Datasheet NCV7329 (ON Semiconductor) - 7

NCV7329 FUNCTIONAL DESCRIPTION Overall Functional Description
In case the junction temperature increases above the LIN is a serial communication protocol that efficiently thermal shutdown threshold (TJ(sd)), e.g. due to a short of the supports the control of mechatronic nodes in distributed LIN wiring to the battery, the transmitter is disabled and automotive applications. releases the LIN bus to recessive. Once the junction The NCV7329 contains the LIN transmitter, LIN receiver, temperature decreases back below the thermal shutdown power−on−reset (POR) circuits and thermal shutdown level, the transmission can be enabled again. However, to (TSD). The LIN transmitter is optimized for a maximum avoid thermal oscillations, first a High logical level on TxD specified transmission speed of 20 kbps. must be encountered before the transmitter is enabled. As required by SAE J2602, the transceiver must behave
Table 6. OPERATING MODES
safely below its operating range – it shall either continue to transmit correctly (according its specification) or remain
Pin EN Mode Pin RxD LIN bus
silent (transmit a recessive state regardless of the TxD x Unpowered Floating OFF; Floating signal). A battery monitoring circuit in NCV7329 Low Sleep Floating OFF; Floating deactivates the transmitter in the Normal mode if the VBB level drops below MONL_V Low Standby Low indicates OFF; 30 kW BB. Transmission is enabled wake−up again when VBB reaches MONH_VBB. The internal logic remains in the normal mode and the reception from the LIN High Normal LOW: dominant ON; 30 kW line is still possible even if the battery monitor disables the HIGH: reces- sive transmission. Although the specifications of the monitoring and power−on−reset levels are overlapping, it’s ensured by
Unpowered Mode
the implementation that the monitoring level never falls As long as VBB remains below its power−on−reset level, below the power−on−reset level. the chip is kept in a safe unpowered state. The LIN The Normal mode can be entered from either Standby or transmitter is inactive, the LIN pin is left floating and only Sleep mode when EN Pin is High for longer than tENABLE. a weak pull−down is connected on pin TxD. Pin RxD When the transition is made from Standby mode, TxD remains floating. pull−down is set to weak and RxD is put into a The unpowered state will be entered from any other state high−impedance immediately after EN becomes High when VBB falls below its power−on−reset level (before the expiration of tENABLE filtering time). This (PORL_VBB). When VBB rises above the power−on−reset excludes signal conflicts between the Standby mode pin high threshold (PORH_VBB), the NCV7329 switches to a settings and the signals required to control the chip in the Sleep mode. Normal mode after a local wake−up vs. High logical level on TxD required to send a recessive symbol to the LIN bus.
Normal Mode
In the Normal mode, the full functionality of the LIN
Sleep Mode
transceiver is available. The transceiver can transmit and Sleep mode provides extremely low current consumption. receive data via the LIN bus with speed up to 20 kbps. Data The LIN transceiver is inactive and the battery consumption according the state of TxD input are sent to the LIN bus is minimized. while pin RxD reflects the logical symbol received on the This mode is entered in one of the following ways: LIN bus − high−impedant for recessive and Low for • After the voltage level at VBB pin rises above its dominant. A 30 kW resistor in series with a power−on−reset level (PORH_VBB). In this case, RxD reverse−protection diode is internally connected between Pin remains high−impedant and the pull−down applied LIN and VBB pins. on pin TxD remains weak. The signal on pin TxD passes through a timer, which • After assigning Low logical level to pin EN for longer releases the bus in case the TxD remains low for longer than than t t DISABLE while NCV7329 is in the Normal mode. TxD_TIMEOUT. It prevents the LIN bus being permanently driven dominant and thus blocking all subsequent
Standby Mode
communication due to a failure of the application (e.g. Standby mode is entered from the Sleep mode when a software error). The transmission can continue once the remote wake−up event occurred. The Low level on RxD pin TxD returns to High logical level. indicates interrupt flag for the microcontroller.
www.onsemi.com 7