
23
Power-Down/Power-Up Timing—bq4285L (TA = TOPR)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
Conditions
tF
VCC slew from 2.7V to 0V
300
-
s
tR
VCC slew from 0V to 2.7V
100
-
s
tCSR
CS at VIH after power-up
20
-
200
ms
Internal write-protection
period after VCC passes VPFD
on power-up.
tWPT
Write-protect time for ex-
ternal RAM
-0
-
VBC > VPFD
10
16
30
sVBC < VPFD
tCER
Chip enable recovery time
tCSR
-
tCSR
ms
Time during which external
SRAM is write-protected after
VCC passes VPFD on power-up.
tCED
Chip enable propagation
delay to external SRAM
-
9
15
ns
Caution:
Negative undershoots below the absolute maximum rating of -0.3V in battery-backup mode
may affect data integrity.
Power-Down/Power-Up Timing—bq4285L
bq4285E/L