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參數(shù)資料
| 型號： | ASM805LMJA |
| 廠商： | ALLIANCE SEMICONDUCTOR CORP |
| 元件分類： | 電源管理 |
| 英文描述： | UP Power Supply Supervisor With Battery Backup Switch |
| 中文描述： | 2-CHANNEL POWER SUPPLY MANAGEMENT CKT, CDIP8 |
| 封裝： | CERAMIC, DIP-8 |
| 文件頁數(shù)： | 5/13頁 |
| 文件大?。?/td> | 323K |
| 代理商： | ASM805LMJA |
5 of 13
Notice: The information in this document is subject to change without notice
ASM690A / 692A
ASM802L / 802M
ASM805L
μP Power Supply Supervisor With Battery Backup Switch
rev 1.0
October 2003
Backup Power Sources - Batteries
Battery voltage selection is important to insure that the
battery does not discharge through the parasitic device diode
D1 (see
Figure 3
) when V
CC
is less than V
BATT
and V
CC
>
V
RT
.
Table 2: Maximum Battery Voltages
Although most batteries that meet the requirements of
Table
2
are acceptable, lithium batteries are very effective backup
source due to their high-energy density and very low self-
discharge rates.
Battery replacement while Powered
Batteries can be replaced even when the device is in a
powered state as long as V
CC
remains above the reset
threshold voltage V
RT
. In the ASM devices, a floating V
BATT
pin will not cause a powersupply switchover as can occur in
some other supervisory circuits. If V
BATT
is not used, the pin
should be grounded.
Backup Power Sources - SuperCap
Capacitor storage, with very high values of capacitance, can
be used as a back-up power source instead of batteries.
SuperCap
are capacitors with capacities in the fractional
farad range. A 0.1 farad SuperCap would provide a useful
backup power source. Like the battery supply, it is important
that the capacitor voltage remain below the maximum
voltages shown in
Table 2
. Although the circuit of
Figure 4
shows the most simple way to connect the SuperCap, this
circuit cannot insure that an over voltage condition will not
occur since the capacitor will ultimately charge up to V
CC
. To
insure that an over voltage condition does not occur, the
circuit of
Figure 5
is preferred. In this circuit configuration, the
diode-resistor pair clamps the capacitor voltage at one diode
drop below V
CC
. V
CC
itself should be regulated within ±5% of
5V for the ASM692A/802M or within ±10% of 5V for the
ASM690A/802L/805L to insure that the storage capacitor
does not achieve an over voltage state.
Note: SuperCap
TM
is a trademark of Baknor Industries
Part Number
MAXIMUM Battery Voltage
ASM690A
4.80
ASM802L
4.80
ASM805L
4.80
ASM692A
4.55
ASM802M
4.55
100K
ASM692A
ASM802M
V
CC
V
OUT
V
BATT
RESET
(RESET)
GND
To μP
+
0.1F
Figure 5: Capacitor as a backup power source
Voltage clamped to 0.5V below V
CC
V
CC
V
OUT
V
BATT
RESET
(RESET)
GND
To μP
+5V
0.1F
+
Figure 4: Capacitor as a backup power source
D2
D1
To
SRAM
D1
ASM692A
ASM802M
To
SRAM
+5V
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| ASM690ACSA | UP Power Supply Supervisor With Battery Backup Switch |
| ASM690AEPA | UP Power Supply Supervisor With Battery Backup Switch |
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