M40Z111W datasheet(10/21 Pages) STMICROELECTRONICS

10 / 21 page

Operation

M40Z111, M40Z111W

10/21

Table 2.

Power down/up AC characteristics

2.2

VCC noise and negative going transients

ICC transients, including those produced by output switching, can produce voltage

fluctuations, resulting in spikes on the VCC bus. These transients can be reduced if

capacitors are used to store energy 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 bypass capacitor value of 0.1µF (as shown in

Figure 6) is recommended in order to provide the needed filtering.

In addition to transients that are caused by normal SRAM operation, power cycling can

generate negative 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 recommends

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.

Symbol

Parameter(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).

Min

Max

Unit

(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).

VPFD (max) to VPFD (min) VCC fall time

300

µs

tFB

(3)

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

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

µs

tEDL

Chip enable propagation delay

M40Z111

M40Z111W

tEDH

Chip enable propagation delay

M40Z111

M40Z111W

tER

(4)

tER (min) = 20ms for industrial temperature range - grade 6 device.

Chip enable recovery

200

tWPT

Write protect time

M40Z111

150

µs

M40Z111W

250

µs

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