“In recent years, automotive electronics have become increasingly important in automotive system design. You may also often hear about the increasing number of convenience features in cars, more advanced infotainment, driver assistance systems, and great strides in driverless cars. To drive innovation in automotive systems, the size of each new device must be optimized to meet increasingly stringent design requirements. But what does this mean for the power tree that powers various devices?
In recent years, automotive electronics have become increasingly important in automotive system design. You may also often hear about the increasing number of convenience features in cars, more advanced infotainment, driver assistance systems, and great strides in driverless cars. To drive innovation in automotive systems, the size of each new device must be optimized to meet increasingly stringent design requirements. But what does this mean for the power tree that powers various devices?
In the first and second part of this article, I will explore how innovation is changing the automotive electronics market and how TI is helping to solve a pervasive design problem in this area by integrating buck converters and LDOs.
Most Electronic Control Units (ECUs) require at least two regulating rails to efficiently power the various components of the system. Although two rails are required, the current requirements of the two rails are very different.
Take LED ceiling lights with haptic feedback, for example. The device’s power supply system requires a 5V rail to power both the LED driver and the haptic driver that controls the deflection mass motor (ERM). Both LEDs and haptic drivers are current-intensive devices with current requirements of approximately 2A. Using a buck converter is the best option for supplying this type of current because it enables efficient current conversion so that the system does not heat up under this load. The core component of an automotive ECU is a microcontroller (MCU) with a voltage of 3.3V but a current requirement of only 150mA. When the car is turned off, although the MCU can switch to standby power saving mode, it cannot be completely shut down because it also handles communication and wake-up functions.
For these applications, you can choose to use a low dropout regulator (LDO). As the most cost-effective electronic components, LDOs can provide both low current and a clean power rail for noise-prone microprocessors. But in standby mode, the LDO will be connected directly to the car battery, which will cause the voltage to drop significantly. Since LDOs are not the most efficient way to power a microcontroller, can you suggest some optimizations for the total power consumption?
With the TPS65320C-Q1, you can power the system this way directly from the battery. The product supports input voltages ranging from 3.6V to 36V and has two output rails: a 3.2A buck converter that can convert frequencies from 100kHz to 2.5kHz with 10% conversion accuracy, ; The other is a 289mA LDO. These two rails are integrated into a small 14-pin thin small outline package (HTSSOP).
Taking an LED dome light in a car as an example, you can use a buck converter to power the 5V rail, and the LDO uses the 3.3V rail, as shown in Figure 1. Integrating the two rails into a small chip not only saves space, but also adds a function that improves the power efficiency of the system: LDO automatic power supply. When the buck converter starts working, the switching regulator switches the power output to the LDO, which minimizes voltage drop, power loss, and heat dissipation.
Figure 1: The working module diagram of the car interior dome light in the working state
When the buck converter is inactive, the LDO will remain active and automatically switch to battery voltage, allowing the MCU to remain active when the rest of the system is turned off. The principle is to draw a typical quiescent current of less than 35µA from the LDO, as shown in Figure 2:
Figure 2: Working module diagram of car interior dome light in standby state
You can see similar use cases on almost all in-vehicle devices, including infotainment, advanced driver assistance systems (ADAS), instrument clusters, and body electronics.
Do you have the exact opposite requirement: i.e. 100mA on the 5V rail, but 2A on the 3.3V rail? Stay tuned for the next part of this article where I discuss how a wide VIN integrated buck converter and LDO can power your automotive system.
The Links: LJ640U21 FS50R12KE3