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| 型号： | MAX807NCWE+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 15/16页 |
| 文件大小： | 0K |
| 描述： | IC SUPERVISOR MPU 16-SOIC |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 46 |
| 类型： | 备用电池电路 |
| 监视电压数目： | 1 |
| 复位： | 高有效/低有效 |
| 复位超时： | 最小为 140 ms |
| 电压 - 阀值： | 4.425V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SOIC（0.295"，7.50mm 宽） |
| 供应商设备封装： | 16-SOIC W |
| 包装： | 管件 |
Full-Featured μP Supervisory Circuit with
±1.5% Reset Accuracy
Backup-Battery Replacement
The backup battery may be disconnected while V CC is
above the reset threshold, provided BATT is bypassed
with a 0.1μF capacitor to ground. No precautions are
necessary to avoid spurious reset pulses.
Negative-Going V CC Transients
While issuing resets to the μP during power-up, power-
down, and brownout conditions, these supervisors are
relatively immune to short-duration negative-going V CC
transients (glitches). It is usually undesirable to reset
the μP when V CC experiences only small glitches.
The Typical Operating Characteristics show Maximum
Transient Duration vs. Reset Comparator Overdrive, for
which reset pulses are not generated. The graph was
produced using negative-going V CC pulses, starting at
5V and ending below the reset threshold by the magni-
tude indicated (reset comparator overdrive). The graph
shows the maximum pulse width that a negative-going
V CC transient may typically have without causing a
reset pulse to be issued. As the amplitude of the tran-
sient increases (i.e., goes farther below the reset
threshold), the maximum allowable pulse width
decreases.
Typically, a V CC transient that goes 40mV below the
reset threshold and lasts for 3μs or less will not cause a
reset pulse to be issued.
START
SET
WDI
LOW
SUBROUTINE
OR PROGRAM LOOP,
SET WDI
HIGH
RETURN
END
Figure 16. Watchdog Flow Diagram
A 0.1μF bypass capacitor mounted close to the V CC
pin provides additional transient immunity.
Watchdog Software Considerations
To help the watchdog timer keep a closer watch on soft-
ware execution, you can use the method of setting and
resetting the watchdog input at different points in the
R1
VIN
PFI
+5V
V CC
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 16 shows an example flow diagram where the
R2
R3
C1*
MAX807
I/O driving the watchdog input is set high at the begin-
ning of the program, set low at the beginning of every
subroutine or loop, then set high again when the pro-
gram returns to the beginning. If the program should
PFO
GND
“hang” in any subroutine, the I/O is continually set low
and the watchdog timer is allowed to time out, causing
+5V
PFO
0V
TO μ P
*OPTIONAL
a reset or interrupt to be issued.
Maximum V CC Fall Time
The V CC fall time is limited by the propagation delay of
the battery switchover comparator and should not
exceed 0.03V/μs. A standard rule for filter capacitance
0V
V TRIP = 2.265
V H = 2.265 /
R1 + R2
R2
R2 || R3
R1 + R2 || R3
V L V TRIP V H
V IN
V L - 2.265 + 5 - 2.265 = 2.265
R1 R3 R2
on most regulators is on the order of 100μF per amp of
current. When the power supply is shut off or the main
battery is disconnected, the associated initial V CC fall
rate is just the inverse or 1A / 100μF = 0.01V/μs. The
V CC fall rate decreases with time as V CC falls exponen-
tially, which more than satisfies the maximum fall-time
Figure 15. Adding Hysteresis to the Power-Fail Comparator
requirement.
______________________________________________________________________________________
15
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX807NCWE+ | 功能描述:监控电路 Full-Featured uPower 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 |
| MAX807NCWE+T | 功能描述:监控电路 Full-Featured uPower 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 |
| MAX807NCWE-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 |
| MAX807NEPE | 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 |
| MAX807NEPE+ | 功能描述:监控电路 Full-Featured uPower 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 |
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