TJA1021T/20/C
TJA1021T/20/C - LIN 2.1 Transceiver, 20kBd, 8-SO | NXP
The NXP TJA1021T/20/C is a single-wire LIN (Local Interconnect Network) bus transceiver that operates as the physical interface between a LIN protocol controller and the physical bus in in-vehicle sub-networks. The /20 variant supports baud rates from 1 kBd up to 20 kBd and is compliant with LIN 2.0, LIN 2.1, LIN 2.2, LIN 2.2A, SAE J2602 and ISO 17987-4:2016. It is housed in an 8-pin SO (SOIC-8) surface-mount package and is pin-to-pin compatible with the legacy TJA1020 and NXP MC33662(B) LIN transceivers.
What is a LIN transceiver? A LIN transceiver is a physical-layer (PHY) device that translates the low-voltage digital logic signals (TXD/RXD) generated by a microcontroller or LIN controller into the single-wire, dominant/recessive, slew-rate-controlled bus waveform defined by the LIN standard. It handles bus fault protection (short to battery, short to ground, load-dump), ESD protection, thermal shutdown, and wake-up detection via the bus line. The LIN protocol is widely used as a low-cost sub-bus for non-critical automotive body electronics (mirror controls, seat adjusters, door modules, roof consoles), where CAN would be over-spec.
Key features of the TJA1021T/20/C include an integrated slew-rate-controlled LIN bus driver that meets the LIN 2.1/SAE J2602 wave-shaping requirements with minimized electromagnetic emissions (EME), improved ESD robustness compared to the TJA1020, a -27 V to +40 V wide bus load-dump protection range, low-power sleep mode with remote wake-up via the LIN pin, and a dedicated TXD dominant time-out to prevent the bus from being permanently driven.
Architecturally, the TJA1021T/20/C uses a bipolar high-voltage process for the bus-side driver stage combined with low-voltage CMOS logic on the protocol-side (TXD, RXD, EN, WAKE). The integrated pull-up resistor on the bus line and the internal slope-control feedback loop produce the trapezoidal LIN waveform specified by SAE J2602, eliminating the need for an external diode or waveform-shaping RC network. Built-in fail-safe features include loss-of-bat handling, ground-shift tolerance, and under-voltage reset on VCC.
Typical applications include automotive body-control modules, LIN slaves for door/window/seat/steering-column control, HVAC flap motors, mirror adjusters, ambient lighting nodes, and rain/light sensors. Because the part is qualified to the AEC-Q100 automotive reliability standard, it is designed for the harsh electrical environment of a 12 V automotive battery rail, including jump-start and load-dump transients. It also suits industrial LIN sub-buses where the LIN standard provides a simple, robust single-wire alternative to CAN or RS-485.
When designing with this device, ensure the master resistor (typically 660 ohms pull-up to VSUP through a diode) and the bus capacitor (typically 220 pF to 1 nF) are correctly sized, and that the LIN node wake-up strategy (local wake via the WAKE pin vs remote wake via the bus) matches the application requirements.
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