AT25128B/AT25256B
Electrical Characteristics
4.5
SPI Synchronous Data Timimg
tCS
VIH
CS
VIL
tCSS
tCSH
VIH
tWH
tWL
SCK
VIL
tSU
tH
VIH
VIL
SI
Valid Data In
tHO
tDIS
tV
VOH
High
High
SO
Impedance
Impedance
VOL
4.6
Electrical Specifications
4.6.1
Power-Up Requirements and Reset Behavior
During a power-up sequence, the VCC supplied to the AT25128B/AT25256B should monotonically rise
from GND to the minimum VCC level, as specified in Table 4-1, with a slew rate no faster than 0.1 V/µs.
4.6.1.1 Device Reset
To prevent inadvertent write operations or any other spurious events from occurring during a power-up
sequence, the AT25128B/AT25256B includes a Power-on Reset (POR) circuit. Upon power-up, the
device will not respond to any instructions until the VCC level crosses the internal voltage threshold (VPOR
that brings the device out of Reset and into Standby mode.
)
The system designer must ensure the instructions are not sent to the device until the VCC supply has
reached a stable value greater than or equal to the minimum VCC level. Additionally, once the VCC is
greater than or equal to the minimum VCC level, the bus master must wait at least tPUP before sending the
first instruction to the device. See Table 4-4 for the values associated with these power-up parameters.
Table 4-4.ꢀPower-Up Conditions(1)
Symbol
Parameter
Min. Max. Units
tPUP
Time required after VCC is stable before the device can accept instructions 100
－
1.5
－
µs
V
VPOR Power-on Reset Threshold Voltage
－
tPOFF Minimum time at VCC = 0V between power cycles
0.03
ms
Note:ꢀ
1. These parameters are characterized but they are not 100% tested in production.
If an event occurs in the system where the VCC level supplied to the AT25128B/AT25256B drops below
the maximum VPOR level specified, it is recommended that a full-power cycle sequence be performed by
first driving the VCC pin to GND in less than 1 ms, waiting at least the minimum tPOFF time and then
performing a new power-up sequence in compliance with the requirements defined in this section.
DS20006193A-page 13
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