Introduction This document summarizes the most common customer questions regarding the NXP TJA1445, TJA1446, TJA1465 and TJA1466 CAN transceivers. It is intended as a practical guide covering basic product selection, partial networking, wake-up behavior, low-power operation, and key implementation considerations. 1) What are the TJA1445, TJA1446, TJA1465 and TJA1466 devices? They are high-speed CAN transceivers that provide the physical interface between a CAN/CAN FD controller and the two-wire CAN bus. All four devices support partial networking via selective wake-up, enabling low-power ECU operation while still allowing wake-up by a valid bus event or local wake input. 2) What is the main difference between the 1445/1446 and 1465/1466 families? The TJA1445/TJA1446 are high-speed CAN FD transceivers, while the TJA1465/TJA1466 are CAN SIC transceivers with Signal Improvement Capability, which reduces ringing and enables reliable communication in more complex topologies and at higher CAN FD speeds. The TJA1465/TJA1466 can support CAN FD up to 8 Mbit/s, whereas the TJA1445/TJA1446 target up to 5 Mbit/s CAN FD. 3) What is the difference between TJA1445 and TJA1446? Both support CAN FD and partial networking, but the TJA1446 adds advanced system monitoring features such as a Q&A watchdog, RST_N, LIMPFSO_N, and accurate VIO undervoltage/overvoltage monitoring. The TJA1445 does not include these monitoring and safety interface features. 4) What is the difference between TJA1465 and TJA1466? Both devices support CAN SIC, partial networking, and CAN FD/XL passive behavior, but the TJA1466 additionally integrates the watchdog, VIO monitoring, RST_N, and LIMPFSO_N fail-safe/limp-home support. The TJA1465 is the simpler CAN SIC partial networking transceiver without these advanced monitoring functions. 5) What is Partial Networking (PN), and why is it useful? Partial Networking allows ECUs that are not needed to remain in low-power mode while selected ECUs remain active on the bus. A sleeping node can be woken by a local wake event or by a remote selective wake-up frame containing the ECU-specific CAN identifier. This reduces vehicle power consumption and is especially useful for modern vehicles and EVs. 6) What is selective wake-up? Selective wake-up is the PN feature in which the transceiver does not wake up on arbitrary CAN traffic, but only on a valid wake-up frame matching the configured identifier, and optionally also matching DLC and data mask conditions. This helps keep undesired ECUs asleep even while other CAN messages are present on the bus. 7) What is the difference between CAN wake-up pattern (WUP) and wake-up frame (WUF)? A Wake-Up Pattern (WUP) is a low-level CAN bus pattern used to activate biasing and trigger wake-up when selective wake-up is not active. A Wake-Up Frame (WUF) is a valid CAN frame checked by the PN filter and used for selective wake-up when PN is configured and enabled. 😎 Which device should I choose for 8 Mbit/s CAN FD or more demanding network topologies? For higher CAN FD speeds and more challenging topologies, the TJA1465/TJA1466 are the preferred options because they include Signal Improvement Capability, which significantly reduces signal ringing and enables reliable operation up to 8 Mbit/s CAN FD. 9) Which VIO voltages are supported? The TJA1445/TJA1465 support interfacing with 1.8 V, 3.3 V, and 5 V MCUs. The TJA1446/TJA1466 are offered as dedicated variants: A = 1.8 V, B = 3.3 V, and C = 5 V-oriented / higher-voltage VIO variants. The 1446/1466 variant must be chosen to match the target MCU I/O level. 10) What supply pins do these transceivers use? They use three main supply pins: VBAT, VCC, and VIO. VBAT is the main supply and must be present in all operating modes, VCC supplies the CAN transmitter and biasing, and VIO supplies the digital interface level adaptation to the MCU. 11) What operating modes are available? The devices support Normal, ListenOnly, Standby, and Sleep modes. In Normal, the node can transmit and receive. In ListenOnly, the receiver is active but the transmitter is disabled. Standby is the first-level low-power mode with INH active, and Sleep is the deeper low-power mode with INH inactive. 12) What is the purpose of ListenOnly mode? ListenOnly mode is intended for node diagnosis, failure containment, and pretended networking use cases. In this mode the device can receive CAN traffic but does not actively transmit onto the bus. In low-power ListenOnly configurations, the receiver can remain active while minimizing current consumption. 13) How is local wake-up performed? Local wake-up is performed through the WAKE pin, which can be configured to detect rising and/or falling edges. A local wake-up request is registered when the new WAKE level remains stable for at least the configured wake filter time. 14) What are typical WAKE pin application examples? Typical examples include a switch to ground, connection to an ignition signal, or using the INH output of another transceiver as the wake source. We also provide design guidance for ESD protection and resistor/capacitor selection in these WAKE circuits. 15) What is the INH pin used for? The INH output is used to control external regulators or high-side enable logic so that the MCU and related circuitry can be automatically powered down in low-power modes and re-enabled on wake-up. In Sleep mode, it allows the transceiver to keep wake-up capability while the rest of the ECU is powered down. 16) How is selective wake-up configured? Selective wake-up is configured via SPI by programming the PN ID registers, ID mask, frame control, and data rate/filter registers. If data-field-based wake-up is needed, the DLC and data mask registers are also configured. The configuration becomes active after setting CPNC = 1 and PNCOK = 1. 17) What happens if I change a PN register after configuration? When the content of any PN-related register is changed, PNCOK is automatically cleared, and it must be set again to load and activate the updated PN configuration. 18) Can the device wake on identifier only, or also on data? Both are possible. The devices support identifier-only filtering when PNDM = 0, and identifier + DLC + data mask filtering when PNDM = 1. With data mask filtering, the wake-up decision also depends on the configured DLC and data mask bits. 19) Can Remote frames be used for selective wake-up? If PNDM = 1 and the selective wake-up checks the data field, Remote frames are not supported because they do not carry data. If Remote frames need to be able to trigger wake-up, identifier-only filtering should be used instead PNDM = 0. 20) How many MCU pins are needed to interface these devices? For the TJA1445/TJA1465, typically six MCU pins are needed: four SPI pins plus TXD and RXD. For the TJA1446/TJA1466, typically seven MCU pins are needed because the RST_N pin should also be connected to the MCU. 21) Are the SPI pins shareable with other peripherals? Yes. SCK, SDI, and SDO may be shared with other devices, but the transceiver requires its own dedicated SCSN chip-select. Daisy-chain SPI connections are not supported. 22) What are the GPIO pins used for? On the TJA1445B/TJA1465B, three GPIOs are available, and on the TJA1446/TJA1466, two GPIOs are available. They can be configured for general-purpose I/O and various special functions, including additional TXD/RXD, status signaling, wake-up input behavior, and other remote I/O style uses. 23) Can one transceiver be connected to two CAN controllers? Yes. GPIO1/2 can be configured as RXD2/TXD2, allowing a second CAN controller in the MCU to connect to the same transceiver. 24) What is TXEN_N and how does it behave? On the TJA1445B/TJA1465B, TXEN_N is the transmitter enable/disable control. A HIGH level on TXEN_N disables the CAN transmitter. In low-power modes, special care is needed so that the pin does not unnecessarily increase quiescent current if VIO remains present. 25) What extra features do TJA1446/TJA1466 provide for safety and system monitoring? The TJA1446/TJA1466 provide a Q&A watchdog, RST_N, LIMPFSO_N, and VIO undervoltage/overvoltage monitoring. They can supervise the MCU, detect fault conditions, trigger system reset, and support limp-home or fail-safe strategies in the ECU. 26) What is LIMPFSO_N used for? LIMPFSO_N can be configured either as a limp-home output or as a fail-safe output, depending on the system safety concept. In a limp-home application, it can activate backup hardware in case of failure. In a fail-safe application, it can keep safety-relevant hardware disabled until correct system operation is confirmed. 27) What is RST_N used for on TJA1446/TJA1466? RST_N is a bidirectional active-low reset pin used both to reset the MCU in response to transceiver-detected failures and to allow the transceiver to detect reset-related fault conditions from the system side. It should be connected to the MCU reset input. 28) What ESD robustness is specified on CANH and CANL? The quick reference data in the datasheets specifies ±8 kV IEC 61000-4-2 ESD handling capability on CANH and CANL. External protection components can still be considered if required by the application environment. 29) Is there any timing requirement for the first SPI access after power-up or wake-up? Yes. For the TJA1445/TJA1465 family, the first SPI interaction should occur within the MCU reaction timeout after power-up or wake-up from Sleep; otherwise the device may automatically enter Sleep mode with wake-up sources enabled. This mechanism helps limit battery drain if the MCU fails to initialize correctly. 30) Are there any common pitfalls when entering Sleep mode? Yes. Before entering Sleep, the required wake-up sources must be enabled and pending wake-up interrupts should be cleared. The transceiver will not enter Sleep unless at least one main wake-up source is enabled and all wake-up interrupts are cleared. 31) Can these devices support in-system MCU flashing through the CAN bus? Yes. The datasheets describe Start-to-Normal (SNM) behavior, which allows the device to enter Normal mode directly after boot if the CAN bus is held dominant before the internal check completes. This can support generic bootloader or end-of-line flashing use cases. 32) Are these devices safety-oriented parts? Yes. All four families were developed in compliance with ISO 26262 and achieve ASIL B. The TJA1446/TJA1466 go further with advanced monitoring and fail-safe-oriented interfacing. 33) Which packages are available? The TJA1445A/TJA1465A are available in SO14 and HVSON14, while the B variants are available in DHVQFN18. The TJA1446/TJA1466 are available in DHVQFN18. 34) Where can I find example initialization and SPI command guidance? For practical implementation guidance, we provide AN14388 for TJA1445/TJA1465 and AN14452 for TJA1446/TJA1466. These application notes include SPI usage guidance, initialization considerations, PN setup recommendations, WAKE pin examples, GPIO usage examples, and low-power mode handling. 35) In one sentence, when should I choose each family? Choose TJA1445 for CAN FD + PN, TJA1446 for CAN FD + PN + advanced system monitoring, TJA1465 for CAN SIC + PN + higher-speed or more demanding networks, and TJA1466 when you need CAN SIC plus advanced monitoring and safety-oriented system supervision.