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參數(shù)資料
| 型號(hào)： | MAX818MESA |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 電源管理 |
| 英文描述： | +5V Microprocessor Supervisory Circuits |
| 中文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
| 封裝： | 0.150 INCH, SOIC-8 |
| 文件頁(yè)數(shù)： | 11/16頁(yè) |
| 文件大小： | 114K |
| 代理商： | MAX818MESA |
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M
+5V Mic roproc essor S upervisory Circ uits
______________________________________________________________________________________
11
Any time a reset is generated, the CE transmission gate
remains disabled and
CE
IN remains high impedance
(regardless of
CE
IN activity) for the reset timeout peri-
od. When the CE transmission gate is enabled, the
impedance of
CE
IN appears as a 40
resistor in series
with the load at
CE
OUT. The propagation delay
through the CE transmission gate depends on V
CC
, the
source impedance of the drive connected to
CE
IN,
and the loading on
CE
OUT (see Typical Operating
Characteristics). The CE propagation delay is produc-
tion tested from the 50% point on
CE
IN to the 50%
point on
CE
OUT using a 50
driver and a 50pF load
capacitance (Figure 7). For minimum propagation
delay, minimize the capacitive load at
CE
OUT and use
a low-output-impedance driver.
Chip-Enable Output (MAX 818)
When the CE transmission gate is enabled, the imped-
ance of
CE
OUT is equivalent to a 40
resistor in series
with the source driving
CE
IN. In the disabled mode,
the transmission gate is off and an active pull-up con-
nects
CE
OUT to OUT (Figure 5). This pull-up turns off
when the transmission gate is enabled.
Power-Fail Comparator
(MAX 817/MAX 819)
The MAX817/MAX819 PFI input is compared to an inter-
nal reference. If PFI is less than the power-fail threshold
(V
PFT
),
PFO
goes low. The power-fail comparator is
intended for use as an undervoltage detector to signal a
failing power supply (Figure 8). However, the comparator
does not need to be dedicated to this function because it
is completely separate from the rest of the circuitry.
The power-fail comparator turns off and
PFO
goes low
when V
CC
falls below V
BATT
. During the reset timeout
period (t
RP
),
PFO
is forced high, regardless of the state
of V
PFI
(see Battery Freshness Sealsection). If the com-
parator is unused, connect PFI to ground and leave
PFO
unconnected.
PFO
can be connected to
MR
on the
MAX819 so that a low voltage on PFI will generate a
reset (Figure 9). In this configuration, when the monitored
voltage causes PFI to fall below V
PFT
,
PFO
pulls
MR
low,
causing a reset to be asserted. Reset remains asserted
as long as
PFO
holds
MR
low, and for t
RP
(200ms) after
PFO
pulls
MR
high when the monitored supply is above
the programmed threshold. When
PFO
is connected to
MR
, it is not possible to enable the battery freshness
seal. Enabling the battery freshness seal requires
MR
to
be high or open. Once the battery freshness seal is
enabled, it is no longer affected by
PFO
’s connection to
MR
.
Figure 7. CE Propagation Delay Test Circuit
CE IN
BATT
CE OUT
GND
MAX818
C
L
*
* C
L
INCLUDES LOAD CAPACITANCE, STRAY CAPACITANCE,
AND SCOPE-PROBE CAPACITANCE.
50pF
V
CC
+5V
50
50
Figure 8. Using the Power-Fail Comparator to Generate a
Power-Fail Warning
MAX817
MAX819
V
WARN
= 1.25
POWER-FAIL-WARNING TRIP VOLTAGE
R1 + R2
( )
PFI
PFO
R1
R2
μ
P
V
CC
V
IN
NMI
RESET
1.25V
RESET
+5V
REGULATOR
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX818MESA+ | 功能描述:監(jiān)控電路 5V MPU Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)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 |
| MAX818MESA+T | 功能描述:監(jiān)控電路 5V MPU Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)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 |
| MAX818MESA-T | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)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 |
| MAX819_CPA | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:+5V Microprocessor Supervisory Circuits |
| MAX819_CSA | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:+5V Microprocessor Supervisory Circuits |
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