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參數(shù)資料
| 型號： | MAX807_CWE |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Full-Featured レP Supervisory Circuit with 【1.5eset Accuracy |
| 中文描述： | 全功能レP監(jiān)控電路與精度【1.5eset |
| 文件頁數(shù)： | 14/16頁 |
| 文件大?。?/td> | 116K |
| 代理商： | MAX807_CWE |
M
BAT T OK Output
The BATT OK comparator monitors the backup battery
voltage, comparing it with a 2.265V reference (V
CC
≥
4V). BATT OK remains high as long as the backup bat-
tery voltage remains above 2.265V, signaling that the
backup battery has sufficient voltage to maintain the
memory of static RAM. When the battery voltage drops
below 2.265V, the BATT OK output drops low, signaling
that the backup battery needs to be changed.
__________Applic ations Information
The MAX807 is not short-circuit protected. Shorting
OUT to ground, other than power-up transients such as
charging a decoupling capacitor, may destroy the
device. If long leads connect to the IC’s inputs, ensure
that these lines are free from ringing and other condi-
tions that would forward bias the IC’s protection diodes.
There are two distinct modes of operation:
1) Normal Operating Mode, with all circuitry powered
up. Typical supply current from V
CC
is 70μA, while
only leakage currents flow from the battery.
2) Battery-Backup Mode, where V
CC
is below V
BATT
and V
RST
. The supply current from the battery is typ-
ically less than 1μA.
Using S uperCaps or
MaxCaps with the MAX 807
BATT has the same operating voltage range as V
CC
, and
the battery-switchover threshold voltage is typically
V
BATT
when V
CC
is decreasing or V
BATT
+ 0.06V when
V
CC
is increasing. This hysteresis allows use of a
SuperCap (e.g., order of 0.47F) and a simple charging
circuit as a backup source (Figure 13). Since V
BATT
can
exceed V
CC
while V
CC
is above the reset threshold,
there are no special precautions when using these μP
supervisors with a SuperCap.
Alternative Chip-Enable Gating
Using memory devices with CE and CE inputs allows
the MAX807 CE loop to be bypassed. To do this, con-
nect CE IN to ground, pull up CE OUT to OUT, and
connect CE OUT to the CE input of each memory
device (Figure 14). The CE input of each part then con-
nects directly to the chip-select logic, which does not
have to be gated by the MAX807.
Adding Hysteresis to the
Power-Fail Comparator
The power-fail comparator has a typical input hystere-
sis of 20mV. This is sufficient for most applications
where a power-supply line is being monitored through
an external voltage divider (Figure 10).
Figure 15 shows how to add hysteresis to the power-fail
comparator. Select the ratio of R1 and R2 such that PFI
sees 2.265V when V
IN
falls to the desired trip point
(V
TRIP
). Resistor R3 adds hysteresis. It will typically be
an order of magnitude greater than R1 or R2. The cur-
rent through R1 and R2 should be at least 1μA to
ensure that the 25nA (max) PFI input current does not
shift the trip point. R3 should be larger than 10k
to
prevent it from loading down the PFO pin. Capacitor C1
adds additional noise rejection.
Full-Featured μP S upervisory Circ uit with
±1.5% Reset Ac c urac y
14
______________________________________________________________________________________
Figure 13. SuperCap or MaxCap on BATT
MAX807
0.47F
1N4148
+5V
V
CC
GND
BATT
OUT
Figure 14. Alternate CE Gating
MAX807
OUT
GND
CE IN
CE
CE
CE OUT
CE
CE
CE
CE
CE
CE
*MAXIMUM Rp VALUE DEPENDS ON
THE NUMBER OF RAMS.
MINIMUM Rp VALUE IS 1k
ACTIVE-HIGH CE
LINES FROM LOGIC
RAM 1
RAM 2
RAM 3
RAM 4
Rp*
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX807_EPE | Full-Featured レP Supervisory Circuit with 【1.5eset Accuracy |
| MAX807_EWE | Full-Featured レP Supervisory Circuit with 【1.5eset Accuracy |
| MAX807_MJE | Full-Featured レP Supervisory Circuit with 【1.5eset Accuracy |
| MAX810SN293D2T1G | Rectifier Diodes; Mounting style: Surface mount; Package size: 2.9x1.6(t=1.0); Number of terminal: 5; Application: General Purpose Rectifier Diodes; Repetitive peak reverse voltage VRM(V): 400; Average rectified forward current IO(A): 0.5; |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX807L | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Full-Featured レP Supervisory Circuit with 【1.5eset Accuracy |
| MAX807LCPE | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX807LCPE+ | 功能描述:監(jiān)控電路 Full-Featured uPower Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX807LCUE | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX807LCUE+ | 功能描述:監(jiān)控電路 Full-Featured uPower Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
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