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參數(shù)資料
| 型號(hào)： | MAX791 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Microprocessor Supervisory Circuit(微處理器監(jiān)控電路) |
| 中文描述： | 微處理器監(jiān)控電路 |
| 文件頁(yè)數(shù)： | 11/20頁(yè) |
| 文件大?。?/td> | 198K |
| 代理商： | MAX791 |
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Chip-Enable S ignal Gating
The MAX791 provides internal gating of chip-enable
(CE) signals, to prevent erroneous data from corrupting
the CMOS RAM in the event of a power failure. During
normal operation, the CE gate is enabled and passes
all CE transitions. When reset is asserted, this path
becomes disabled, preventing erroneous data from
corrupting the CMOS RAM. The MAX791 uses a series
transmission gate from the Chip-Enable Input (CE IN) to
CE OUT (Figure 1).
The 10ns max CE propagation from CE IN to CE OUT
enables the MAX791 to be used with most μPs.
Chip-Enable Input
CE IN is high impedance (disabled mode) while RESET
is asserted.
During a power-down sequence were V
CC
passes
4.65V, CE IN assumes a high-impedance state when
the voltage at CE IN goes high or 15μs after reset is
asserted, whichever occurs first (Figure 7).
During a power-up sequence, CE IN remains high
impedance, regardless of CE IN activity, until reset is
deasserted following the reset-timeout period.
In the high-impedance mode, the leakage currents into
this input are ±1μA max over temperature. In the low-
impedance mode, the impedance of CE IN appears as
a 75
resistor in series with the load at CE OUT.
The propagation delay through the CE transmission
gate depends on both the source impedance of the
drive to CE IN and the capacitive loading on CE OUT
(see the Chip-Enable Propagation Delay vs. CE OUT
Load Capacitance graph in the 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 50pF of load
capacitance (Figure 8). For minimum propagation
delay, minimize the capacitive load at CE OUT and use
a low output-impedance driver.
Chip-Enable Output
In the enabled mode, the impedance of CE OUT is
equivalent to 75
in series with the source driving CE
IN. In the disabled mode, the 75
transmission gate is
off and CE OUT is actively pulled to V
OUT
. This source
turns off when the transmission gate is enabled.
LOWLINE Output
The low-line comparator monitors V
CC
with a typical
threshold voltage 150mV above the reset threshold,
and has 15mV of hysteresis. LOWLINE typically sinks
3.2mA at 0.1V. For normal operation (V
CC
above the
LOWLINE threshold), LOWLINE is pulled to V
OUT
. If
access to the unregulated supply is unavailable, use
LOWLINE to provide a nonmaskable interrupt (NMI) to
the μP as V
CC
begins to fall (Figure 9a).
M
Mic roproc essor S upervisory Circ uit
______________________________________________________________________________________
11
V
CC
CE IN
RESET
THRESHOLD
CE OUT
RESET
RESET
100
μ
s
15
μ
s
100
μ
s
Figure 7. Reset and Chip-Enable Timing
MAX791
CE IN
C
LOAD
CE OUT
GND
+5V
50
DRIVER
V
CC
Figure 8. CE Propagation Delay Test Circuit
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX792R | Microprocessor and Non-Volatile Memory Supervisory Circuits(復(fù)位門(mén)限2.61V,微處理器和非易失存儲(chǔ)器監(jiān)控電路) |
| MAX792S | Microprocessor and Non-Volatile Memory Supervisory Circuits(復(fù)位門(mén)限1.91V,微處理器和非易失存儲(chǔ)器監(jiān)控電路) |
| MAX792T | Microprocessor and Non-Volatile Memory Supervisory Circuits(復(fù)位門(mén)限3.06V,微處理器和非易失存儲(chǔ)器監(jiān)控電路) |
| MAX793 | 3.0V/3.3V Adjustable Microprocessor Supervisory Circuits(具有監(jiān)控器、芯片使能和支持備用電池的復(fù)位器) |
| MAX794 | 3.0V/3.3V Adjustable Microprocessor Supervisory Circuits(具有可調(diào)閾值監(jiān)控器、芯片使能和支持備用電池的復(fù)位器) |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX791C/D | 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(lèi)型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開(kāi)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 |
| MAX791CPE | 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(lèi)型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開(kāi)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 |
| MAX791CPE+ | 功能描述:監(jiān)控電路 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(lèi)型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開(kāi)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 |
| MAX791CSE | 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(lèi)型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開(kāi)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 |
| MAX791CSE+ | 功能描述:監(jiān)控電路 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(lèi)型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開(kāi)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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