-bit I2C LED dimmer | |||
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Philips Semiconductors
4-bit I2C LED dimmer
Product data sheet
PCA9533
APPLICATION DATA
5V
5V
SDA
SCL
10 kâ¦
10 kâ¦
SDA
SCL
VDD
LED0
LED1
LED2
LED3
I2C/SMBus MASTER
VSS
PCA9533
Figure 13. Typical application
SW02047
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 13. 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 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 VIN at or above VDD and prevents additional supply current consumption when
the LED is off.
VDD
3.3 V
5V
VDD
LEDx
LED
100 kâ¦
SW02086
Figure 14. High value resistor in parallel with the LED
VDD
LEDx
LED
SW02087
Figure 15. Device supplied by a lower voltage
2004 Oct 01
9
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