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参数资料
| 型号： | MAX791EPE+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 9/19页 |
| 文件大小： | 0K |
| 描述： | IC SUPERVISOR MPU 16-DIP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 25 |
| 类型： | 备用电池电路 |
| 监视电压数目： | 1 |
| 输出： | 推挽式，图腾柱 |
| 复位： | 低有效 |
| 复位超时： | 最小为 140 ms |
| 电压 - 阀值： | 4.65V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 通孔 |
| 封装/外壳： | 16-DIP（0.300"，7.62mm） |
| 供应商设备封装： | 16-PDIP |
| 包装： | 管件 |
Microprocessor Supervisory Circuit
high or low for longer than the watchdog timeout period
(1.6s nominal), WDPO and WDO are asserted, indicat-
RESET
MAX791
15
10k
TO μ P RESET
ing a software fault condition (see Watchdog Output
and Watchdog-Pulse Output sections).
Watchdog Input
A change of state (high to low, low to high, or a mini-
mum 100ns pulse) at WDI during the watchdog period
resets the watchdog timer. The watchdog default time-
out is 1.6s. Select alternative timeout periods by con-
necting an external capacitor from SWT to GND (see
– — — — — –
Figure 4. Adding an External Pull-Down Resistor Ensures
R E S E T is Valid with V CC Down to GND
RESET Output
The MAX791’s RESET output ensures that the μP pow-
ers up in a known state, and prevents code-execution
errors during power-down or brownout conditions.
The RESET output is active low, and typically sinks
3.2mA at 0.1V saturation voltage in its active state.
When deasserted, RESET sources 1.6mA at typically
V OUT - 0.5V. When no backup battery is used, RESET
output is guaranteed to be valid down to V CC = 1V, and
an external 10k ? pull-down resistor on RESET ensures
that RESET will be valid with V CC down to GND (Figure
4). As V CC goes below 1V, the gate drive to the RESET
output switch reduces accordingly, increasing the
r DS(ON) and the saturation voltage. The 10k ? pull-down
resistor ensures the parallel combination of switch plus
resistor is around 10k ? and the output saturation volt-
age is below 0.4V while sinking 40μA. When using a
10k ? external pull-down resistor, the high state for the
RESET output with V CC = 4.75V is 4.5V typ. For battery
voltages ≥ 2V connected to VBATT, RESET remains
valid for V CC from 0V to 5.5V.
RESET will be asserted during the following conditions:
? V CC < 4.65V (typ).
Selecting an Alternative Watchdog Timeout Period sec-
tion).
To disable the watchdog function, leave WDI floating.
An internal resistor network (100k ? equivalent imped-
ance at WDI) biases WDI to approximately 1.6V.
Internal comparators detect this level and disable the
watchdog timer. When V CC is below the reset thresh-
old, the watchdog function is disabled and WDI is dis-
connected from its internal resistor network, thus
becoming high impedance.
Watchdog Output
WDO remains high if there is a transition or pulse at
WDI during the watchdog-timeout period. The watch-
dog function is disabled and WDO is a logic high when
V CC is below the reset threshold, battery-backup mode
is enabled, or WDI is an open circuit. In watchdog
mode, if no transition occurs at WDI during the watch-
dog-timeout period, WDO goes low 70ns after the
falling edge of WDPO and remains low until the next
transition at WDI (Figure 5). A flip-flop can force the
system into a hardware shutdown if there are two suc-
cessive watchdog faults (Figure 6). WDO has a 2 x TTL
output characteristic.
?
?
MR < 1.25V (typ).
RESET remains asserted for 200ms (typ) after V CC
rises above 4.65V or after MR has exceeded
WDI
1.6s
100ns MIN
1.25V.
The MAX791 battery-switchover comparator does not
affect RESET assertion. However, RESET is asserted in
battery-backup mode since V CC must be below the
reset threshold to enter this mode.
Watchdog Function
The watchdog monitors μP activity via the Watchdog
Input (WDI). If the μP becomes inactive, WDO and
WDPO are asserted. To use the watchdog function,
connect WDI to a bus line or μP I/O line. If WDI remains
WDPO
70ns
WDO
– — — – – — — — –
Figure 5. WDI, W D O , and W D P O Timing Diagram (V CC Mode)
_______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX791EPE+ | 功能描述:监控电路 MPU Supervisor RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel |
| MAX791ESE | 功能描述:监控电路 RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel |
| MAX791ESE+ | 功能描述:监控电路 MPU Supervisor RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel |
| MAX791ESE+T | 功能描述:监控电路 MPU Supervisor RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel |
| MAX791ESE-T | 功能描述:监控电路 RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel |
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