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What is RTC Modules?
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
- Utility Smart Meters * We show the usage in the white paper for details
- Surveillance Security equipment
- Industrial factory automation / Industry 4.0
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 RTC 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℃.
| 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 |
|
||
| External dimensions | 3.2x2.5x1.0t (Max.)mm | ||
Package Dimensions and Product Features
■ 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 ①②③ |
|||||||
| 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 |
High accuracy Time Stamp +105℃ |
I2C | 0.24 | 32 times | ||||
| RX4901CE |
High accuracy Time Stamp +105℃ |
SPI | 0.24 | 32 times | |||||
| RX8111CE | Low Power Time Stamp +105℃ |
I2C | 0.1 | 8 times | |||||
| RX4111CE | Low Power Time Stamp +105℃ |
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 |
High accuracy up to +125℃ Reset output AEC-Q100 |
I2C | 0.3 | 2 times | ||||
| RA4000CE |
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 | ||||||
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.
