Adapting different subsystems using low voltage level shifters

In the past, car infotainment systems were mainly powered by 5V and 3.3V power supplies. The reason is that there are ready-to-use 12-14V batteries in the automotive system that can be stepped down to a lower voltage level. However, several key factors have driven the need for lower voltage operation in infotainment, advanced driver assistance systems (ADAS) and cluster systems.

Over the past decade, mobile and computing systems technologies have evolved dramatically, providing technological advancements and feature-rich user experiences that enable multiple audio and video access. Consumers are eager to achieve the same content and functionality in their car infotainment system. The way to achieve this before is a Bluetooth-enabled touchscreen, and the current implementation is a multi-touch tablet-sized display that supports Internet access, high-definition multimedia interface (HDMI) and USB.

Automotive Tier 1 manufacturers are taking advantage of the electronic infrastructure that has been built for mobile and computing functions and giving them new uses for automotive infotainment and cluster systems. These increasingly complex systems are delivered in a modular fashion, and original equipment manufacturers (OEMs) can select features based on the level of the vehicle. In order to maximize the reuse of these mixed mode voltage systems, a voltage level shifter is required to connect these different subsystems together.

There are two main problems when docking a 3.3V device to a previous 5V system. The VOH of the 3.3V system cannot meet the VIH threshold voltage required by the 5V system, and the VOL of the 5V system cannot meet the VIL requirements of the 3.3V system. In systems with lower voltages, this problem becomes more subtle due to the smaller incompatibility of VOH/VIH and VOL/VIL. At the beginning, the device seems to be able to communicate, but communication is stopped due to small differences between VOL and VIL. In these extended vehicle temperature ranges, the problem of threshold mismatch will appear.

To solve this problem, engineers can use products from the full line of Texas Instruments' automotive-grade voltage level shifters. The SN74LVCxxT245-Q1, SN74AVCxxT245-Q1, TXB010x-Q1 and TXS010x-Q1 series are ideal for leveling this voltage mismatch. The "x" in it indicates the number of bits or channels that need to be converted. Depending on the type of output (push, pull or open drain), load conditions and signal direction, a suitable solution can be used to "level shift" to the desired voltage.

The SN74LVCxxT245-Q1 and SN74AVCxxT245-Q1 series are ideal for loading larger buses with multiple devices connected. These devices deliver up to 12mA and are specifically designed to drive loads up to 15pF. In this case, the main controller will need to control the data flow of the device.

The TXB010x-Q1 family of devices is used in those mixed voltage/mixed direction bus applications. This type of device eliminates the need for host processor intervention, making it a plug-and-play, fully self-contained solution. However, due to their relatively low current drive capability, these devices are more suitable for point-to-point bus applications.

Much like the TXB010x-Q1 series, the TXS010x-Q1 requires no processor intervention, but it is designed for open-drain applications such as I2C, or a reset/interrupt pin with an external pull-up voltage.

The next-generation "start-stop" system has a battery voltage below 3V. This also speeds up the migration to lower voltage subsystems. Whether it is an infotainment system, a cluster system or an ADAS, the need for voltage level shifters is always there.