M40Z111MH6 datasheet(9/15 Pages) STMICROELECTRONICS

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M40Z111, M40Z111W

Table 6. Power Down/Up AC Characteristics

Note: 1. Valid for Ambient Operating Temperature: TA = –40 to 85°C; VCC = 4.5 to 5.5V or 2.7 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 200 µs after VCC

passes VPFD (min).

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

4. tER (min) = 20ms for Industrial Temperature Range - Grade 6 device.

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 (as shown in Figure

8) is recommended in order to provide the needed

filtering.

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, STMicroelectronics recom-

mends connecting a schottky diode from VCC to

VSS (cathode connected to VCC, anode to VSS).

Schottky diode 1N5817 is recommended for

through hole and MBRS120T3 is recommended

for surface mount.

Figure 8. Supply Voltage Protection

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

µs

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

µs

tRB

VSS to VPFD (min) VCC Rise Time

1µs

tEDL

Chip Enable Propagation Delay

M40Z111

M40Z111W

tEDH

Chip Enable Propagation Delay

M40Z111

M40Z111W

tER

(4)

Chip Enable Recovery

200

tWPT

Write Protect Time

M40Z111

150

µs

M40Z111W

250

µs

AI00622

VCC

0.1

µF

DEVICE

VCC

VSS

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