M48Z129Y_10 Datasheet, PDF (11/20 Pages) STMicroelectronics – 5.0 V or 3.3 V, 1 Mbit (128 Kb x 8) ZEROPOWER® SRAM

M48Z129Y, M48Z129V
Operation modes
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 (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 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, it is recommended to connect 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
VCC
VCC
0.1µF
DEVICE
V_SS
AI02169
Doc ID 5716 Rev 7
11/20