m4t28-br12sh6tr STMicroelectronics, m4t28-br12sh6tr Datasheet - Page 13

• Manufacturer Part Number: m4t28-br12sh6tr
• Description: 64 Kbit 8kb X8 Timekeeper Sram With Address/data Multiplexed
• Manufacturer: STMicroelectronics

Figure 12. Reset Timing Waveforms
Table 12. Reset AC Characteristics (T
BATTERY LOW WARNING
The M48T559Y checks its battery voltage on pow-
er-up. The BL (Battery Low) bit (D4 of 1FF0h) will
be set on power-up if the battery voltage is less
than 2.5V (typical).
POWER-ON DEFAULTS
Upon application of power to the device, the fol-
lowing register bits are set to a ’0’ state: WDS;
BMB0-BMB4; RB0-RB1; AFE; ABE; W; R; FT.
POWER SUPPLY DECOUPLING
and UNDERSHOOT PROTECTION
I
switching, can produce voltage fluctuations, re-
sulting in spikes on the V
can be reduced if capacitors are used to store en-
ergy, which stabilizes the V
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
14) 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-
CC
Symbol
transients, including those produced by output
t
t
R1HRZ
R2HRZ
t
t
R1
R2
RSTIN1
RSTIN2
RST
RSTIN1 Low to RST Low
RSTIN2 Low to RST Low
RSTIN1 High to RST Hi-Z
RSTIN2 High to RST Hi-Z
CC
bus. These transients
CC
tR1
bus. The energy
Parameter
A
= 0 to 70° C; V
tR1HRZ
ative voltage spikes on V
below V
tive spikes can cause data corruption in the SRAM
while in battery backup mode. To protect from
these voltage spikes, it is recommended to con-
nect a schottky diode from V
connected to V
1N5817 is recommended for through hole and
MBRS120T3 is recommended for surface mount.
Figure 13. Supply Voltage Protection
Hi-Z
tR2
CC
= 4.5V to 5.5V)
V CC
SS
by as much as one Volt. These nega-
0.1 F
CC
, anode to V
Min
50
20
40
40
tR2HRZ
CC
Hi-Z
AI01679
that drive it to values
CC
SS
V CC
V SS
). Schottky diode
Max
200
100
200
200
to V
DEVICE
M48T559Y
SS
AI02169
(cathode
Unit
ms
ms
ms
ns
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