Real Time Clocks

What is a Real Time Clock?

A Real Time Clock (RTC) is a computer clock which is usually in the form of an integrated circuit. They have been designed to keep track of time, in real time - hence the product name. A Real Time Clock is usually an integral part of the computer motherboard. More often than not, an RTC will also include a calendar and an alarm

How do Real Time Clocks work?

The memory on the clocks system stores system descriptions and set up values such as "Current Time Value". The information that is held in the RTC is read with a microprocessor, commonly over a serial interface which facilitates the performance of the software functions that are time dependant.

Designed to run on ultra-low power consumption, RTCs often run on a lithium battery source but can also run on normal power. This power source allows them to continue running and generating real time when a system is down. The newer models of RTC use super-capacitors as a source of power that can be recharged and soldered to the board. Some Real Time Clocks feature synchronisation to an external signal, such as a compensated power line frequency. It allows the device to provide an accurate result without having an on-board temperature compensation scheme.

RTC Time Values

  • Year
  • Month
  • Date
  • Hours
  • Minutes
  • Seconds

...
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Description Price Functions Date Format Time Format User RAM Bus Type Mounting Type Package Type Pin Count Dimensions Length Width Height Maximum Operating Supply Voltage Maximum Operating Temperature
RS Stock No. 124-2362
Mfr. Part No.PCF8563T/5,518
BrandNXP
£0.577
Each (On a Reel of 2500)
Units
Calendar, Clock YY:MM:DD:dd HH:MM:SS - Serial-2 Wire, Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.45mm 5mm 4mm 1.45mm 5.5 V +85 °C
RS Stock No. 865-2208
Mfr. Part No.PCF8563T/5,518
BrandNXP
£0.599
Each (In a Pack of 10)
Units
Calendar, Clock YY:MM:DD:dd HH:MM:SS - Serial-2 Wire, Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.45mm 5mm 4mm 1.45mm 5.5 V +85 °C
RS Stock No. 732-7333
Mfr. Part No.DS1307ZN+
£3.03
Each
Units
Calendar DW:DM:M:Y HH:MM:SS 56B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS Stock No. 889-5121
Mfr. Part No.MCP79410-I/SN
BrandMicrochip
£0.625
Each (In a Tube of 100)
Units
Battery Backup, Calendar, Clock, NV Timekeeping SRAM DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.25mm 4.9mm 3.9mm 1.25mm 5.5 V +85 °C
RS Stock No. 726-3949
Mfr. Part No.MCP79410-I/SN
BrandMicrochip
£0.686
Each (In a Pack of 5)
Units
Battery Backup, Calendar, NV SRAM DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.25mm 4.9mm 3.9mm 1.25mm 5.5 V +85 °C
RS Stock No. 817-3658
Mfr. Part No.MCP79410T-I/SN
BrandMicrochip
£0.625
Each (On a Reel of 3300)
Units
Alarm, Battery Backup, Calendar, Clock DW:D:M:Y HH:MM:SS 64B Serial-2 Wire, Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.5mm 4.9mm 3.9mm 1.5mm 5.5 V +85 °C
RS Stock No. 165-5507
Mfr. Part No.M41T62LC6F
£1.848
Each (On a Reel of 1000)
Units
Alarm, Calendar, Real Time Clock, Square Wave Output, Watchdog Timer Binary, D:D:M:Y:C Binary, HH:MM:SS 16B Serial Surface Mount CLCC 8 3.3 x 1.6 x 0.8mm 3.3mm 1.6mm 0.8mm 4.4 V +85 °C
RS Stock No. 880-5342
Mfr. Part No.M41T62LC6F
£2.938
Each (In a Pack of 5)
Units
Alarm, Calendar, Real Time Clock, Square Wave Output, Watchdog Timer Binary, D:D:M:Y:C Binary, HH:MM:SS 16B Serial Surface Mount CLCC 8 3.3 x 1.6 x 0.8mm 3.3mm 1.6mm 0.8mm 4.4 V +85 °C
RS Stock No. 624-8466
Mfr. Part No.M48T35Y-70PC1
£19.50
Each
Units
Battery Backup, Calendar, Chip Deselect, Switch Over, Write Protection DW:DM:M:Y HH:MM:SS 32768B Parallel Through Hole PCDIP 28 39.88 x 18.34 x 8.89mm 39.88mm 18.34mm 8.89mm 5.5 V +70 °C
RS Stock No. 920-9001
Mfr. Part No.M48T35Y-70PC1
£17.983
Each (In a Tube of 12)
Units
Battery Backup, Calendar, Chip Deselect, Switch Over, Write Protection DW:DM:M:Y HH:MM:SS 32768B Parallel Through Hole PCDIP 28 39.88 x 18.34 x 8.89mm 39.88mm 18.34mm 8.89mm 5.5 V +70 °C
RS Stock No. 624-8438
Mfr. Part No.M41T62Q6F
£1.45
Each (In a Pack of 5)
Units
Alarm, Battery Backup, Calendar, Watchdog Timer DW:DM:M:Y HH:MM:SS:hh 16B Serial-I2C Surface Mount QFN 16 3 x 3 x 0.88mm 3mm 3mm 0.88mm 4.4 V +85 °C
RS Stock No. 920-9007
Mfr. Part No.M41T62Q6F
£0.738
Each (On a Reel of 3000)
Units
Alarm, Battery Backup, Calendar, Watchdog Timer DW:DM:M:Y HH:MM:SS:hh 16B Serial-I2C Surface Mount QFN 16 3 x 3 x 0.88mm 3mm 3mm 0.88mm 4.4 V +85 °C
RS Stock No. 920-8991
Mfr. Part No.M48T58Y-70PC1
£12.209
Each (In a Tube of 12)
Units
Battery Backup, Calendar, Chip Deselect, Switch Over, Write Protection DW:DM:M:Y HH:MM:SS 8192B Parallel Through Hole PCDIP 28 39.88 x 18.34 x 8.89mm 39.88mm 18.34mm 8.89mm 5.5 V +70 °C
RS Stock No. 686-5030
Mfr. Part No.M48T58Y-70PC1
£13.28
Each
Units
Battery Backup, Calendar, Chip Deselect, Switch Over, Write Protection DW:DM:M:Y HH:MM:SS 8192B Parallel Through Hole PCDIP 28 39.88 x 18.34 x 8.89mm 39.88mm 18.34mm 8.89mm 5.5 V +70 °C
RS Stock No. 919-6337
Mfr. Part No.M48T18-100PC1
£13.801
Each (In a Tube of 12)
Units
Battery Backup, Calendar, Chip Deselect, Switch Over, Write Protection DW:DM:M:Y HH:MM:SS 8192B Parallel Through Hole PCDIP 28 39.88 x 18.34 x 8.89mm 39.88mm 18.34mm 8.89mm 5.5 V +70 °C
RS Stock No. 714-7298
Mfr. Part No.M48T18-100PC1
£15.01
Each
Units
Battery Backup, Calendar, Chip Deselect, Switch Over, Write Protection DW:DM:M:Y HH:MM:SS 8192B Parallel Through Hole PCDIP 28 39.88 x 18.34 x 8.89mm 39.88mm 18.34mm 8.89mm 5.5 V +70 °C
RS Stock No. 165-2002
Mfr. Part No.MCP79400-I/SN
BrandMicrochip
£0.565
Each (In a Tube of 100)
Units
Calendar DW:DM:M:Y HH:MM:SS 64B Serial-2 Wire, Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.5mm 4.9mm 3.9mm 1.5mm 2.5 V +85 °C
RS Stock No. 823-0776
Mfr. Part No.MCP79400-I/SN
BrandMicrochip
£0.626
Each (In a Pack of 10)
Units
Calendar DW:DM:M:Y HH:MM:SS 64B Serial-2 Wire, Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.5mm 4.9mm 3.9mm 1.5mm 2.5 V +85 °C
RS Stock No. 686-5036
Mfr. Part No.M48T58-70PC1
£14.10
Each
Units
Battery Backup, Calendar, Chip Deselect, Switch Over, Write Protection DW:DM:M:Y HH:MM:SS 8192B Parallel Through Hole PCDIP 28 39.88 x 18.34 x 8.89mm 39.88mm 18.34mm 8.89mm 5.5 V +70 °C
RS Stock No. 729-3215
Mfr. Part No.RV-3029-C2-TA-006
£10.12
Each
Units
Battery Backup, Calendar, RAM DW:DM:M:Y HH:MM:SS 8B Serial-I2C Surface Mount SON 10 5 x 3.2 x 1.2mm 5mm 3.2mm 1.2mm 5.5 V +85 °C