PCA9533D/01,118 Ver la hoja de datos (PDF) - NXP Semiconductors.
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PCA9533D/01,118 Datasheet PDF : 24 Pages
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NXP Semiconductors
8. Application design-in information
PCA9533
4-bit I2C-bus LED dimmer
5V
10 kΩ
I2C-BUS/SMBus
MASTER
SDA
SCL
10 kΩ
VDD
SDA
SCL
LED0
LED1
LED2
LED3
PCA9533
VSS
Fig 14. Typical application
5V
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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.
VDD
3.3 V
5V
VDD
LEDn
LED
100 kΩ
VDD
LED
LEDn
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Fig 15. High value resistor in parallel with
the LED
002aac190
Fig 16. Device supplied by a lower voltage
PCA9533_3
Product data sheet
Rev. 03 — 27 April 2009
© NXP B.V. 2009. All rights reserved.
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