M25PE80 datasheet(44/61 Pages) STMICROELECTRONICS

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Power-up and Power-down

M25PE80

44/61

Power-up and Power-down

At Power-up and Power-down, the device must not be selected (that is Chip Select (S) must

follow the voltage applied on VCC) until VCC reaches the correct value:

●

VCC(min) at Power-up, and then for a further delay of tVSL

●

VSS at Power-down

Usually a simple pull-up resistor on Chip Select (S) can be used to ensure safe and proper

Power-up and Power-down.

To avoid data corruption and inadvertent write operations during power-up, a Power On

Reset (POR) circuit is included. The logic inside the device is held reset while VCC is less

than the Power On Reset (POR) threshold voltage, VWI – all operations are disabled, and

the device does not respond to any instruction.

Moreover, the device ignores all Write Enable (WREN), Page Write (PW), Page Program

(PP), Page Erase (PE), Sector Erase (SE), Bulk Erase (BE) and Write to Lock Register

(WRLR) instructions until a time delay of tPUW has elapsed after the moment that VCC rises

above the VWI threshold. However, the correct operation of the device is not guaranteed if,

by this time, VCC is still below VCC(min). No Write, Program or Erase instructions should be

sent until the later of:

●

tPUW after VCC passed the VWI threshold

●

tVSL after VCC passed the VCC(min) level

These values are specified in Table 14.

If the delay, tVSL, has elapsed, after VCC has risen above VCC(min), the device can be

selected for READ instructions even if the tPUW delay is not yet fully elapsed.

As an extra protection, the Reset (Reset) signal could be driven Low for the whole duration

of the Power-up and Power-down phases.

At Power-up, the device is in the following state:

●

The device is in the Standby mode (not the Deep Power-down mode).

●

The Write Enable Latch (WEL) bit is reset.

Normal precautions must be taken for supply rail decoupling, to stabilize the VCC supply.

Each device in a system should have the VCC rail decoupled by a suitable capacitor close to

the package pins. (Generally, this capacitor is of the order of 0.1µF).

At Power-down, when VCC drops from the operating voltage, to below the Power On Reset

(POR) threshold voltage, VWI, all operations are disabled and the device does not respond

to any instruction. (The designer needs to be aware that if a Power-down occurs while a

Write, Program or Erase cycle is in progress, some data corruption can result.)

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