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. 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. 921-5721
Mfr. Part No.ISL12020MIRZ
HK$55.61
Each (In a Pack of 2)
units
Alarm, Battery Backup, Calendar, Switch Over DW:DM:M:Y HH:MM:SS 128B Serial-I2C Surface Mount DFN 20 5.5 x 4 x 1.3mm 5.5mm 4mm 1.3mm 5.5 V +85 °C
RS Stock No. 189-8609
Mfr. Part No.DS12887A+
HK$90.84
Each
units
Alarm, Calendar Binary, DW:DM:M:Y Binary, HH:MM:SS 114B Multiplexed Through Hole EDIP 24 34.04 x 18.29 x 9.4mm 34.04mm 18.29mm 9.4mm 5.5 V +70 °C
RS Stock No. 920-9001
Mfr. Part No.M48T35Y-70PC1
HK$234.436
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. 786-0751
Mfr. Part No.DS1338Z-3+
HK$32.435
Each (In a Pack of 2)
units
Clock M:M:DW SS:MM:HH 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. 667-6224
Mfr. Part No.Q42724231000711
BrandEPSON
HK$59.42
Each
units
Calendar DW:DM:M:Y HH:MM:SS - Parallel 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. 192-1246
Mfr. Part No.DS1744W-120+
HK$216.558
Each (In a Tube of 12)
units
Calendar YY:MM:DD HH:MM:SS 32 x 8B Parallel Through Hole EDIP 28 39.37 x 18.8 x 10.67mm 39.37mm 18.8mm 10.67mm 0.6 V, 3.6 V +70 °C
RS Stock No. 190-5166
Mfr. Part No.DS3232SN#T&R
HK$81.67
Each
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. 196-9066
Mfr. Part No.ISL12057IUZ
HK$18.69
Each (In a Tube of 50)
units
- DW:DM:M:Y HH:MM:SS - - - MSOP 8 - - - - - -
RS Stock No. 189-8685
Mfr. Part No.DS1339C-33#
HK$53.50
Each (In a Pack of 2)
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. 166-1602
Mfr. Part No.PCF8563TS/4,118
BrandNXP
HK$10.193
Each (On a Reel of 2500)
units
Alarm, Battery Backup, Calendar, Watchdog Timer DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount TSSOP 8 3.1 x 3.1 x 0.95mm 3.1mm 3.1mm 0.95mm 5.5 V +85 °C
RS Stock No. 191-3233
Mfr. Part No.DS1308U-33+
HK$29.915
Each (In a Tube of 50)
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. 190-5835
Mfr. Part No.DS1339C-33#T&R
HK$54.535
Each (In a Pack of 2)
units
Alarm, Clock, Real Time Clock, Square Wave Output, Trickle Charger 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 +85 °C
RS Stock No. 191-3700
Mfr. Part No.DS1374U-33+T&R
HK$28.892
Each (In a Pack of 5)
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 5.5 V +85 °C
RS Stock No. 880-5349
Mfr. Part No.M41T94MQ6F
HK$31.198
Each (In a Pack of 5)
units
Alarm, Battery Backup, Interrupt, NVRAM, Real Time Clock, Watchdog Timer Binary, D:D:M:Y:C Binary, HH:MM:SS 44B Serial-SPI Surface Mount SOIC 16 10 x 4 x 1.6mm 10mm 4mm 1.6mm 5.5 V +85 °C
RS Stock No. 190-4748
Mfr. Part No.DS1744-70IND+
HK$317.113
Each (In a Tube of 12)
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
RS Stock No. 923-7778
Mfr. Part No.DS1747-70+
HK$323.379
Each (In a Tube of 10)
units
Calendar YY:MM:DD HH:MM:SS 512 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. 190-4743
Mfr. Part No.DS1670E+
HK$68.567
Each (In a Tube of 74)
units
Real Time Clock, SRAM DM:M:DW:Y SS:MM:HH - Multiplexed Surface Mount TSSOP 20 6.6 x 4.5 x 0.95mm 6.6mm 4.5mm 0.95mm 3.63 V +70 °C
RS Stock No. 192-1238
Mfr. Part No.DS1556-70+
HK$314.295
Each (In a Tube of 11)
units
Alarm, NV SRAM, Watchdog Timer, Y2K YY:MM:DD HH:MM:SS - 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. 192-1626
Mfr. Part No.DS1248Y-70+
HK$297.92
Each
units
SRAM with Phantom Clock YY:MM:DD HH:MM:SS:hh 128 x 8bit Serial Through Hole EDIP 32 44.2 x 18.8 x 10.92mm 44.2mm 18.8mm 10.92mm 5 V +70 °C