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| 型号： | DS1238-10N+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 7/14页 |
| 文件大小： | 0K |
| 描述： | IC MICROMANAGER 10% 16-DIP |
| 标准包装： | 25 |
| 系列： | MicroManager |
| 类型： | 备用电池电路 |
| 监视电压数目： | 1 |
| 输出： | 开路漏极，推挽式 |
| 复位： | 高有效/低有效 |
| 复位超时： | 最小为 40 ms |
| 电压 - 阀值： | 4.37V |
| 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 |
DS1238
MEMORY BACKUP
The DS1238 provides all of the necessary functions required to battery back a static RAM. First, an
internal switch is provided to supply SRAM power from the primary 5-volt supply (V CC ) or from an
external battery (V BAT ), whichever is greater. Second, the s am e power-fail detection described in the
power monitor section is used to hold the chip enable output ( CEO ) to within 0.3 volts of V CC or to within
0.7 volts of V BAT . The output voltage diode drop from V BAT (0.7 V) is necessary to prevent charging of
the battery in violation of UL standards. Write protection occurs as V CC falls below V CCTP as specified. If
CEI is low at the time power-fail detection occurs, CEO is held in its present state until CEI is returned
high, or the period t CE expires. This delay of write protection until the current memory cycle is completed
prevents the corruption of data. If CEO is in an inactive state at the time of V CC fail detection, CEO will
be unconditionally disabled within t CF . During nominal supply conditions CEO will follow CEI with a
maximum propagation delay of 20 ns. Figure 7 shows a typical nonvolatile SRAM application.
FRESHNESS SEAL
In order to conserve battery capacity during storage and/or shipment of an end system, the DS1238
provides an internal freshness seal to electrically disconnect the battery. Figure 8 depicts the three pulses
below ground on the IN pin required to invoke the freshness seal. The freshness seal will result in the tri-
state of outputs V CCO , RST, RST , and CEO . The WDS output will be driven active low. The PF pin is not
disabled by the freshness mode and will continue to source power from the V BAT pin whenever V CC is
below V BAT . The freshness seal will be disconnected and normal operation will begin when V CC is cycled
and reapplied to a level above V BAT .
To prevent negative pulses associated with noise from setting the freshness mode in system applications,
a series diode and resistor can be used to shunt noise to ground. During manufacturing, the freshness seal
can still be set by holding TP2 at -3 volts while applying the 0 to -3-volt clock to TP1.
POWER SWITCHING
When larger operating currents are required in a battery-backed system, the internal switching devices of
the DS1238 may be too small to support the required load through V CCO with a reasonable voltage drop.
For these applications, the PF output is provided to gate external power switching devices. As shown in
Figure 9, power to the load is switched from V CC to battery on power-down, and from battery to V CC on
power-p. The DS1336 is designed to use the PF output to switch between V BAT and V CC . It provides
better leakage and switchover performance than currently available discrete components. The transition
threshold for PF is set to the external battery voltage V BAT , allowing a smooth transition between sources.
Any load applied to the PF pin by an external switch will be supplied by the battery. Therefore, if a
discrete switch is used, this load should be taken into consideration when sizing the battery.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DS1238-10N+ | 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 |
| DS1238-5 | 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 |
| DS1238-5+ | 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 |
| DS1238A | 制造商:DALLAS 制造商全称:Dallas Semiconductor 功能描述:MicroManager |
| DS1238A-10 | 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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