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參數(shù)資料
| 型號(hào)： | SP704 |
| 英文描述： | Low Power Microprocessor Supervisory with Battery Switch-Over |
| 中文描述： | 低功耗微處理器監(jiān)控與電池開關(guān)過(guò) |
| 文件頁(yè)數(shù)： | 10/16頁(yè) |
| 文件大小： | 216K |
| 代理商： | SP704 |
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SP703/704DS/07
SP703/704 Low Power Microprocessor Supervisory
10
Copyright 2000 Sipex Corporation
Power-Fail Comparator
The Power-Fail Comparator can be used as an
under-voltage detector to signal the failing of a
power supply (it is completely separate from the
rest of the circuitry and does not need to be
dedicated to this function). The PFI input is
compared to an internal 1.25V reference. If PFI
is less than 1.25V, PFO goes low. The external
voltage divider drives PFI to sense the unregu-
lated DC input to the +5V regulator. The volt-
age-divider ratio can be chosen such that the
voltage at PFI falls below 1.25V just before the
+5V regulator drops out. PFO then triggers an
interrupt which signals the
μ
P to prepare for
power-down.
When V
connects to V
, the power-fail
comparator is turned off and PFO is forced low
to conserve backup-battery power.
Backup-Battery Switchover
In the event of a brownout or power failure, it
may be necessary to preserve the contents of
RAM. With a backup battery installed at V
,
the RAM is assured to have power if V
fails.
As long as V
exceeds the reset threshold,
V
connects to V
through a 0.6
PMOS
power switch. Once V
CC
falls below the reset
threshold, V
or V
, whichever is higher,
switches to V
. V
connects to V
through a 5
switch only when V
is below the
reset threshold and V
BATT
is greater than V
CC
.
When V
exceeds the reset threshold, it is
connected to V
OUT
, regardless of the voltage
applied to V
Figure 9
. During this time,
the diode (D1) between V
BATT
and V
OUT
will
conduct current from V
BATT
OUT
if V
BATT
is
more than .6V above V
OUT
.
When V
connects to V
, backup mode is
activated and the internal circuitry will be
powered from the battery
Figure 10
. When V
is just below V
, in the backup mode the
current drawn from V
will be typically
30
μ
A. When V
drops to more than 1V below
V
, the internal switchover comparator shuts
off and the supply current falls to less than 0.6
μ
A.
Reset Threshold = 4.65V in SP703
Reset Threshold = 4.40V in SP704
Figure 9. BACKUP-BATTERY Switchover Block Diagram
SW1
D1
D2
D3
SW2
V
BATT
V
CC
GND
V
OUT
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PDF描述 |
|---|---|
| SP704CN | Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP704CP | Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP704EN | Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP704EP | Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP706S | +3.0V/+3.3V Low Power Microprocessor Supervisory Circuits |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP7041-HAR | 制造商:Methode Electronics Inc 功能描述: |
| SP7041-JN | 制造商:Methode Electronics Inc 功能描述: |
| SP7044 | 制造商:Semi Circuits 功能描述: |
| SP704CN | 制造商:Exar Corporation 功能描述: |
| SP704CP | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Power Microprocessor Supervisory with Battery Switch-Over |
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