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參數資料
| 型號： | MAX814TC |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | 【1% Accuracy, Low-Power, +3V and +5V レP Supervisory Circuits |
| 中文描述： | 【1％精度，低功耗，3V和5VレP監(jiān)控電路 |
| 文件頁數： | 13/16頁 |
| 文件大?。?/td> | 111K |
| 代理商： | MAX814TC |
Monitoring V oltages Other than V
CC
Monitor voltages other than the V
CC
by connecting a
voltage divider to PFI and adjusting the ratio appropri-
ately. If required, add hysteresis by connecting a resis-
tor (with a value approximately 10-times the sum of the
two resistors in the potential divider network) between
PFI and PFO. A capacitor between PFI and GND will
reduce the power-fail circuit’s sensitivity to high-fre-
quency noise on the line being monitored. RESET can
be asserted on other voltages in addition to the +5V
V
CC
line. Connect PFO to MR to initiate a reset when
PFI drops below 2.50V (K, L, N suffix) or 1.70V (T suffix
or MAX816). Figure 11 shows the MAX814K/L/N/
MAX815K/L/N configured to assert RESET when the
+5V supply falls below the reset threshold, or when the
+12V supply falls below approximately 11V.
Monitoring a Negative V oltage
The power-fail comparator can also monitor a negative
supply rail (Figure 12). When the negative rail is good
(a negative voltage of large magnitude), PFO is low.
When the negative rail is degraded (a negative voltage
of lesser magnitude), PFO is high. By adding the resis-
tors and transistor as shown, a high PFO triggers reset.
As long as PFO remains high, the MAX814/MAX815/
MAX816 will keep reset asserted (RESET = low, RESET
= high). Note that this circuit’s accuracy depends on the
PFI threshold tolerance, the V
CC
line, and the resistor.
Watc hdog S oftware Considerations
A way to help the watchdog timer keep closer tabs on
software execution involves setting and resetting the
watchdog input at different points in the program,
rather than pulsing the watchdog input high-low-high or
low-high-low. This technique avoids a stuck loop where
the watchdog timer continues to be reset within the
loop, keeping the watchdog from timing out. Figure 13
shows an example flow diagram where the I/O driving
the watchdog input is set low at the beginning of the
program, set high at the beginning of every subroutine,
then set low at the end of every subroutine. If the pro-
gram should hang in any subroutine, the I/O is continu-
ally set high and the watchdog timer is allowed to time
out, causing a reset to be issued.
M
±1% Ac c urac y, Low-Power, +3V and +5V
μP S upervisory Circ uits
______________________________________________________________________________________
13
MAX814
MAX815
MAX816
RESET
R1
MAX814K/L/N
MAX815K/L/N
RESET
100k
1%
PARAMETER
MIN
TYP
MAX
UNIT
+12V Reset
Threshold at +25°C
10.57 11.00 11.45
V
340k
1%
+5V
+12V
V
CC
PFI
GND
MR
PFO
TO
μ
P
Figure 10. RESET Valid to Ground Circuit
Figure 11. Monitoring Both +5V and +12V
相關PDF資料 |
PDF描述 |
|---|---|
| MAX814TE | 【1% Accuracy, Low-Power, +3V and +5V レP Supervisory Circuits |
| MAX815 | 【1% Accuracy, Low-Power, +3V and +5V レP Supervisory Circuits |
| MAX815C | 【1% Accuracy, Low-Power, +3V and +5V レP Supervisory Circuits |
| MAX815CPA | 【1% Accuracy, Low-Power, +3V and +5V レP Supervisory Circuits |
| MAX815CSA | 【1% Accuracy, Low-Power, +3V and +5V レP Supervisory Circuits |
相關代理商/技術參數 |
參數描述 |
|---|---|
| MAX814TCPA | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數: 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復位:Resettable 監(jiān)視器:No Watchdog 電池備用開關:No Backup 上電復位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX814TCPA+ | 功能描述:監(jiān)控電路 3V & 5V uPower Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數: 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復位:Resettable 監(jiān)視器:No Watchdog 電池備用開關:No Backup 上電復位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX814TCSA | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數: 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復位:Resettable 監(jiān)視器:No Watchdog 電池備用開關:No Backup 上電復位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX814TCSA+ | 功能描述:監(jiān)控電路 3V & 5V uPower Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數: 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復位:Resettable 監(jiān)視器:No Watchdog 電池備用開關:No Backup 上電復位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX814TCSA+T | 功能描述:監(jiān)控電路 3V & 5V uPower Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數: 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復位:Resettable 監(jiān)視器:No Watchdog 電池備用開關:No Backup 上電復位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
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