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Reliable Timing is Essential for Telematics

By Kai Ying, Sr. Product Marketing Manager

With more insurers now referring to data provided by telematics boxes (T-Boxes), fitted either by the manufacturer or supplied by the insurance company—the use of T-Boxes is on the rise. Alongside providing independent and verifiable data, T-Boxes are also responsible for the overall connected nature of modern vehicles.

This may include the ability to track and monitor the vehicle online, remotely lock and unlock the vehicle's doors, windows, and luggage space, and control the vehicle's comfort settings. A T-Box may also include other enabling technologies, such as GPS for location services or cellular connectivity.

Although it may have been fitted after purchase, It is important to appreciate that the technology used inside a T-Box needs to be as reliable as any other system in the vehicle. The services a T-Box provides could be critical, such as eCall, but a T-Box may also be closely integrated with other important systems within the vehicle. Using automotive-compliant components, even if not strictly required, is now standard practice because of the reassurance it offers. This is particularly apparent if the T-Box is fitted in the engine bay or otherwise outside of the cockpit.

One of the key functions required for any kind of connectivity is the ability to synchronise operations across network boundaries. This is generally achieved by the protocol encoding a timestamp. Therefore, the need for an accurate real-time clock is likewise critical.

The PT7C4563BQ and PT7C4363BQ are automotive-compliant real-time clock (RTC) devices from Diodes Incorporated, which have been designed to provide a number of functions for automotive applications including T-Boxes, infotainment systems, and dashboards. Qualified to AEC-Q100 Grade 1, they operate over a temperature range of -40 °C to +125 °C and are PPAP capable, as well as being manufactured in facilities certified to IATF16949. They operate from a supply voltage of between 1.3 V and 5.5 V and consume as little as 400 nA when in standby mode.

Each device provides a Binary Coded Decimal (BCD) output that includes the hour, minute, and second; along with year, month, date, and day. They can also generate a square wave output with four frequencies (1Hz, 32Hz, 1024Hz, or 32,768Hz), which can be disabled when not needed, and a programmable interrupt output that is triggered when a predefined time is reached. The devices interface to a host processor through an industry standard I2C port comprising SCL and SDA for clock and data, respectively. An oscillator fail detection feature is also included, with a corresponding flag (OSF).

In addition, the PT7C4363BQ features a timer function, which uses an 8-bit value stored in the device and a clock source of either 4096 Hz, 64 Hz, 1 Hz, or 1/60 Hz to count down from that value to zero. When the timer reaches zero, it sets a flag, TF, which can be read and cleared by the host processor. This TF flag can also be used to assert an interrupt, configured as either a pulsed signal or permanently active signal. Reading the timer will return the current countdown value.

The need for an RTC in automotive applications is growing as vehicles become part of the Internet of Things. Connected cars communicating over wireless interfaces is just one example of why an automotive-compliant RTC is now a critical component for automotive manufacturers. With the introduction of the PT7C4563BQ and PT7C4363BQ, Diodes continues to deliver just what the industry needs.