M48T512Y Datasheet, PDF (13/21 Pages) STMicroelectronics – 3.3V-5V 4 Mbit 512Kb x8 TIMEKEEPER SRAM

Figure 9. Calibration Waveform
M48T512Y, M48T512V*
NORMAL
POSITIVE
CALIBRATION
NEGATIVE
CALIBRATION
AI00594B
V_CC Noise And Negative Going Transients
I_CC transients, including those produced by output
switching, can produce voltage fluctuations, re-
sulting in spikes on the V_CC bus. These transients
can be reduced if capacitors are used to store en-
ergy, 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 0.1µF is rec-
ommended 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 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 con-
nected to V_CC, anode to V_SS). (Schottky diode
1N5817 is recommended for through hole and
MBRS120T3 is recommended for surface mount).
Figure 10. Supply Voltage Protection
VCC
0.1µF
VCC
DEVICE
VSS
AI02169
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