Introduction

Recently, in the automobile industry, due to the evolution of car technology and changes in the environment, such as EV (electric vehicle), ADAS (advanced driver assistance system), AD (autonomous driving), and integration of ECU in response to security, traditional vehicle structures are being changed. We are entering a period of major change.

Along with this major transformation, the number of semiconductors installed in a single vehicle is increasing year by year, and as the processing power of MCU/SoC increases, there is a shift to higher power. Under these circumstances, if you are reading this article, do you have these concerns when designing an in-vehicle ECU?

- When using a power supply that supports large currents, heat generation becomes a problem, making it difficult to provide cooling support and heat dissipation mechanisms.
・Although we spent time developing a cooling and heat dissipation mechanism, the board size including peripheral components ended up increasing.
- With the increase in current, the amount of design and evaluation man-hours required to deal with noise has become enormous.
・Noise filter parts are being added more and more for noise countermeasures.

Analog Devices' secondary power supplies solve many of these problems. This time, we will introduce a secondary power supply equipped with a silent switcher function that makes it easy to reduce heat generation, large size, and low EMI due to the increased power of MCUs/SoCs, which are major design issues for automotive ECUs. .
*Silent switcher is a low EMI switching regulator provided by Analog Devices.

Please see the article below for details.
Cleared CISPR25 Class5 requirements! Switching regulator that facilitates noise design of automotive ECUs

What is a secondary power supply?

​Secondary power supply generally refers to the power supply from the second stage onwards, counting from the vehicle battery. A power supply that uses the step-down voltage from another regulator as input, rather than a regulator that inputs directly from the vehicle battery, is called a secondary power supply. Analog Devices' secondary power supplies offer a wide range of low voltage input / high output current products.

This time, we will introduce the benefits of using Analog Devices' secondary power supply, using the representative product "LTC3311S" as an example.

High conversion efficiency to solve heat generation issues

In the case of switching regulators, most of the heat generated by power supply ICs is due to the conversion efficiency of the power supply itself.

Therefore, it can be said that selecting a power supply IC with good conversion efficiency is the most important factor in overcoming the problem of heat generation.

ADI's secondary power supplies have a high conversion efficiency of over 92%, enabling conversion while reducing heat generation in cases where high power is required.

Two features that meet strict size requirements

Compact package with few peripheral components

As the entire car becomes more electrically equipped, demands on the size of in-vehicle ECUs are becoming stronger year by year, and at the same time, the issue of board size has become a major design point.

ADI's secondary power supply allows for a simple design with very few peripheral components while reducing package size.

The LTC3311S is a product that can output up to 12.5A of current while remaining compact in size with a 3mm x 3mm LQFN.

Industry-leading high-speed switching frequency

The LTC3311S can also be driven with industry-leading switching frequencies up to 10Mhz.

By increasing the switching frequency, it is possible to select parts with smaller capacitance and size for the Vout capacitor and inductor, which not only creates cost benefits by reducing the unit cost of peripheral parts and the number of parts, but also reduces design man-hours. Masu.

If you actually look at the LTC3311S demo board, you can see that the size, including the peripheral components, can be reduced to 1 cm square.

The factory setting of the LTC3311S demo board shown below has a switching frequency of 2 MHz, but by changing the frequency to 10 MHz, the capacitance of the inductor and Vout capacitor can be further reduced, and the overall size can be reduced to less than 1 cm square. can.

LTC3311S demo board top view

Analog Devices High Current Secondary Power Lineup

ADI's secondary power supplies have a line-up capable of high-current output that meets the high-current needs of ECUs.

It also has a Multiphase Operation function to support systems with even higher currents, such as over 20A.

As shown below, if you use 4pcs of LTC3311S and connect to each PGOOD pin, MODE/SYNC pin and ITH pin, it is possible to output Iout 50A.

Analog Devices has a wide lineup of high-current output secondary power supplies, and new devices are being released one after another as the company's main products. At Macnica, we can propose devices that match the customer's required specifications, so please feel free to contact us.

Inquiry

Regarding this product, our technical specialists can also propose devices that match the required specifications, so please feel free to contact us.