參數(shù)資料
型號: M48T129Y-70CS1
廠商: STMICROELECTRONICS
元件分類: 時鐘/數(shù)據(jù)恢復(fù)及定時提取
英文描述: 0 TIMER(S), REAL TIME CLOCK, PDSO44
封裝: PLASTIC, SO-44
文件頁數(shù): 14/30頁
文件大小: 162K
代理商: M48T129Y-70CS1
21/30
M48T129Y, M48T129V
Power-on Reset
The M48T129Y/V continuously monitors VCC.
When VCC falls to the power fail detect trip point,
the RST pulls low (open drain) and remains low on
power-up for tREC after VCC passes VPFD (max).
The RST pin is an open drain output and an appro-
priate pull-up resistor to VCC should be chosen to
control the rise time.
Battery Low Warning
The M48T129Y/V automatically performs battery
voltage monitoring upon power-up and at factory-
programmed time intervals of approximately 24
hours. The Battery Low (BL) Bit, Bit D4 of Flags
Register 1FFF0h, will be asserted if the battery
voltage is found to be less than approximately
2.5V.
If a battery low is generated during a power-up se-
quence, this indicates that the battery is below ap-
proximately 2.5 volts and may not be able to
maintain data integrity in the SRAM. Data should
be considered suspect and verified as correct.
If a battery low indication is generated during the
24-hour interval check, this indicates that the bat-
tery is near end of life. However, data is not com-
promised due to the fact that a nominal VCC is
supplied.
The M48T129Y/V only monitors the battery when
a nominal VCC is applied to the device. Thus appli-
cations which require extensive durations in the
battery back-up mode should be powered-up peri-
odically (at least once every few months) in order
for this technique to be beneficial. Additionally, if a
battery low is indicated, data integrity should be
verified upon power-up via a checksum or other
technique.
Initial 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 and FT.
Figure 15. Crystal Accuracy Across Temperature
AI00999
–160
0
1020304050
6070
Frequency (ppm)
Temperature
°C
80
–10
–20
–30
–40
–100
–120
–140
–40
–60
–80
20
0
–20
F
= -0.038
(T - T
0)
2 ± 10%
F
ppm
C
2
T
0 =25 °C
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