View ds1904 datasheet:

PRELIMINARY DS1904 RTC iButton www.iButton.com SPECIAL FEATURES Presence detector acknowledges when reader Real-Time Clock/calendar in binary format first applies voltage Uses the same binary time/date representation Meets UL#913 (4th Edit.); Intrinsically Safe as the DS1994 but with 1 second resolution Apparatus, Approved under Entity Concept Clock accuracy is better than ± 2 minutes per for use in Class I, Division 1, Group A, B, C month at 25°C and D Locations (application pending) Operating temperature range from -40°C to +70°C ? Over 10 years of operation F5 MicroCan? ? ? 5.89 COMMON iButton FEATURES 0.36 0.51 Unique, factory–lasered and tested 64-bit registration number (8-bit family code + 48- 16.25 bit serial number + 8-bit CRC tester) assures Y