DS1556 Datasheet, PDF (16/20 Pages) Dallas Semiconductor – 1M, Nonvolatile, Y2K-Compliant Timekeeping RAM

DS1556 1M, Nonvolatile, Y2K-Compliant Timekeeping RAM
AC TEST CONDITIONS
Output Load: 50 pF + 1TTL Gate
Input Pulse Levels:
0.0 to 3.0V
Timing Measurement Reference Levels:
Input: 1.5V
Output: 1.5V
Input Pulse Rise and Fall Times: 5 ns
NOTES:
1. Voltage referenced to ground.
2. Typical values are at +25°C and nominal supplies.
3. Outputs are open.
4. Battery switchover occurs at the lower of either the battery voltage or V_PF.
5. The IRQ/FT and RST outputs are open drain.
6. Data-retention time is at +25°C.
7. Each DS1556 has a built-in switch that disconnects the lithium source until V_CC is first applied by the
user. The expected t_DR is defined for DIP modules and PowerCap modules as a cumulative time in the
absence of V_CC starting from the time power is first applied by the user.
8. RTC modules (DIP) can be successfully processed through conventional wave-soldering techniques
as long as temperature exposure to the lithium energy source contained within does not exceed
+85°C. Post-solder cleaning with water-washing techniques is acceptable, provided that ultrasonic
vibration is not used.
In addition, for the PowerCap:
a. Dallas Semiconductor recommends that PowerCap Module bases experience one pass through
solder reflow oriented with the label side up (“live-bug”).
b. Hand soldering and touch-up: Do not touch or apply the soldering iron to leads for more than
3 seconds. To solder, apply flux to the pad, heat the lead frame pad and apply solder. To remove
the part, apply flux, heat the lead frame pad until the solder reflow and use a solder wick to
remove solder.
9. t_AH1, t_DH1 are measured from WE going high.
10. t_AH2, t_DH2 are measured from CE going high.
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