DS1251 Datasheet, PDF (18/22 Pages) Dallas Semiconductor – 4096k NV SRAM with Phantom Clock

AC TEST CONDITIONS
Output Load:
50pF + 1TTL Gate
Input Pulse Levels: 0V to 3V
NOTES:
DS1251/DS1251P
Timing Measurement Reference Levels
Input:
1.5V
Output:
1.5V
Input Pulse Rise and Fall Times: 5ns
1) WE is high for a read cycle.
2) OE = V_IH or V_IL. If OE = V_IH during write cycle, the output buffers remain in a high impedance
state.
3) t_WP is specified as the logical AND of CE and WE . t_WP is measured from the latter of CE or WE
going low to the earlier of CE or WE going high.
4) t_DH, t _DS are measured from the earlier of CE or WE going high.
5) These parameters are sampled with a 50pF load and are not 100% tested.
6) If the CE low transition occurs simultaneously with or later than the WE low transition in Write
Cycle 1, the output buffers remain in a high impedance state during this period.
7) If the CE high transition occurs prior to or simultaneously with the WE high transition, the output
buffers remain in a high impedance state during this period.
8) If WE is low or the WE low transition occurs prior to or simultaneously with the CE low transition,
the output buffers remain in a high impedance state during this period.
9) The expected t_DR is defined as cumulative time in the absence of V_CC with the clock oscillator
running.
10) t_WR is a function of the latter occurring edge of WE or CE .
11) Voltages are referenced to ground.
12) RST (Pin 1) has an internal pullup resistor.
13) Real-time clock modules 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:
1) Dallas Semiconductor recommends that PowerCap Module bases experience one pass through solder
reflow oriented with the label side up (“live-bug”).
2) Hand soldering and touch-up: Do not touch or apply the soldering iron to leads for more than three
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 reflows, and use a solder wick to remove
solder.
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