M95640-DF datasheet(13/53 Pages) STMICROELECTRONICS

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M95640-W M95640-R M95640-DF

Operating features

5.1

Supply voltage (VCC)

5.1.1

Operating supply voltage (VCC)

Prior to selecting the memory and issuing instructions to it, a valid and stable VCC voltage

within the specified [VCC(min), VCC(max)] range must be applied (see Operating conditions

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 (tW). In order to secure a stable DC supply voltage, it is

recommended to decouple the VCC line with a suitable capacitor (usually of the order of

10 nF to 100 nF) close to the VCC/VSS device pins.

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 VCC operating voltage (see Operating conditions in Section 9).

At power-up, when VCC passes over the POR threshold, the device is reset and is in the

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 VCC reaches a valid and

stable level within the specified [VCC(min), VCC(max)] range, as defined under Operating

conditions in Section 9.

5.1.3

Power-up conditions

When the power supply is turned on, VCC rises continuously from VSS to VCC. During this

time, the Chip Select (S) line is not allowed to float but should follow the VCC voltage. It is

therefore recommended to connect the S line to VCC via a suitable pull-up resistor (see

Figure 5).

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 VCC voltage has to rise continuously from 0 V up to the minimum VCC operating voltage

defined under Operating conditions in Section 9.

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