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. 912-2774
Mfr. Part No.MCP7940N-I/SN
BrandMicrochip
R 11.163
Each (In a Tube of 100)
units
Battery Backup, Calendar DW:DM:M:Y HH:MM:SS 64B 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. 880-5342
Mfr. Part No.M41T62LC6F
R 63.238
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. 803-2187
Mfr. Part No.MCP79521-I/MS
BrandMicrochip
R 19.104
Each (In a Pack of 5)
units
Calendar DW:M:Y:LY HH:MM:SS:HSS 64B Serial Surface Mount MSOP 10 3 x 3 x 0.95mm 3mm 3mm 0.95mm 3.6 V +85 °C
RS stock no. 146-0221
Mfr. Part No.MCP79521-I/MS
BrandMicrochip
R 17.927
Each (In a Tube of 100)
units
Calendar DW:M:Y:LY HH:MM:SS:HSS 64B Serial Surface Mount MSOP 10 3 x 3 x 0.95mm 3mm 3mm 0.95mm 3.6 V +85 °C
RS stock no. 165-2099
Mfr. Part No.MCP79510-I/MS
BrandMicrochip
R 16.80
Each (In a Tube of 100)
units
Calendar DW:M:Y:LY HH:MM:SS:HSS 64B Serial-SPI Surface Mount MSOP 10 3 x 3 x 0.95mm 3mm 3mm 0.95mm 3.6 V +85 °C
RS stock no. 920-9120
Mfr. Part No.M41T00M6F
R 23.019
Each (On a Reel of 2500)
units
Calendar D:M:Y:C HH:MM:SS 8B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS stock no. 920-9133
Mfr. Part No.M41T81SM6F
R 20.96
Each (On a Reel of 2500)
units
Calendar D:D:M:Y:C HH:MM:SS:HSS 20B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS stock no. 825-1076
Mfr. Part No.MCP79510-I/MS
BrandMicrochip
R 18.54
Each (In a Pack of 5)
units
Calendar DW:M:Y:LY HH:MM:SS:HSS 64B Serial-SPI Surface Mount MSOP 10 3 x 3 x 0.95mm 3mm 3mm 0.95mm 3.6 V +85 °C
RS stock no. 159-7452
Mfr. Part No.MCP79520-I/MS
BrandMicrochip
R 17.996
Each (In a Tube of 100)
units
Calendar DW:M:Y:LY HH:MM:SS:HSS 64B Serial Surface Mount MSOP 10 3 x 3 x 0.95mm 3mm 3mm 0.95mm 3.6 V +85 °C
RS stock no. 686-5036
Mfr. Part No.M48T58-70PC1
R 315.66
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. 829-0380
Mfr. Part No.M41T00M6F
R 44.362
Each (In a Pack of 5)
units
Calendar D:M:Y:C HH:MM:SS 8B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS stock no. 723-4749
Mfr. Part No.MCP79410-I/MS
BrandMicrochip
R 16.495
Each (In a Pack of 2)
units
Battery Backup, Calendar, NV SRAM DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount MSOP 8 3 x 3 x 0.95mm 3mm 3mm 0.95mm 5.5 V +85 °C
RS stock no. 169-8137
Mfr. Part No.Q41454351000111
BrandEPSON
R 42.956
Each (On a Reel of 250)
units
Calendar, Timer - - - Serial Surface Mount SOP 14 5 x 10.1 x 3.2mm 5mm 10.1mm 3.2mm 5.5 V +85 °C
RS stock no. 797-9458
Mfr. Part No.DS1338Z-18+
R 57.475
Each (In a Pack of 2)
units
Calendar YY:MM:DD HH:MM:SS 56B Serial-2 Wire, Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS stock no. 729-3375
Mfr. Part No.RV-8564-C2-TA-020
R 60.60
Each
units
Calendar DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount SON 10 5 x 3.2 x 1.2mm 5mm 3.2mm 1.2mm 5.5 V +85 °C
RS stock no. 732-7355
Mfr. Part No.DS1337U+
R 54.22
Each
units
Calendar DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount μSOP 8 3.1 x 3.1 x 0.95mm 3.1mm 3.1mm 0.95mm 5.5 V +85 °C
RS stock no. 189-8359
Mfr. Part No.DS1672S-33+
R 50.426
Each (In a Pack of 5)
units
Battery Backup, Calendar DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS stock no. 189-8692
Mfr. Part No.DS1390U-33+
R 61.612
Each (In a Pack of 5)
units
Battery Backup, Calendar, NV RAM DW:DM:M:Y HH:MM:SS - Serial-SPI Surface Mount μSOP 10 3.05 x 3.05 x 0.95mm 3.05mm 3.05mm 0.95mm 5.5 V +85 °C
RS stock no. 191-6894
Mfr. Part No.DS1685S-5+
R 97.45
Each (In a Pack of 2)
units
NV SRAM, Real Time Clock - - 242B Multiplexed Surface Mount SO 24 15.6 x 7.6 x 2.35mm 15.6mm 7.6mm 2.35mm 5.5 V +70 °C
RS stock no. 191-3504
Mfr. Part No.DS1339AU+
R 62.315
Each (In a Pack of 2)
units
Real Time Clock D:D:M:Y SS:MM:HH - Serial-I2C Surface Mount μSOP 8 3.1 x 0.65 x 0.95mm 3.1mm 0.65mm 0.95mm 5.5 V +85 °C