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参数资料
| 型号： | MAX791EPE+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 14/19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
cally ±30mV centered at VBATT, allowing use of a
SuperCap and a simple charging circuit as a backup
source (Figure 12).
+5V
If V CC is above the reset threshold and VBATT is 0.5V
1N4148
3
V CC
above V CC , current flows to V OUT and V CC from VBATT
until the voltage at VBATT is less than 0.5V above V CC .
For example, with a SuperCap connected to VBATT
and through a diode to V CC , if V CC quickly changes
0.47F
1
VBATT
MAX791
V OUT
2
from 5.4V to 4.9V, the capacitor discharges through
V OUT and V CC until VBATT reaches 5.3V typ. Leakage
current through the SuperCap charging diode and
MAX791 internal power diode eventually discharges the
SuperCap to V CC . Also, if V CC and VBATT start from
0.5V above the reset threshold and power is lost at
GND
4
Figure 12. SuperCap or MaxCap on VBATT
Applications Information
The MAX791 is not short-circuit protected. Shorting
V OUT to ground, other than power-up transients such
as charging a decoupling capacitor, destroys the
device.
All open-circuit outputs swing between V OUT and GND
rather than V CC and GND.
If long leads connect to the chip inputs, ensure that
these lines are free from ringing and other conditions
that would forward bias the chip’s protection diodes.
There are three distinct modes of operation:
1) Normal operating mode with all circuitry powered
up. Typical supply current from V CC is 60μA, while
only leakage currents flow from the battery.
2) Battery-backup mode where V CC is typically within
0.7V below VBATT. All circuitry is powered up and
the supply current from the battery is typically less
than 60μA.
3) Battery-backup mode where V CC is less than
VBATT by at least 0.7V. VBATT supply current is
less than 1μA max.
Using SuperCaps or MaxCaps
with the MAX791
VBATT has the same operating voltage range as V CC ,
and the battery-switchover threshold voltages are typi-
V CC , the SuperCap on VBATT discharges through V CC
until VBATT reaches the reset threshold; the MAX791
then switches to battery-backup mode and the current
through V CC goes to zero (Figure 10).
Using Separate Power Supplies
for VBATT and V CC
If using separate power supplies for V CC and VBATT,
VBATT must be less than 0.3V above V CC when V CC is
above the reset threshold. As described in the previous
section, if VBATT exceeds this limit and power is lost at
V CC , current flows continuously from VBATT to V CC via
the VBATT-to-V OUT diode and the V OUT -to-V CC switch
until the circuit is broken (Figure 10).
Alternative Chip-Enable Gating
Using memory devices with CE and CE inputs allows
the MAX791 CE loop to be bypassed. To do this, con-
nect CE IN to ground, pull up CE OUT to V OUT , and
connect CE OUT to the CE input of each memory
device (Figure 13). The CE input of each part then con-
nects directly to the chip-select logic, which does not
have to be gated by the MAX791.
Adding Hysteresis to the
Power-Fail Comparator
Hysteresis adds a noise margin to the power-fail com-
parator and prevents repeated triggering of PFO when
VIN is near the power-fail comparator trip point. Figure
14 shows how to add hysteresis to the power-fail com-
parator. Select the ratio of R1 and R2 so that PFI sees
1.25V when VIN falls to the desired trip point (V TRIP ).
Resistor R3 adds hysteresis. It will typically be an order
of magnitude greater than R1 or R2. The current
through R1 and R2 should be at least 1μA to ensure
that the 25nA (max) PFI input current does not shift the
trip point. R3 should be larger than 10k ? to prevent it
from loading down the PFO pin. Capacitor C1 adds
additional noise rejection.
14
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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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