M48Z35 datasheet(13/20 Pages) STMICROELECTRONICS

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M48Z35, M48Z35Y

Table 10. Power Down/Up Trip Points DC Characteristics

Note: All voltages referenced to VSS.

1. Valid for Ambient Operating Temperature: TA = 0 to 70°C or –40 to 85°C; VCC = 4.75 to 5.5V or 4.5 to 5.5V (except where noted).

2. At 25°C.

VCC Noise And Negative Going Transients

ICC transients, including those produced by output

switching, can produce voltage fluctuations, re-

sulting inspikes onthe VCC bus. These transients

can be reduced if capacitors are used to store en-

ergy which stabilizes the VCC bus. The energy

stored in the bypass capacitors will be released as

low going spikes are generated or energy will be

absorbed when overshoots occur. A ceramic by-

pass capacitor value of 0.1µF (see Figure 12) is

recommended in order to provide the needed fil-

tering.

In addition to transients that are caused by normal

SRAM operation, power cycling can generate neg-

ative voltage spikes on VCC that drive it to values

below VSS by as much as one volt. These negative

spikes can cause data corruption in the SRAM

while in battery backup mode. To protect from

these voltage spikes, ST recommends connecting

a schottky diode from VCC to VSS (cathode con-

nected to VCC, anode to VSS). (Schottky diode

1N5817 is recommended for through hole and

MBRS120T3 is recommended for surface mount).

Figure 12. Supply Voltage Protection

Symbol

Parameter(1)

Min

Typ

Max

Unit

VPFD

Power-fail Deselect Voltage

M48Z35

4.5

4.6

4.75

M48Z35Y

4.2

4.35

4.5

VSO

Battery Back-up Switchover Voltage

M48Z35/Y

3.0

tDR

(2)

Expected Data Retention Time

YEARS

AI02169

VCC

0.1

µF

DEVICE

VCC

VSS

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