Comparison of the three supported RTC chips
ISL1220
DS3231
DS3232
RTC-8564
PCF8563
Year of datasheet
2006
2010
 2010
 ?
2010
Package
10 pin MSOP
SO16
 SO20
 VSOJ20
8 pin SO8 orDIP8 or HVSON10 or TSSOP8
Crystal
External
Internal
Internal
Internal
External
Temperature compensation
No
 Open loop - adjusts Xtal capacitance from temperature lookup table Open loop - adjusts Xtal capacitance from temperature lookup table
No ( but first device tested accurate to 6secs/year)
No
Frequency trimming?
I2C: Analogue Trimming Register (Hobcat controlled)
I2C: Aging register
(Hobcat controlled)
I2C: Aging register
(Hobcat controlled)
No
External 20pF trimmer
Cost (ukp-ex VAT)
1.37 ukp
9.97 ukp
 8.76 ukp
 3.48 ukp
1.88ukp
Alarm
(Not used in TrxAVR)
Resolution = seconds
span = 1 year
Two - resolution = minutes
span = 1 month
Two - resolution = minutes
span = 1 month
Resolution = minutes
span = 1 month
Resolution = minutes
span = 1 month
Clock output option
15 freqs:  1/32Hz to 32kHz
1, 4kHz, 8kHz, 32kHz
    
No
Vbat / Vdd switching
Built in switching
Built in switching
Built in switching
 Vdd pin only:
external diodes needed 		 Vdd pin only:
external diodes needed
Addition RAM bytes
(Not used in TrxAVR)
8 bytes
56 bytes
 236 bytes
 None
240 bytes
I2C address
hex 6F
hex 68
hex 68
hex 51
hex 51
Vbat curren
(3v coin cell)
400nA = 60yrs on CR2032
840nA = 30yrs on Cr2032
  1.5mA = 16yrs on CR2032  275nA = 80yrs on CR2032
(but ?1.5uA if Fout = 32kHz)
250nA = 80yrs on Cr2032
Home-brew PCB design
Yes - G3VPX
No
Yes G3VPX
No
No
Other
Vdd/Vbat changeover trimming register
Open-loop temperature compensation lookup every 64 seconds - this process is adjust by the I2C aging register (= trimming register)
  Open-loop temperature compensation lookup every 64 seconds - this process is adjust by the I2C aging register (= trimming register)  No trimming - has "frequency adjusted Xtal". A sample was tested accurate to 6sec/yr.

 

 

Back