18 INDUSTRIAL AND AUTOMOTIVE SYSTEMS https://www.ti.com/ Issue 3 2025 Power Electronics Europe www.power-mag.com Not All Grounds Are 0V Sadia Khan - Systems Engineer, Isolation Products at Texas Instruments Industrial and automotive systems are using mixed-voltage designs for power optimization, improved performance, and cost reduction. Integration of diverse power domains become a challenge due to unintended ground mismatch. This occurs when the ground reference voltage between domains deviates from the expected 0V reference, ranging from a few volts to tens of volts. Ground shifts can disrupt communication between systems. Addressing this concern is key to reliable system performance. How is Ground Mismatch Solved Today? There are multiple methods today used by designers to address ground mismatch in systems. First, proper PCB grounding techniques are used such as dedicated ground planes, star grounding technique, and separating analog and digital grounds. However, this requires careful layout planning and can consume additional board space. If ground shift occurs after the board is already designed, this requires a complete redesign, leading to increased development time. Discrete level shifting is another technique, using resistor dividers or transistor- based circuits to interface across grounds. However, this design is not well-suited for systems with large ground potential differences, suffers from poor signal integrity and timing characteristics, and requires significant board space. Lastly, and perhaps the most commonly used, are galvanic based isolators which are used to decouple subsystems with different ground potentials. Isolators are often associated with higher costs and can introduce additional signal delays. This can also complicate power supply design since isolated sections require separate power sources. TI’s Latest Voltage and Ground-Level Translator Texas Instrument’s TXG family introduces a new method of mitigating ground mismatch in your system with a translator that can level shift both voltage and ground to enable communication across different power domains. TXG804x, TXG802x, and TXG8010 handles ground mismatch up to ±80V, level shifting of I/O voltages from 1.71V to 5.5V, and has a push-pull output for interfaces such as SPI, UART, I2S, and GPIOs. These devices support very high data rates of >250Mbps and low latency with <5ns propagation delay and 0.35ns channel- channel skew. TXG8122 also handles ground mismatch up to ±80V, level shifting of I/O voltages between 3V to 5.5V (Side 1) to 2.25V to 5.5V (Side 2), and has an open-drain output for interfaces like I2C. Examples of Ground Shifting There are several uses cases where ground mismatch can be an issue and is summarized below under three types of ground shifting: DC shift, AC Ground Noise, and Intentional Ground Shift. DC Shift Ground mismatch can occur due to DC shifts in a system and is shown in Figure 1. DC Shifts can be found when current flowing through a ground path causes a voltage drop because of the wire’s parasitics. This creates a ground mismatch between two systems. This phenomenon is particularly common in systems with high current loads or long ground paths. Figure 2 gives an example of an Electrical Power Steering (EPS) System. In this system, two microcontrollers (MCUs) are used to maintain continued operation during a failure event. Both MCUs communicate with each other, but one serves as a redundant backup in case the primary MCU stops functioning. While both MCUs are typically referenced to a common ground, high current loads in the system can introduce ground shifts between the two domains. Traditionally, digital isolators are used to manage these Figure 1. DC Shift Figure 2. Electric Power Steering with TXG Secondary Primary (Redundant)
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