M48Z02, M48Z12
VCC Noise And Negative Going Transients
ICC transients, including those produced by output
switching, can produce voltage fluctuations, re-
sulting in spikes on the 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
12) is recommended in order to provide the need-
ed 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 12. Supply Voltage Protection
VCC
0.1µF
VCC
DEVICE
VSS
AI02169
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