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. 190-4752
Mfr. Part No.DS3232SN#T&R
HK$50.022
Each (On a Reel of 1000)
units
Alarm, SRAM DM:M:DW:Y SS:MM:HH 236B Serial-I2C Surface Mount SO 20 13 x 7.6 x 2.35mm 13mm 7.6mm 2.35mm 5.5 V +85 °C
RS Stock No. 171-1637
Mfr. Part No.RV-2123-C2-STD-020
HK$60.022
Each (On a Tape of 100)
units
Alarm, Calendar, Timer DW:DM:M:Y HH:MM:SS - Serial-SPI Surface Mount SON 10 5 x 3.2 x 1.2mm 5mm 3.2mm 1.2mm 5.5 V +85 °C
RS Stock No. 169-8135
Mfr. Part No.Q42724231000611
BrandEPSON
HK$57.224
Each (In a Tube of 25)
units
Calendar, Timer - - - Serial-I2C Surface Mount SOP 24 16.3 x 7.9 x 2.8mm 16.3mm 7.9mm 2.8mm 5.5 V +85 °C
RS Stock No. 798-5254
Mfr. Part No.MCP7940N-I/MS
BrandMicrochip
HK$6.941
Each (In a Pack of 10)
units
Battery Backup, Calendar 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. 798-5258
Mfr. Part No.MCP7940N-I/SN
BrandMicrochip
HK$7.13
Each (In a Pack of 10)
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. 189-7225
Mfr. Part No.DS1338Z-33+
HK$25.253
Each (In a Tube of 100)
units
Battery Backup, Calendar, NV RAM 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. 189-8385
Mfr. Part No.DS17887-5+
HK$174.02
Each
units
Alarm, Calendar YY:MM:DD HH:MM:SS 114B Multiplexed Through Hole EDIP 24 38.1 x 18.29 x 10.67mm 38.1mm 18.29mm 10.67mm 5.5 V +70 °C
RS Stock No. 189-7206
Mfr. Part No.DS1305E+
HK$44.299
Each (In a Tube of 74)
units
Alarm, Calendar DW:DM:M:Y HH:MM:SS 96B Serial-SPI Surface Mount TSSOP 20 6.5 x 4.4 x 0.9mm 6.5mm 4.4mm 0.9mm 5.5 V +70 °C
RS Stock No. 190-4740
Mfr. Part No.DS1374U-18+
HK$29.201
Each (In a Tube of 50)
units
Binary Counter, Real Time Clock, Trickle Charger - - - Serial-I2C Surface Mount μSOP 10 3.16 x 3.12 x 0.95mm 3.16mm 3.12mm 0.95mm 1.89 V +85 °C
RS Stock No. 189-7226
Mfr. Part No.DS1339C-33#
HK$48.426
Each (In a Tube of 46)
units
Battery Backup, Calendar DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount SOIC 16 10.5 x 7.6 x 2.35mm 10.5mm 7.6mm 2.35mm 5.5 V +85 °C
RS Stock No. 196-9064
Mfr. Part No.ISL12022IBZ
HK$36.477
Each (In a Tube of 98)
units
- DW:DM:M:Y HH:MM:SS - - - SOIC 8 - - - - - -
RS Stock No. 189-7245
Mfr. Part No.DS1746-70+
HK$285.988
Each (In a Tube of 11)
units
Calendar YY:MM:DD HH:MM:SS 128 x 8bit Parallel Through Hole EDIP 32 44.2 x 18.8 x 10.92mm 44.2mm 18.8mm 10.92mm 0.8 V, 5.3 V +70 °C
RS Stock No. 667-6243
Mfr. Part No.Q41457451000200
BrandEPSON
HK$27.91
Each
units
Alarm, 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. 732-7582
Mfr. Part No.DS3231SN#
HK$90.66
Each
units
Battery Backup, Calendar DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount SOIC 16 10.5 x 7.6 x 2.35mm 10.5mm 7.6mm 2.35mm 5.5 V +85 °C
RS Stock No. 189-7198
Mfr. Part No.DS1302N+
HK$32.256
Each (In a Tube of 50)
units
Trickle Charger DM:M:DW:Y SS:MM:HH 31B Serial-3 Wire Through Hole PDIP 8 9.91 x 7.87 x 4.45mm 9.91mm 7.87mm 4.45mm 5.5 V +85 °C
RS Stock No. 189-7213
Mfr. Part No.DS1307N+
HK$32.078
Each (In a Tube of 50)
units
Clock DM:M:DW:Y SS:MM:HH 56B Serial-I2C Through Hole PDIP 8 9.91 x 7.87 x 4.45mm 9.91mm 7.87mm 4.45mm 5.5 V +85 °C
RS Stock No. 189-7194
Mfr. Part No.DS12887+
HK$84.903
Each (In a Tube of 14)
units
Alarm, Battery Backup, Calendar, Power Fail Binary, DW:DM:M:Y Binary, HH:MM:SS 114B Multiplexed Through Hole EDIP 24 34.04 x 18.8 x 9.4mm 34.04mm 18.8mm 9.4mm 5.5 V +70 °C
RS Stock No. 714-7298
Mfr. Part No.M48T18-100PC1
HK$193.18
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. 169-8345
Mfr. Part No.ISL12022IBZ
BrandIntersil
HK$32.77
Each (In a Tube of 98)
units
Alarm, Battery Backup, Calendar, Switch Over DW:DM:M:Y HH:MM:SS 128B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS Stock No. 190-5205
Mfr. Part No.DS1744-70IND+
HK$339.25
Each
units
NV SRAM, Real Time Clock Y:M:D:D HH:MM:SS - - Through Hole EDIP 28 39.37 x 18.80 x 10.67mm 39.37mm 18.8mm 10.67mm 5 V +85 °C