- 您现在的位置：买卖IC网 > PDF目录381717 > DS1238 (DALLAS SEMICONDUCTOR) MicroManager(微管理器芯片) PDF资料下载
参数资料
| 型号： | DS1238 |
| 厂商： | DALLAS SEMICONDUCTOR |
| 元件分类： | 电源管理 |
| 英文描述： | MicroManager(微管理器芯片) |
| 中文描述： | 1-CHANNEL POWER SUPPLY MANAGEMENT CKT, PDIP16 |
| 封装： | 0.300 INCH, DIP-16 |
| 文件页数： | 7/13页 |
| 文件大小： | 167K |
| 代理商： | DS1238 |
DS1238
022698 7/13
MEMORY BACKUP
The DS1238 provides all of the necessary functions re-
quired to battery back a static RAM. First, an internal
switch is provided to supply SRAM power from the pri-
mary 5-volt supply (V
CC
) or from an external battery
(V
BAT
), whichever is greater. Second, the same 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 volt-
age diode drop from V
BAT
(0.7 V) is necessary to pre-
vent 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 re-
turned 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 un-
conditionally disabled within t
CF
. During nominal supply
conditions CEO will follow CEI with a maximum propa-
gation delay of 20 ns. Figure 7 shows a typical nonvola-
tile SRAM application.
FRESHNESS SEAL
In order to conserve battery capacity during storage
and/or shipment of an end system, the DS1238 pro-
vides an internal freshness seal to electrically discon-
nect 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 out-
puts 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 fresh-
ness 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 se-
ries 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 bat-
tery-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 ex-
ternal 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 up. The
DS1336 is designed to use the PF output to switch be-
tween V
BAT
and V
CC
. It provides better leakage and
switchover performance than currently available dis-
crete 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.
NONVOLATILE SRAM
Figure 7
GND
RST
SRAM
To uP
+3V
From
Decoder
DS1238
+5 V
DC
V
BAT
V
CCO
V
CC
CEI
CEO
RST
CE
V
CC
相关PDF资料 |
PDF描述 |
|---|---|
| DS1239 | MicroManager Chip(微管理器芯片) |
| DS1250AB | 4096K Nonvolatile SRAM(4096K 非易失性静态RAM) |
| DS1250Y | 4096K Nonvolatile SRAM(4096K 非易失性静态RAM) |
| DS1250W | 3.3V 4096K Nonvolatile SRAM(3.3V 4096K 非易失性静态RAM) |
| DS1251Y | 4096K NV SRAM with Phantom Clock(带幻影时钟的4096K NV 静态RAM) |
相关代理商/技术参数 |
参数描述 |
|---|---|
| DS1238-10 | 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 |
| DS1238-10+ | 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 |
| 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 |
| DS1238-10N+ | 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 |
发布紧急采购，3分钟左右您将得到回复。