Grade A · Standard
Standard RTC
Integrated crystal · general purpose
The everyday timekeeper. A built-in 32.768 kHz crystal, calendar registers and an alarm — for any system that just needs the date and time over a bus.
Category 03 · Real-Time Clocks
Time that keeps running — even when the power doesn't.
An RTC module counts seconds, minutes and calendar dates on its own, drawing nanoamps from a backup cell. The crystal is built in and pre-trimmed — you read the time over I²C or SPI and move on.
FIG.03 · RTC MODULE
I²C / SPI
Crystal + divider + calendar registers
I < 250 nA
Interface
I²C / SPI
Timekeeping I
< 250 nA
Accuracy
±5 ppm (DTCXO)
Crystal
Integrated
Three Grades
Standard, low-power, DTCXO. Pick by accuracy.
Every RTC counts time — what separates the grades is how far they drift over temperature and how little current they draw. TDE stocks all three across the partner range.
Grade B · Low-Power
Ultra-Low-Power RTC
Nanoamp timekeeping current
When the backup cell has to last for years. Timekeeping current below 250 nA — for battery-backed meters, data loggers and asset trackers that sleep most of their life.
< 250 nATimer / interrupt
Metering / logging
Grade C · DTCXO
High-Accuracy RTC
Digital temperature compensation
When the date has to be right after years unattended. An on-chip DTCXO holds accuracy to ±5 ppm across temperature — for industrial, automotive and gateway timestamps.
±5 ppmDTCXO
Time-stampIndustrial / auto
The Parameters That Matter
Six numbers decide the part.
An RTC datasheet is mostly register maps — but these six lines drive the design-in, from bus choice to how long the backup cell survives.
Parameter
Typical range
Why it matters
Bus interface
I²C · SPI
Must match the host MCU. I²C saves pins; SPI is faster.
Timekeeping current
< 250 nA – 1 µA
Sets backup-cell lifetime — the headline number for battery designs.
Accuracy
±5 – ±23 ppm
Drift over temperature. DTCXO parts hold ±5 ppm; standard parts drift more.
Supply voltage
1.2 – 5.5 V
Wide range eases backup switch-over from main rail to cell.
Functions
Alarm · Timer · Interrupt
An RTC alarm can wake the whole system — key for ultra-low-power designs.
Time-stamp / event
Event input · RAM
Logs an external event with a timestamp — useful for tamper and audit.
On-Chip Functions
More than a clock. A system companion.
A modern RTC carries functions that offload the host MCU — and let it sleep longer.
Calendar
Date to year 2099
Alarm
Wake the system
Timer
Periodic interrupt
Backup
Auto cell switch-over
Time-Stamp
Event logging
Selection Guide
Three steps to the right RTC.
01
Accuracy budget
Decide how far the clock may drift. Consumer timekeeping can run a standard part; industrial timestamps need a DTCXO grade.
→ See the three grades above
02
Power & backup
For battery-backed designs, the timekeeping current sets cell lifetime. Check the supply range and the auto switch-over behaviour.
→ See the spec table above
03
Bus & functions
Match I²C or SPI to your host, then confirm the functions you need — alarm, timer, time-stamp — and a second source.
→ Use the RTC Finder
Where RTCs Run
Anything that has to know the date.
Smart metering
Data loggers
Asset & GPS trackers
IoT gateways
Industrial controllers
Automotive ECUs
Medical devices
Point-of-sale
Security & access
Related Categories
Just need the crystal for an RTC?
If your MCU already has an RTC peripheral, all it needs is a 32.768 kHz crystal — or step up to a clock oscillator for the system timebase.
Ready to specify
Let's keep your calendar running.
Browse RTC modules with pricing and datasheets in the shop — or tell us your accuracy and power budget, and we'll recommend the part.
Category 03 · Real-Time Clocks
Time that keeps running — even when the power doesn't.
An RTC module counts seconds, minutes and calendar dates on its own, drawing nanoamps from a backup cell. The crystal is built in and pre-trimmed — you read the time over I²C or SPI and move on.
FIG.03 · RTC MODULE
I²C / SPI
Crystal + divider + calendar registers
I < 250 nA
Interface
I²C / SPI
Timekeeping I
< 250 nA
Accuracy
±5 ppm (DTCXO)
Crystal
Integrated
Three Grades
Standard, low-power, DTCXO. Pick by accuracy.
Every RTC counts time — what separates the grades is how far they drift over temperature and how little current they draw. TDE stocks all three across the partner range.
Grade A · Standard
Standard RTC
Integrated crystal · general purpose
The everyday timekeeper. A built-in 32.768 kHz crystal, calendar registers and an alarm — for any system that just needs the date and time over a bus.
±23 ppmI²C / SPI
AlarmConsumer / IoT
Grade B · Low-Power
Ultra-Low-Power RTC
Nanoamp timekeeping current
When the backup cell has to last for years. Timekeeping current below 250 nA — for battery-backed meters, data loggers and asset trackers that sleep most of their life.
< 250 nATimer / interrupt
Metering / logging
Grade C · DTCXO
High-Accuracy RTC
Digital temperature compensation
When the date has to be right after years unattended. An on-chip DTCXO holds accuracy to ±5 ppm across temperature — for industrial, automotive and gateway timestamps.
±5 ppmDTCXO
Time-stampIndustrial / auto
The Parameters That Matter
Six numbers decide the part.
An RTC datasheet is mostly register maps — but these six lines drive the design-in, from bus choice to how long the backup cell survives.
Parameter
Typical range
Why it matters
Bus interface
I²C · SPI
Must match the host MCU. I²C saves pins; SPI is faster.
Timekeeping current
< 250 nA – 1 µA
Sets backup-cell lifetime — the headline number for battery designs.
Accuracy
±5 – ±23 ppm
Drift over temperature. DTCXO parts hold ±5 ppm; standard parts drift more.
Supply voltage
1.2 – 5.5 V
Wide range eases backup switch-over from main rail to cell.
Functions
Alarm · Timer · Interrupt
An RTC alarm can wake the whole system — key for ultra-low-power designs.
Time-stamp / event
Event input · RAM
Logs an external event with a timestamp — useful for tamper and audit.
On-Chip Functions
More than a clock. A system companion.
A modern RTC carries functions that offload the host MCU — and let it sleep longer.
Calendar
Date to year 2099
Alarm
Wake the system
Timer
Periodic interrupt
Backup
Auto cell switch-over
Time-Stamp
Event logging
Selection Guide
Three steps to the right RTC.
01
Accuracy budget
Decide how far the clock may drift. Consumer timekeeping can run a standard part; industrial timestamps need a DTCXO grade.
→ See the three grades above
02
Power & backup
For battery-backed designs, the timekeeping current sets cell lifetime. Check the supply range and the auto switch-over behaviour.
→ See the spec table above
03
Bus & functions
Match I²C or SPI to your host, then confirm the functions you need — alarm, timer, time-stamp — and a second source.
→ Use the RTC Finder
Where RTCs Run
Anything that has to know the date.
Smart metering
Data loggers
Asset & GPS trackers
IoT gateways
Industrial controllers
Automotive ECUs
Medical devices
Point-of-sale
Security & access
Related Categories
Just need the crystal for an RTC?
If your MCU already has an RTC peripheral, all it needs is a 32.768 kHz crystal — or step up to a clock oscillator for the system timebase.
Ready to specify
Let's keep your calendar running.
Browse RTC modules with pricing and datasheets in the shop — or tell us your accuracy and power budget, and we'll recommend the part.