Document
M48T08 M48T08Y, M48T18
5 V, 64 Kbit (8 Kb x 8) TIMEKEEPER® SRAM
Features
■ Integrated ultra low power SRAM, real-time clock, power-fail control circuit, and battery
■ BYTEWIDE™ RAM-like clock access
■ BCD coded year, month, day, date, hours, minutes, and seconds
■ Typical clock accuracy of ±1 minute a month, at 25 °C
■ Automatic power-fail chip deselect and WRITE protection
■ WRITE protect VPFD = power-fail deselect voltage): – M48T08: VCC = 4.75 to 5.5 V; 4.5 V ≤ VPFD ≤ 4.75 V – M48T18/T08Y: VCC = 4.5 to 5.5 V; 4.2 V ≤ VPFD ≤ 4.5 V
■ Software controlled clock calibration for high accuracy applications
■ Self-contained battery and crystal in the CAPHAT™ DIP package
■ Packaging includes a 28-lead SOIC and SNAPHAT® top (to be ordered separately)
■ SOIC package provides direct connection for a snaphat top which contains the battery and crystal
■ Pin and function compatible with DS1643 and JEDEC standard 8 K x 8 SRAMs
■ RoHS compliant – Lead-free second level interconnect
28 1 PCDIP28 battery/crystal CAPHAT™
SNAPHAT® battery/crystal
28 1
SOH28
June 2011
Doc ID 2411 Rev 11
1/31
www.st.com
1
Contents
Contents
M48T08, M48T08Y, M48T18
1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Operation modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 READ mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2 WRITE mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.3 Data retention mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.4 Power-fail interrupt pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3 Clock operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.1 Reading the clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2 Setting the clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3 Stopping and starting the oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.4 Calibrating the clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.5 VCC noise and negative going transients . . . . . . . . . . . . . . . . . . . . . . . . . 18
4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5 DC and AC parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7 Part numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
8 Environmental information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
9 Revision history . ..