SLVA704 June 2015 INA209 , INA219 , INA220 , INA220-Q1 , INA223 , INA226 , INA226-Q1 , INA228 , INA228-Q1 , INA230 , INA231 , INA233 , INA234 , INA237 , INA237-Q1 , INA238 , INA238-Q1 , INA3221 , INA3221-Q1 , LM8323 , LM8325-1 , LM8327 , LM8328 , LM8330 , LM8333 , LM8335 , OPT3001 , OPT3004 , P82B715 , P82B96 , PCA6107 , PCA9306 , PCA9306-Q1 , PCA9515A , PCA9515B , PCA9518 , PCA9534 , PCA9534A , PCA9535 , PCA9536 , PCA9538 , PCA9539 , PCA9543A , PCA9544A , PCA9545A , PCA9546A , PCA9548A , PCA9554 , PCA9554A , PCA9555 , PCA9557 , PCF8574 , PCF8574A , PCF8575 , PCF8575C , TCA1116 , TCA4311A , TCA5405 , TCA6408A , TCA6416A , TCA6418E , TCA6424A , TCA6507 , TCA8418 , TCA8418E , TCA8424 , TCA9406 , TCA9509 , TCA9517 , TCA9517A , TCA9534 , TCA9534A , TCA9535 , TCA9538 , TCA9539 , TCA9539-Q1 , TCA9543A , TCA9544A , TCA9545A , TCA9546A , TCA9548A , TCA9554 , TCA9554A , TCA9555 , TCA9617A , TCA9617B , TCA9800 , TCA9801 , TCA9802 , TCA9803
1.1.2 Open-Drain Releasing Bus
When the slave or master wishes to transmit a logic high, it may only release the bus by turning off the pull-down FET. This leaves the bus floating, and the pull-up resistor will pull the voltage up to the voltage rail, which will be interpreted as a high. Figure 4 shows the flow of current through the pull-up resistor, which pulls the bus high.
Figure 4. Releasing the Bus With An Open-Drain Interface