9551 查看數據表（PDF） - NXP Semiconductors.
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9551 Datasheet PDF : 26 Pages
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NXP Semiconductors
PCA9551
8-bit I2C-bus LED driver with programmable blink rates
8. Application design-in information
5V
I2C-BUS/SMBus
MASTER
SDA
SCL
10 kΩ
10 kΩ
10 kΩ
VDD
PCA9551
SDA
LED0
SCL
LED1
LED2
RESET
LED3
LED4
LED5
LED6
A2
LED7
A1
A0
VSS
002aac510
LED0 to LED5 are used as LED drivers.
LED6 and LED7 are used as regular GPIOs.
Fig 14. Typical application
5V
GPIOs
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 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 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
PCA9551_8
Product data sheet
VDD
LEDn
LED
100 kΩ
VDD
LED
LEDn
002aac189
002aac190
Fig 15. High value resistor in parallel with Fig 16. Device supplied by a lower voltage
the LED
Rev. 08 — 31 July 2008
© NXP B.V. 2008. All rights reserved.
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