Manual

DS1249Y/AB
021497 7/9
POWER–DOWN/POWER–UP TIMING (t
A
: See Note 10)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
V
CC
Fail Detect to CE and WE
Inactive
t
PD
1.5 µs 11
V
CC
Slew from V
TP
to 0V t
F
150 µs
V
CC
Slew from 0V to V
TP
t
R
150 µs
V
CC
Valid to CE and WE Inactive t
PU
2 ms
V
CC
Valid to End of Write
Protection
t
REC
125 ms
(t
A
= 25°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Expected Data Retention Time t
DR
10 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 throughout 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 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 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 V
CC
is first applied by the user. 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.
10.All AC and DC electrical characteristics are valid over the full operating temperature range. For commercial prod-
ucts, 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
, t
DH1
are measured from WE going high.
13.t
WR2
, t
DH2
are measured from CE going high.