ZHCS616E March 2012 – February 2017 TCA9554
PRODUCTION DATA.
- 1 特性
- 2 應(yīng)用
- 3 說明
- 4 修訂歷史記錄
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Parameter Measurement Information
- 8 Detailed Description
- 9 Application and Implementation
- 10Power Supply Recommendations
- 11Layout
- 12器件和文檔支持
- 13機(jī)械、封裝和可訂購信息
封裝選項(xiàng)
機(jī)械數(shù)據(jù) (封裝 | 引腳)
散熱焊盤機(jī)械數(shù)據(jù) (封裝 | 引腳)
- DW|16
訂購信息
9.2.1.2 Minimizing ICC when I/Os Control LEDs
When the I/Os are used to control LEDs, normally they are connected to VCC through a resistor as shown in Figure 26. For a P-port configured as an input, ICC increases as VI becomes lower than VCC. The LED is a diode, with threshold voltage VT, and when a P-port is configured as an input the LED is off but VI is a VT drop below VCC.
For battery-powered applications, it is essential that the voltage of P-ports controlling LEDs is greater than or equal to VCC when the P-ports are configured as input to minimize current consumption. Figure 27 shows a high-value resistor in parallel with the LED. Figure 28 shows VCC less than the LED supply voltage by at least VT. Both of these methods maintain the I/O VI at or above VCC and prevents additional supply current consumption when the P-port is configured as an input and the LED is off.
The TCA9554 has an integrated 100-kΩ pull-up resistor, so there is no need for an external pull-up.
Figure 27. High-Value Resistor in Parallel With LED
Figure 28. Device Supplied by a Lower Voltage