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RTC Modules for Automotive
Are You Struggling with These Problems? 3 Types of Issues for In-vehicle Equipment Epson RTC Module Solves 3 Types of Issues 3 Reasons for Using RTC Module Main Specifications RA4000CE/RA8000CE Package Dimensions and Product Features Recommend Product Lineup Other Documents
What is "RTC"?
"RTC" is an acronym for Real Time Clock, which is an electronic device that measures time.
What is "RTC Module"?
"RTC module" is a single packaged module which integrated RTC IC, oscillator circuit and master clock. There is no need for oscillator circuit design and frequency adjustment by yourselves.
Features of Epson's RTC Module
Are You Struggling with These Problems? 3 Types of Issues for In-vehicle Equipment
1Accuracy of clock gets worse under high temperature conditions...
Due to the increasing functionality of ADAS and autonomous driving, high power SOC with self-heating may significantly elevate the temperature inside the module. In addition, ECU are often installed in high temperature environments (e.g. near the battery).
The 32kHz crystal that is typically used for the clock has a frequency characteristic that shift dramatically with temperature. This frequency shift causes significant the deviation of the time information.
2Back up current consumption cannot meet specifications...
The number of ECUs installed in cars is increasing and have become multifunctional. From this trend, the current consumption during standby mode is also increasing, and to reduce the current consumption of each ECUs is becoming more important year by year.
Requirement of reducing current consumption is strong especially for the ECUs that continue to operate when the vehicle is turned off (e.g. BMS, Battery Management System).
3Redundancy of the system is mandatory to improve safety of equipment...
Redundancy of systems and parts is required are increasing to meet ISO 26262 requirements.
Material costs and mounting space have become issues to accommodate high ASIL levels.
Epson RTC Module Solves 3 Types of Issues
Automotive and high accuracy RTC module RA4000CE and RA8000CE
It is a RTC module with enhanced features which AEC-Q100 qualified and can operate under a high temperature condition (up to 125℃). RA4000CE supports SPI-Bus interface and RA8000CE supports I²C-Bus interface.
Main features of RA4000CE and RA8000CE
♢ High accuracy time information under a high temperature condition up to 125℃.
This product ensure the high accuracy clock during the temperature range from -40℃ to 125℃ due to the D-TCXO function.
♢ Automotive grade quality AEC-Q100.
High automotive quality standard in all processes. (e.g. Design, Manufacturing, Process Control)
♢ Reduced current consumption during system standby mode.
Low current consumption (300nA Typ.)
♢ Contribute to system redundancies and BoM reduction
This product has many optional functions (e.g. reset function, time stamp function etc.)
♢ Available to choose the best one from many options and interfaced (I2C-Bus/SPI-Bus).
This product support I2C-Bus interface and each SPI-Bus interfaces. Also supports various configuration of multiple event pins, time stamps, and other functions.
Features
Use-cases
■ Applications
- BMS (Battery Management System) *We show the usage in the white paper for details.
- Vehicle computer
- Central gateway
- Industrial machine
3 Reasons for Using RTC Module
1Provide High precision time information when the temperature changes
DTCXO (Digital Temperature Compensated Xtal Oscillator) is installed in the RTC module. The RTC module provides highly accurate time information up to 125℃ when the temperature on the customer's board changes.
| Temperature | Existing product (no DTCXO) |
RA8000CE RA4000CE |
|
|---|---|---|---|
| 85℃ | Day | 10.8s | 0.5s |
| Month | 5min 27s | 13.2s | |
| 105℃ | Day | 19.3s | 0.7s |
| Month | 9min 41s | 21s | |
| 125℃ | Day | 31s | 4.4s |
| Month | 15min 7s | 2min 12s | |
2Lowers overall system power
RTC module can keep the time information with one order of magnitude lower current consumption than the sleep mode of the MCU. RTC module can significantly reduce the power of the customer's system.
3A reset function contributes to system redundancy
RTC module detects a drop of the main power supply, and outputs a reset signal to the MCU. This eliminates the need for an external reset IC, which reduces the customer's board space, number of mounted parts, and cost. In addition, Customers who use only the reset function in the MCU can add redundancy to their system by using RTC module reset function.
Common circuit configuration
Epson's proposal
Main Specifications RA4000CE/RA8000CE
| Product Name | RA8000CE | RA4000CE | |
|---|---|---|---|
| Interface | I2C-Bus | SPI-Bus | |
| Interface power voltage | 1.6V to 5.5V | ||
| Time-keeping current consumption | 300nA (Typ.)/3V *without Reset output function | ||
| Operating temperature | -40℃ to +125℃ | ||
| Frequency tolerance | -40℃ to +85℃ | ±5.0 x 10-6 (Monthly rate ±13.2 seconds) | |
| +85℃ to +105℃ | ±8.0 x 10-6 (Monthly rate±21seconds) | ||
| +105℃ to +125℃ | ±50.0 x 10-6(Monthly rate±132seconds) | ||
| Features |
|
||
| Automotive standard conformance | Conforms AEC-Q100 | ||
| External dimensions | 3.2x2.5x1.0t (Max.)mm | ||
Package Dimensions and Product Features
■ External Dimensions
| RA8000CE | RA4000CE | ||||||
|---|---|---|---|---|---|---|---|
| Option A | Option B | Option A | Option B | Option D | Option E | ||
| I/F | I2C | SPI3-wire | SPI4-wire | ||||
| EVIN | 2ch | 2ch | 1ch | ||||
| Reset | No | Yes | No | Yes | No | Yes | |
| Pin# | 1 | EVIN1 | EVIN1 | DI | |||
| 2 | VDD | VDD | VDD | ||||
| 3 | /INT | CE | CE | ||||
| 4 | FOUT | FOUT | /INT | ||||
| 5 | N.C. | /RST | N.C. | /RST | N.C. | /RST | |
| 6 | EVIN2 | EVIN2 | EVIN2 | ||||
| 7 | SDA | DIO | DO | ||||
| 8 | SCL | CLK | CLK | ||||
| 9 | GND | GND | GND | ||||
| 10 | SOUT | /INT | SOUT | ||||
■ Product Name
| RA4000CEYBA0 ①②③④ |
||||||||||
| ① Product Name | ② Frequency Tolerance | ③ Pin* | ④ Reset | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| RA4000CE | SPI-Bus Interface | YB | ±5.0 x 10-6/-40℃ to +85℃ ±8.0 x 10-6/-40℃ to +105℃ ±50 x 10-6/+105℃ to +125℃ |
A | Option A | 0 | No | |||
| B | Option B | |||||||||
| RA8000CE | I2C-Bus Interface | D | Option D | 8 | Yes | |||||
| E | Option E | |||||||||
* Please refer table above for pin options
Recommend Product Lineup
| Grade | Product Name | Features | Interface | Backup current consumption Typ. (3V[µA] |
DTCXO | Function | |||
|---|---|---|---|---|---|---|---|---|---|
| Power Switch | Time Stamp | Event input pin | Others | ||||||
| Industrial Consumer |
RX8901CE |
High accuracy Time Stamp +105℃ |
I2C | 0.24 | 32times | ||||
| RX4901CE |
High accuracy Time Stamp +105℃ |
SPI | 0.24 | 32times | |||||
| RX8111CE | Low Power Time Stamp +105℃ |
I2C | 0.1 | 8times | |||||
| RX4111CE | Low Power Time Stamp +105℃ |
SPI | 0.1 | 8times | |||||
| RX8130CE | Reset output Backup battery charge contro |
I2C | 0.3 | ||||||
| RX8804CE | High accuracy Up tp +105℃ |
I2C | 0.35 | 1times | SOUT Status OUT pin |
||||
| RX8900CE | High accuracy | I2C | 0.7 | ||||||
| Automotive | RA8000CE |
High accuracy up to +125℃ Reset output AEC-Q100 |
I2C | 0.3 | 2times | ||||
| RA4000CE |
High accuracy up to +125℃ Reset output AEC-Q100 |
SPI | 0.3 | 2times | |||||
| RA8804CE | High accuracy up to +125℃ Reset output AEC-Q100 |
I2C | 0.35 | 1times | SOUT Status OUT pin |
||||
| RA8900CE | High accuracy AEC-Q200 |
I2C | 0.7 | ||||||
Other Documents
Application ManualRA4000CERA8000CE
This manual documents the functions, specifications and electrical characteristics.
In addition, it has application notes for the development and using the RA4000CE/RA8000CE product.
White paper: Benefits of RTC Module in an Automotive Battery Management System
It is a document introduces values for customers who mount Epson's RTC module on electrical vehicles BMS.
White paper: kHz-band DTCXO timekeeping accuracy in a temperature changing environment
It is a document that verified that stable time accuracy can be obtained in the kHz band DTCXO in an actual use environment where the outside temperature changes by conducting a long-term actual use test in a car.
