M48Z128 datasheet(13/21 Pages) STMICROELECTRONICS

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M48Z128, M48Z128Y, M48Z128V*

Data Retention Mode

With valid VCC applied, the M48Z128/Y/V oper-

ates as a conventional BYTEWIDE™ static RAM.

Should the supply voltage decay, the RAM will au-

tomatically power-fail deselect, write protecting it-

self tWP after VCC falls below VPFD. All outputs

become high impedance, and all inputs are treated

as “Don't care.”

If power fail detection occurs during a valid ac-

cess, the memory cycle continues to completion. If

the memory cycle fails to terminate within the time

tWP, write protection takes place. When VCC drops

below VSO, the control circuit switches power to

the internal energy source which preserves data.

The internal coin cell will maintain data in the

M48Z128/Y/V after the initial application of VCC for

an accumulated period of at least 10 years when

VCC is less than VSO. As system power returns

and VCC rises above VSO, the battery is discon-

nected, and the power supply is switched to exter-

nal VCC. Write protection continues for tER after

VCC reaches VPFD to allow for processor stabiliza-

tion. After tER, normal RAM operation can resume.

For more information on Battery Storage Life refer

to the Application Note AN1012.

Figure 11. Power Down/Up Mode AC Waveforms

Table 10. Power Down/Up AC Characteristics

Note: 1. Valid for Ambient Operating Temperature: TA = 0 to 70°C; VCC = 4.75 to 5.5V, 4.5 to 5.5V, or 3.0 to 3.6V (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 pass-

es VPFD (min).

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

Symbol

Parameter(1)

Min

Max

Unit

(2)

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

300

µs

tFB

(3)

VPFD (min) to VSS VCC Fall Time

M48Z128/Y

µs

M48Z128V

150

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

µs

tRB

VSS to VPFD (min) VCC Rise Time

1µs

tWP

Write Protect Time

M48Z128/Y

150

µs

M48Z128V

250

tER

E Recovery Time

120

AI01031

VCC

(PER CONTROL INPUT)

OUTPUTS

DON'T CARE

HIGH-Z

tFB

tRB

tWP

tDR

VALID

(PER CONTROL INPUT)

RECOGNIZED

VPFD (max)

VPFD (min)

VSO

tER

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