These devices have internal pull ups on critical terminals to place the device into known states if the terminals float. See Table 9-2 for details on terminal bias conditions.
|TERMINAL||PULL UP or PULL DOWN||COMMENT|
|TXD||Pull up||Weakly biases TXD toward recessive to prevent bus blockage or TXD DTO triggering|
|nSTB||Pull down||Weakly biases nSTB terminal towards low power Standby mode to prevent excessive system power|
|EN||Pull down||Weakly biases EN terminal towards low power mode to prevent excessive system power|
The internal bias should not be relied on by design, especially in noisy environments but should be considered a fall back protection. Special care needs to be taken when the device is used with MCUs using open drain outputs. TXD is weakly internally pulled up. The TXD pull up strength and CAN bit timing require special consideration when this device is used with an open drain TXD output on the microprocessor CAN controller. An adequate external pull up resistor must be used to ensure that the TXD output of the microprocessor maintains adequate bit timing input to the CAN transceiver.