SA25C020 Datasheet, PDF (27/31 Pages) List of Unclassifed Manufacturers – 2Mb EEPROM with 25MHz SPI Bus Interface

Powerup and Powerdown
The device must not be selected at
powerup or powerdown (that is, CSb must
follow the voltage applied on V_CC) until V_CC
reaches the correct value, as follows:
•= V_CC(min) at powerup, and then for a
further delay of t_PU (as described in
Table 10)
•= V_SS at powerdown
A simple pull-up resistor on CSb can
usually be used to insure safe and proper
powerup and powerdown. To avoid data
corruption and inadvertent write operations
during powerup, a Power On Reset (POR)
circuit is included. The logic inside the
device is held at reset while V_CC is less
than the POR threshold value (V_POR), all
operations are disabled and the device
does not respond to any instructions.
The device ignores all instructions until a
time delay of t_PU has elapsed after the
moment that V_CC rises above the VWI
threshold. However, correct operation of
the device is not guaranteed if by this time
V_CC is still below V_CC(min). No Write Status
Register, Program or Erase instructions
should be sent until t_PU reaches the
minimum V_CC threshold after V_CC.
SA25C020 Advanced Information
SAIFUN
27
At powerup, the device is in Standby mode
(not SP mode) and the WEN bit is reset.
Normal precautions must be taken for
supply rail decoupling to stabilize the V_CC
feed. Each device in a system should have
the V_CC rail decoupled by a suitable
capacitor close to the package pins (this
capacitor is generally of the order of
0.1 µF).
All operations are disabled and the device
does not respond to any instructions when
V_CC drops at powerdown from the
operating voltage to below the V_POR
threshold. (The designer must be aware
that if a powerdown occurs while a Write,
Program or Erase cycle is in progress, data
corruption can result.)
Table 10. Powerup
Symbol Parameter Min. Max. Unit
VPOR
POR Threshold
Value
2.2
2.4
V
tPU
VCC(min) to CS
low
2
ms