Datasheet

Operating modes M48Z58, M48Z58Y
12/24 Doc ID 2559 Rev 11
2.4 V
CC
noise and negative going transients
I
CC
transients, including those produced by output switching, can produce voltage
fluctuations, resulting in spikes on the V
CC
bus. These transients can be reduced if
capacitors are used to store energy which stabilizes the V
CC
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 0.1 µF (see 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 negative voltage spikes on V
CC
that drive it to values below V
SS
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 V
CC
to V
SS
(cathode connected to V
CC
, anode to V
SS
). (Schottky diode 1N5817
is recommended for through hole and MBRS120T3 is recommended for surface mount).
Figure 8. Supply voltage protection
AI02169
V
CC
0.1µF DEVICE
V
CC
V
SS