M95640-W M95640-R M95640-DF
Operating features
5
Operating features
5.1
Supply voltage (VCC)
5.1.1
Operating supply voltage V
CC
Prior to selecting the memory and issuing instructions to it, a valid and stable V voltage
CC
within the specified [V (min), V (max)] range must be applied (see Operating conditions
CC
CC
in Section 9: DC and AC parameters). This voltage must remain stable and valid until the
end of the transmission of the instruction and, for a Write instruction, until the completion of
the internal write cycle (t ). In order to secure a stable DC supply voltage, it is
W
recommended to decouple the V line with a suitable capacitor (usually of the order of
CC
10 nF to 100 nF) close to the V /V device pins.
CC SS
5.1.2
Device reset
In order to prevent erroneous instruction decoding and inadvertent Write operations during
power-up, a power-on-reset (POR) circuit is included. At power-up, the device does not
respond to any instruction until VCC reaches the POR threshold voltage. This threshold is
lower than the minimum V operating voltage (see Operating conditions in Section 9: DC
CC
and AC parameters).
At power-up, when V passes over the POR threshold, the device is reset and is in the
CC
following state:
●
●
●
in Standby Power mode,
deselected,
Status Register values:
–
–
–
The Write Enable Latch (WEL) bit is reset to 0.
The Write In Progress (WIP) bit is reset to 0.
The SRWD, BP1 and BP0 bits remain unchanged (non-volatile bits).
It is important to note that the device must not be accessed until V reaches a valid and
CC
stable level within the specified [V (min), V (max)] range, as defined under Operating
CC
CC
conditions in Section 9: DC and AC parameters.
5.1.3
Power-up conditions
When the power supply is turned on, V rises continuously from V to V . During this
CC
SS
CC
time, the Chip Select (S) line is not allowed to float but should follow the V voltage. It is
CC
therefore recommended to connect the S line to V via a suitable pull-up resistor (see
CC
Figure 4).
In addition, the Chip Select (S) input offers a built-in safety feature, as the S input is edge-
sensitive as well as level-sensitive: after power-up, the device does not become selected
until a falling edge has first been detected on Chip Select (S). This ensures that Chip Select
(S) must have been high, prior to going low to start the first operation.
The V voltage has to rise continuously from 0 V up to the minimum V operating voltage
CC
CC
defined under Operating conditions in Section 9: DC and AC parameters, and the rise time
must not vary faster than 1 V/µs.
Doc ID 16877 Rev 16
13/47
STMICROELECTRONICS [ ST ]
