M41ST84W datasheet(14/31 Pages) STMICROELECTRONICS

14 / 31 page

M41ST84Y, M41ST84W

14/31

Data Retention Mode

With valid VCC applied, the M41ST84Y/W can be

accessed as described above with READ or

WRITE cycles. Should the supply voltage decay,

the M41ST84Y/W will automatically deselect,

write protecting itself when VCC falls between

VPFD(max) and VPFD(min). This is accomplished

by internally inhibiting access to the clock regis-

ters. At this time, the Reset pin (RST) is driven ac-

tive and will remain active until VCC returns to

nominal levels. When VCC falls below the Battery

Back-up Switchover Voltage (VSO), power input is

switched from the VCC pin to the SNAPHAT

® (or

external) battery, and the clock registers and

SRAM are maintained from the attached battery

supply.

All outputs become high impedance. On power up,

when VCC returns to a nominal value, write protec-

tion continues for tREC. The RST signal also re-

mains active during this time (see Figure 16, page

14).

For a further more detailed review of lifetime calcu-

lations, please see Application Note AN1012.

Figure 16. Power Down/Up Mode AC Waveforms

Table 8. Power Down/Up AC Characteristics

Note: 1. Valid for Ambient Operating Temperature: TA = –40 to 85°C; VCC = 2.7 to 3.6V or 4.5 to 5.5V (except where noted).

2. VPFD(max) to VPFD(min) fall time of less than tF may result in deselection/write protection not occurring until 200µs after VCC passes

VPFD(min).

3. VPFD(min) to VSS fall time of less than tFB may cause corruption of RAM data.

4. Programmable (see Table 13, page 23)

5. At 25°C (when using SOH28 + M4T28-BR12SH SNAPHAT top); VCC = 0V.

Symbol

Parameter(1)

Min

Typ

Max

Unit

(2)

VPFD(max) to VPFD(min) VCC Fall Time

300

µs

tFB

(3)

VPFD(min) to VSS VCC Fall Time

µs

tPFD

PFI to PFO Propagation Delay

µs

VPFD(min) to VPFD(max) VCC Rise Time

µs

tRB

VSS to VPFD(min) VCC Rise Time

1µs

tREC(4)

Power up Deselect Time

200

tDR

(5)

Expected Data Retention Time

YEARS

AI03681

VCC

INPUTS

(PER CONTROL INPUT)

OUTPUTS

DON'T CARE

HIGH-Z

tFB

tRB

tDR

VALID

(PER CONTROL INPUT)

RECOGNIZED

VPFD (max)

VPFD (min)

VSO

tREC

RST

PFO

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