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| 型号： | MAX817LEPA+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 12/16页 |
| 文件大小： | 0K |
| 描述： | IC SUPERVISOR MPU 5V 8-DIP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| 类型： | 备用电池电路 |
| 监视电压数目： | 1 |
| 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： | 8-DIP（0.300"，7.62mm） |
| 供应商设备封装： | 8-PDIP |
| 包装： | 管件 |
+5V Microprocessor Supervisory Circuits
Backup-Battery Switchover
In a brownout or power failure, it may be necessary to
preserve the contents of RAM. With a backup battery
installed at BATT, the MAX817/MAX818/MAX819 auto-
matically switch RAM to backup power when V CC falls.
These devices require two conditions before switching
to battery-backup mode: 1) V CC must be below the
reset threshold, and 2) V CC must be below V BATT .
Table 1 lists the status of the inputs and outputs in bat-
tery-backup mode.
As long as V CC exceeds the reset threshold, OUT con-
nects to V CC through a 5 ? PMOS power switch. Once
V CC falls below the reset threshold, V CC or V BATT
(whichever is higher) switches to OUT. When V CC falls
below V RST and V BATT , BATT switches to OUT through
an 80 ? switch.
When V CC exceeds the reset threshold, it is connected to
the substrate, regardless of the voltage applied to BATT
(Figure 10). During this time, the diode (D1) between
BATT and the substrate will conduct current from BATT
to V CC if V BATT is 0.6V greater than V CC . When BATT
connects to OUT, backup mode is activated and the
internal circuitry is powered from the battery (Table 1).
When V CC is just below V BATT , the current draw from
BATT is typically 6μA. When V CC drops to more than 1V
below V BATT , the internal switchover comparator shuts
off and the supply current falls to less than 1μA.
__________Applications Information
The MAX817/MAX818/MAX819 are protected for typical
short-circuit conditions of 10sec or less. Shorting OUT
to ground for longer than 10sec destroys the device.
Decouple V CC , OUT, and BATT to ground by placing
0.1μF capacitors as close to the device as possible.
Table 1. Input and Output Status in
Battery-Backup Mode
SIGNAL
STATUS
V CC
V OUT
Disconnected from V OUT .
Connected to V BATT through an internal 80 ?
PMOS switch.
BATT
V CC
Connected to V OUT . Current drawn from
V BATT
the battery is less than 1μA, as long as
V CC < V BATT - 0.2V.
SW1
SW2
D1
D2
SW3
SW4
V R ESET
V WDI
Logic low
Watchdog timer is disabled.
SUBSTRATE
V C E OUT
V C E IN
Logic high. The open-circuit voltage is equal
to V OUT .
High impedance
MAX817
MAX818
MAX819
D3
OUT
V1
ADDITIONAL SUPPLY RESET VOLTAGE
V2
V CC
V2 (RESET) = 1.25
(
R1 + R 2
R2
)
CONDITION
SW1/SW2
SW3/SW4
V CC > Reset Threshold
Open
Closed
R1
R2
PFI
MAX819
RESET
MR
PFO
RESET
μ P
V CC < Reset Threshold and
V CC > V BATT
V CC < Reset Threshold and
V CC < V BATT
Open
Closed
Closed
Open
RESET THRESHOLD = 4.65V IN MAX81_L
RESET THRESHOLD = 4.4V IN MAX81_M
Figure 9. Monitoring an Additional Supply by Connecting
PFO to MR.
Figure 10. Backup-Battery-Switchover Block Diagram
12
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX817LEPA+ | 功能描述:监控电路 5V 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 |
| MAX817LESA | 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 |
| MAX817LESA+ | 功能描述:监控电路 5V 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 |
| MAX817LESA+T | 功能描述:监控电路 5V 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 |
| MAX817LESA-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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