To solve the EMI and noise problems in electric vehicles, TI launches voltage regulators with integrated capacitors and ultra-low noise LDOs

In recent years, the field of power electronics has again received attention as systems such as electric vehicles have become increasingly popular. Since many of the subsystems in electric vehicles that affect efficiency, cost, and weight are power electronics related, improved power solutions are necessary to ensure that electric vehicles remain high-performance and low-priced in the future.

At the annual Applied Power Electronics Conference (APEC), Texas Instruments (TI) will release several power solutions designed to address these issues in electric vehicles.

Trends in Electric Vehicle Power Sources

Texas Instruments believes that the two most pressing issues in electric vehicle power systems are how to achieve low noise performance and low EMI.

“In the ’60s, the only thing that was relevant to automotive RF was the car radio, and that was the only thing that could be interfered with,” Morroni, power management R&D manager at Kilby Labs, told All About Circuit. “In today’s electric vehicles, there are many more systems, and they are all very sensitive. We have to protect these systems from interfering with each other, and that’s complicated.”

Some of the electrical systems in electric vehicles. Image courtesy of the U.S. Department of Energy

Overcoming the challenge of interference becomes important. First, electric vehicles require extremely high power systems and kilometers of cables, which generate a lot of EMI. At the same time, developers are introducing more and more sensitive analog electronic systems into vehicles to enable ADAS and autonomous driving functions. These two factors conflict with each other, and the question becomes, how do we design high-power electric vehicles to minimize EMI?

“ADAS systems tend to be very sensitive,” said Alex Chin, vice president of linear power at TI. “For example, CMOS image sensors around the vehicle are very susceptible to noise, and in addition to EMI, they also require power supplies with low noise levels.”

Therefore, the challenge is not just to eliminate EMI. Generally speaking, designers must also ensure low noise levels on the power rails for sensitive analog signals.

Low EMI Buck Converter

To meet the challenges of low EMI systems, Texas Instruments today announced two new step-down converter solutions.

The two products, LMQ66430 and LMQ66430-Q1, are 36V-3A power converters designed to mitigate EMI and noise in industrial and automotive applications. Notably, the converters are able to help reduce system EMI by integrating two input bypass capacitors and a startup capacitor on the package.

By integrating passive components, the high di/dt current loops that are typically present in such switching applications are reduced. In addition, the loop inductance is reduced, which can also support timing-critical switching elements such as GaN transistors.

The LMQ66430 integrates passive components into the package. Image courtesy of TI

“Integrating these passive components in the LMQ66430 allows us to control the loop inductance to reduce EMI,” explains Morroni. “Also, in the case of high-speed GaN switches, this allows us to drive the switch faster for higher efficiency.”

In addition to this, the buck converter has a quiescent current (Iq) of 1.5µA, which means the system has less leakage current when turned off.

Low Noise LDO Linear Regulator

Another product TI announced at APEC is the TPS7A94, a new low-dropout (LDO) linear regulator designed to achieve very low-noise performance.

Designed for use in extremely noise-sensitive devices, the new LDOs offer ultra-low output noise of 0.46µVRMS, a figure TI claims is 46% better than competitors. Additionally, to help isolate downstream components from upstream noise, the TPS7A94’s PSRR (power supply ripple rejection) is 100 dB at 1 kHz and 60 dB at 1 MHz.

Typical application circuit of TPS7A94. Image provided by TI

Discussing the new LDO, Chin said, “With the TPS7A94, we are actually trimming the two main sources of noise on the power rail. First, we reduce the noise generated by the LDO to industry-leading levels. Second, we provide very good PSRR performance to clean up the noise coming from the upstream power supply.”