UJA1078ATW/3V3/WD,

Specialized Overview

The UJA1078ATW/3V3/WD,1 is a System Basis Chip (SBC) from NXP Semiconductors designed for automotive Electronic Control Units (ECUs). It integrates a high-speed CAN transceiver compliant with ISO 11898-2 and ISO 11898-5, two LIN transceivers supporting LIN 2.2A and SAE J2602, and an advanced independent watchdog. The device features a scalable 3.3 V main voltage regulator (V1) delivering up to 250 mA for microcontroller supply, extendable via external PNP transistor, and a separate 5 V regulator (V2) for the CAN transceiver. Communication with the host MCU is facilitated through a full-duplex 16-bit Serial Peripheral Interface (SPI). The component operates within a battery voltage range of 4.5 V to 28 V and is housed in a 32-lead HTSSOP package.

Specialized Feature Summary

• Integrates high-speed CAN and dual LIN interfaces with dedicated low-dropout regulators for improved EMC performance and stable bus operation.
• Features a programmable watchdog with Window and Timeout modes, utilizing an on-chip oscillator for system reliability monitoring.
• Provides comprehensive power management including Standby, Sleep, and Normal modes with wake-up detection via CAN, LIN, or local pins.
• Includes diagnostic capabilities such as undervoltage warnings, overtemperature shutdown, and a limp home output for fault handling.

Specialized Applications

• Automotive Electronic Control Units (ECUs)
• Power and sensor peripheral control networks
• Gateway modules requiring CAN/LIN sub-bus integration

Specialized Procurement Notes

Verify the specific ordering suffix against the manufacturer's current datasheet revision to confirm regulatory compliance status and pin compatibility. Ensure that the selected variant matches the required voltage regulator output and watchdog configuration for the target application design.

Specialized Selection Notes

Select this component when a single-package solution for CAN and LIN networking is required alongside robust power management. The 3.3 V regulator version is suitable for microcontrollers operating at this logic level. Consider the external PNP transistor option if higher current distribution or thermal dissipation across the PCB is necessary for the specific load requirements.

Specialized Part Context

This part belongs to the UJA1078A family of core System Basis Chips. Variants within this family differ primarily by the output voltage of the main regulator (3.3 V vs. 5 V) and the inclusion of the watchdog timer functionality indicated by the 'WD' suffix. All variants share the same HTSSOP32 package and core interface specifications.

Specialized Replacement Considerations

The integrated CAN transceiver is downward compatible with the TJA1042. Designers replacing discrete components should verify that the replacement maintains the required SPI register map and voltage regulator thresholds for the existing microcontroller interface.

Specialized FAQ

What is the function of the WDOFF pin?

The WDOFF pin is used to deactivate the watchdog timer. When driven HIGH, it disables the watchdog and results in a software reset.

How does the device handle overtemperature conditions?

If the chip temperature exceeds the activation threshold, the SBC enters Overtemp mode, switching off voltage regulators and driving the LIMP pin LOW. It returns to Standby mode once the temperature drops below the release threshold.

Can the main voltage regulator current be extended?

Yes, the 250 mA main voltage regulator can be extended with an external PNP transistor to increase current capability and improve heat distribution over the PCB.