What is RTC Modules? - Solutions for Improving Time Accuracy and Lowering System Power for Automotive Application -

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

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.

Frequency Temperature Characteristics
Comparison of Time Deviation
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
  • Reset output(optional)
  • Time Stamp: record 1/1024 to years data, 2 events
  • A binary counter for counting seconds such as UNIX time is included.
Automotive standard conformance Conforms AEC-Q100
External dimensions 3.2x2.5x1.0t (Max.)mm

Package Dimensions and Product Features

■ External Dimensions

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
 
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
New
High accuracy Time Stamp I2C 0.24 32times  
RX4901CE
New
High accuracy Time Stamp SPI 0.24 32times  
RX8111CE Low Power Time Stamp I2C 0.1   8times  
RX4111CE Low Power Time Stamp 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
New
High accuracy up to +125℃
Reset output AEC-Q100
I2C 0.3   2times  
RA4000CE
New
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      

RX4901CE/RX8901CE What is "RTC Module"? Solutions for Lowering System Power and Improving Time Accuracy

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.

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