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. 798-5260
Mfr. Part No.MCP79412-I/SN
BrandMicrochip
HK$8.694
Each (In a Pack of 5)
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. 171-0508
Mfr. Part No.AB0805-T3
BrandAbracon
HK$14.47
Each (In a Pack of 5)
units
- - - - - Surface Mount 16-VFQFN - - - - - - 85 °C
RS Stock No. 191-3287
Mfr. Part No.DS1340C-33#T&R
HK$29.601
Each (On a Reel of 1000)
units
Clock, Real Time Clock, Trickle Charger D:D:M:Y SS:MM:HH - Serial-I2C Surface Mount SO 16 10.5 x 7.6 x 2.35mm 10.5mm 7.6mm 2.35mm 5.5 V +85 °C
RS Stock No. 191-6894
Mfr. Part No.DS1685S-5+
HK$54.81
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. 723-4749
Mfr. Part No.MCP79410-I/MS
BrandMicrochip
HK$8.335
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. 190-4744
Mfr. Part No.DS1672U-33+
HK$24.171
Each (In a Tube of 50)
units
Binary Counter, Real Time Clock - - - 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
RS Stock No. 177-0776
Mfr. Part No.MCP79401-I/SN
BrandMicrochip
HK$8.085
Each (In a Pack of 10)
units
- D:M:Y, DW HH:MM:SS - 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. 188-9206
Mfr. Part No.M41T82RM6F
HK$11.895
Each (On a Reel of 2500)
units
Alarm, Battery Backup, Calendar, Watchdog Timer Binary, D:D:M:Y:C - 32bit Serial-2 Wire, Serial-I2C Surface Mount SO 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS Stock No. 803-2187
Mfr. Part No.MCP79521-I/MS
BrandMicrochip
HK$11.35
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. 189-8356
Mfr. Part No.DS3232MZ+
HK$72.87
Each
units
Calendar DD:M:Y SS:MM:HH 236B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 4.5 V +85 °C
RS Stock No. 189-8595
Mfr. Part No.DS1305+
HK$54.29
Each (In a Pack of 2)
units
Alarm, Calendar DW:DM:M:Y HH:MM:SS 96B Serial-SPI Through Hole PDIP 16 19.43 x 7.87 x 4.45mm 19.43mm 7.87mm 4.45mm 5.5 V +70 °C
RS Stock No. 190-4749
Mfr. Part No.DS3231S#T&R
HK$42.387
Each (On a Reel of 1000)
units
Real Time Clock DM:M:DW:Y SS:MM:HH - Serial-I2C Surface Mount SO 16 10.5 x 7.6 x 2.35mm 10.5mm 7.6mm 2.35mm 5.5 V +70 °C
RS Stock No. 190-4731
Mfr. Part No.DS1338U-33+T&R
HK$16.80
Each (On a Reel of 3000)
units
NV SRAM, Real Time Clock DM:M:DW: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
RS Stock No. 920-9133
Mfr. Part No.M41T81SM6F
HK$14.125
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. 726-3949
Mfr. Part No.MCP79410-I/SN
BrandMicrochip
HK$8.066
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. 169-8135
Mfr. Part No.Q42724231000611
BrandEPSON
HK$56.387
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. 192-1505
Mfr. Part No.DS1305N+
HK$59.03
Each (In a Pack of 2)
units
Alarm, Trickle Charger YY:MM:DD HH:MM:SS 96B Serial-SPI Through Hole PDIP 16 19.43 x 7.87 x 4.45mm 19.43mm 7.87mm 4.45mm 5.5 V +85 °C
RS Stock No. 169-8296
Mfr. Part No.ISL1208IB8Z
BrandIntersil
HK$17.223
Each (In a Tube of 100)
units
Alarm, Battery Backup, Calendar DW:DM:M:Y HH:MM:SS 2B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS Stock No. 189-7225
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. 189-8563
Mfr. Part No.DS12887+
HK$97.39
Each
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