As you get in your car you will be surrounded by more than 100 clocks that monitor you car’s performance keeping you safe and allowing you to enjoy all the comforts, conveniences and infotainment as you travel.
Timing technology is at the heart of every electronic device, from consumer electronics and IoT devices to industrial, medical and in automotive sub-systems.
Present in many automotive applications, the timekeeping function is a key requirement for all data logger type of products. This covers especially the Event Data Recorder (EDR), the diagnostic systems (OBDII), the instrument cluster, the infotainment. With the rise of electrification, they are also heavily present in EV charging systems (EVSE, OBC) and battery management systems (BMS). This is obviously recognized as very useful when the GPS auto-set time function is not active or GPS signal is lost in order to avoid customer complaint but it is necessary for all type of analysis purpose (black- box).
Automotive applications require extended temperature operation, typically in the -40°C to +125°C range. Electronic system location in the vehicle combined to weather conditions as well as heat generated by the engine or battery packs can drive extreme temperature fluctuations, which can degrade the accuracy of timing components.
To comply with time accuracy requirements defined as time deviation per day, it is necessary to apply a compensation to the 32.768 kHz oscillator. The most efficient and market proven approach is to use a Real-Time Clock (RTC) module with embedded temperature compensated oscillator (TCXO).
RV-3032-C7 in BMS
In BMS application, RTC and memory are used, as in many other applications, for black-box purpose. Thus, RTC is used for accurate time stamp and memory is used for storing data collected from battery cells sensors (temperature, voltage, current, etc…). The estimation of the battery pack’s State of Charge (SoC) and State of Health (SoH) are both based on time related information. Accuracy and reliability of such values are key to determine how far the vehicle can go before needing to recharge and to diagnose and take necessary corrective actions or trigger failsafe mechanisms to preserve the health of the pack.
With best accuracy of all temperature compensated RTC at ±2.5 ppm (± 0.22s/day) over the AEC-Q Grade 3 temperature range (-40°C to +85°C); the RV-3032-C7 has also an ultra-low current consumption of 160nA. This high performance RTC comes with a variety of features. An innovative and very useful one for the development of automotive applications being the embedded accurate (±1°C), high-resolution (12-bit) temperature sensor. With its programmable temperature window detection interrupt, it also enables times stamp for temperature alarm event, making it ideal for the detection of thermal runaway or fast temperature change detection. With its 1-second refresh period, this device provides real-time temperature monitoring and can wake up the main module MCU to trigger an alarm when the temperature is not within the required range specified. This help ensuring that appropriate action is taken even when EV is inactive and unplugged. The addition of an ultra-low power and continuous temperature monitoring in the systemprovides also a redundancy option in the system architecture and facilitates design to comply with ISO 26262 ASIL* requirements.
Compliance to AEC-Q200 standard assures automakers that quartz based timing components meet stress resistance linked to automotive, temperature, vibration and shock mission profiles.
By integrating the quartz crystal and the temperature sensor within the ultra-small RTC package, it allows to minimize the footprint.
The RV-3032-C7 is a calibrated device that simplify manufacturing process where a 1-point temperature verification is sufficient.
Moreover, it can be easily interfaced through the same I2C bus used by other sensors and other hardware devices for easy connectivity.
The factory high time accuracy of such RTC eliminates any need for oscillator design & adjustment phase and clock calibration during manufacturing. Selecting and using a ready-to-go RTC module solution in your design reduce engineering effort and risk in building your product while bringing innovation and customer satisfaction within automotive industry.
With its timing and frequency product lines Micro Crystal masters the Art of Timing to meet extreme requirements in terms of size, power consumption, and performance; helping engineers in developing next generations of automotive devices and other smart products. This covers a wide range of compact applications like typically in metering solutions, POS, automation, health & medical devices, wearables and many more.
To find more detailed information and to learn more about how Micro Crystal has the solution for you, please visit microcrystal.com
*ASIL refers to Automotive Safety Integrity Level and is a risk classification for the functional safety of road vehicles