DS1249Y Datasheet, PDF (7/8 Pages) Dallas Semiconductor – 2048k Nonvolatile SRAM

POWER-DOWN/POWER-UP TIMING
PARAMETER
SYMBOL
V_CC Fail Detect to CE and WE Inactive
t_PD
V_CC slew from V_TP to 0V
t_F
V_CC slew from 0V to V_TP
t_R
V_CC Valid to CE and WE Inactive
t_PU
V_CC Valid to End of Write Protection
t_REC
MIN
150
150
TYP
DS1249Y/AB
(t_A: See Note 10)
MAX UNITS NOTES
1.5
µs
11
µs
µs
2
ms
125
ms
PARAMETER
Expected Data Retention Time
SYMBOL MIN TYP
t_DR
10
MAX
(t_A=25°C)
UNITS NOTES
years
9
WARNING:
Under no circumstance are negative undershoots, of any amplitude, allowed when device is in battery
backup mode.
NOTES:
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_DS is measured from the earlier of CE or WE going high.
5. These parameters are sampled with a 5 pF load and are not 100% tested.
6. If the CE low transition occurs simultaneously with or latter 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 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. Each DS1249 has a built-in switch that disconnects the lithium source until the user first applies V_CC.
The expected t_DR is defined as accumulative time in the absence of V_CC starting from the time power
is first applied by the user. This parameter is assured by component selection, process control, and
design. It is not measured directly during production testing.
10. All AC and DC electrical characteristics are valid over the full operating temperature range. For
commercial products, this range is 0°C to 70°C. For industrial products (IND), this range is -40°C to
+85°C.
11. In a power-down condition the voltage on any pin may not exceed the voltage on V_CC.
12. t_WR1 and t_DH1 are measured from WE going high.
13. t_WR2 and t_DH2 are measured from CE going high.
14. DS1249 modules are recognized by Underwriters Laboratory (U.L.) under file E99151.
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