What is "RTC Module"? - Solutions for Lowering System Power and Improving Time Accuracy -

Are You Struggling with These Problems? 3 Types of Issues Epson RTC Module Can Solve Epson RTC Module Solves 3 Types of Issues 3 Reasons for Using RTC Module Main Specifications RX4901CE/RX8901CE 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 Epson RTC Module Can Solve

1Back up current consumption cannot meet specifications...

The trend of a reduction of current consumption is getting stronger in many IoT applications.

For a Smart Utility Meter, the tamper detect function is often required for security. However, if the microcontroller operates every time for the tamper detection, the system current consumption may be high. RTC can take over many of the house keeping functions at a much lower power.

2Data retention of time information is too short with the back up battery...

To keep the correct time information during a power failure is a requirement.

Higher capacity battery may not be an option due to space constrains or cost.

3Accuracy of clock gets worse under extreme temperature conditions...

High accuracy clock needs is increasing for Smart Utility Meters. Power utility companies use time-base to charge customers.

Smart Utility Meters are often exposed to extreme weather conditions, the RTC maintains a higher accuracy clock over the wide temperature range.

For industrial applications, the high operation temperature is needed for the RTC module. That is due to highly elevated temperature inside the equipment.

Epson RTC Module Solves 3 Types of Issues

High accuracy and low power consumption RX8901CE and RX4901CE

It is a RTC module with enhanced features and operate under a wide temperature range (-40 to 105℃). RX8901CE supports I2C-Bus interface and RX4901CE supports SPI-Bus interface.

Main features of RX8901CE and RX4901CE

♢ Extended operations from a back-up battery

Low current consumption (240nA Typ.)

♢ Record time stamps from up to 3 Types of sensors.

Time stamps can be recorded up to 32 times and up to 3 inputs can be supported.

♢ High accuracy time information at elevated temperature condition (up to 105℃).

With the D-TCXO function, it can provide high accuracy clock over a wide operating temperature range (-40 to 105℃)

♢ Versatility - Selection of interface (I2C/SPI) and multiple other functions

Supports I2C-Bus or SPI-Bus interface standards. Also supports various configuration of multiple event pins, time stamps, and other functions

Features

Use-cases

■ Applications

3 Reasons for Using RTC Module

1Reduce standby power and lower system power

The Time Stamp function stores the time information when an event (signal) is detected. The Real Time Clock module puts the MCU in a low power sleep state, thus reducing the power consumption of the entire system.

Common circuit configuration

Epson's proposal

2Power switch function for efficient use of backup power supply

RTC module detects a voltage drop of the main power supply and automatically switches to a backup power supply for operation. while the MOS switch suppresses leakage current and voltage drops, enabling efficient power management of the entire system compared to diode OR circuits.

Epson's proposal

3Provide 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 105℃.

Frequency Temperature Characteristics
Comparison of Time Deviation
Temperature Existing product
(no DTCXO)
RX8901CE
(XS)
RX4901CE
(XS)
85℃ Day 10.8s 0.3s
Month 5min 27s 8.0s
105℃ Day 19.3s 0.5s
Month 9min 41s 13.2s

Main Specifications RX4901CE/RX8901CE

Product Name RX8901CE RX4901CE
Interface I2C-Bus SPI-Bus
Interface power voltage 1.6V to 5.5V
Backup power voltage 1.1V to 5.5V
Current consumption at backup 240nA(Typ.)/3V
Operating temperature -40℃ to +105℃
Frequency tolerance XS ±3.0 x 10-6 / -40℃ to +85℃ (Monthly rate ±8 seconds)
±5.0 x 10-6 / -40℃ to +105℃ (Monthly rate ±13.2 seconds)
XB ±5.0 x 10-6 / -40℃ to +85℃ (Monthly rate ±13.2 seconds)
±8.0 x 10-6 / -40℃ to +105℃ (Monthly rate ±21 seconds)
Features
  • Auto power switching function
  • Time Stamp: record 1/1024 to years data, max. 32 events
  • Wakeup timer: 976µs to 32years cycle
External dimensions 3.2x2.5x1.0t (Max.)mm

Package Dimensions and Product Features

■ External Dimensions

External Dimensions
RX8901CE RX4901CE
Option A Option B Option A Option B Option C Option D
I/F I2C SPI3-wire SPI4-wire
EVIN 2ch 3ch 1ch 2ch 0ch 1ch
Pin# 1 VDD VDD VDD
2 VOUT VOUT VOUT
3 VBAT VBAT VBAT
4 FOUT EVIN3 FOUT EVIN3 FOUT EVIN3
5 SCL CLK CLK
6 EVIN1 CE CE
7 SDA DIO DO
8 /INT /INT /INT
9 GND GND GND
10 EVIN2 EVIN2 DI

■ Product Name

RX4901CEXSA0
 
① Product Name   ② Frequency Tolerance   ③ Pin*
RX4901CE SPI-Bus Interface XS ±3.0 x 10-6/-40℃ to +85℃
±5.0 x 10-6/-40℃ to +105℃
A0 Option A
B0 Option B
RX8901CE I2C-Bus Interface XB ±5.0 x 10-6/-40℃ to +85℃
±8.0 x 10-6/-40℃ to +105℃
C0 Option C
D0 Option D

* 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 32 times  
RX4901CE
New
High accuracy Time Stamp SPI 0.24 32 times  
RX8111CE Low Power Time Stamp I2C 0.1   8 times  
RX4111CE Low Power Time Stamp SPI 0.1   8 times    
RX8130CE Reset output Backup battery charge contro I2C 0.3        
RX8804CE High accuracy
+105℃
I2C 0.35   1 times 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   2 times  
RA4000CE
New
High accuracy up to +125℃ Reset output AEC-Q100 SPI 0.3   2 times  
RA8804CE High accuracy
+105℃
AEC-Q100
I2C 0.35   1 times SOUT
Status OUT pin
RA8900CE High accuracy
AEC-Q100
I2C 0.7      

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

Other Documents

Application ManualRX4901CERX8901

This manual documents the functions, specifications, and electrical characteristics.
In addition, it has application notes for the development and using the RX4901CE/RX8901CE product.

White paper: Tamper Detection using a RTC Module

The tamper detect function is introduced as an example of installing an RTC module with a multi-EVIN pin function.

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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