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參數(shù)資料
| 型號： | ASM802M |
| 廠商： | Alliance Semiconductor Corporation |
| 英文描述： | UP Power Supply Supervisor With Battery Backup Switch |
| 中文描述： | 電源的監(jiān)控帶備用電池開關 |
| 文件頁數(shù)： | 4/13頁 |
| 文件大?。?/td> | 323K |
| 代理商： | ASM802M |
4 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
Watchdog Input
As discussed in the Reset section, the Watchdog input is
used to monitor microprocessor activity. It can be used to
insure that the microprocessor is in a continually responsive
state by requiring that the WDI pin be toggled every second.
If the WDI pin is not toggled within the 1.6 second window
(minimum t
WD
+ t
RS
), a reset pulse will be asserted to return
the microprocessor to the initial start-up state. Pulses as
short as 50ns can be applied to the WDI pin. If this feature is
not used, the WDI pin should be open circuited or the logic
placed into a high-impedance state to allow the pin to float.
Backup-Battery Switchover
A power loss can be made less severe if the system RAM
contents are preserved. This is achieved in the ASM690/692/
802/805 by switching from the failed V
CC
to an alternate
power source connected at V
BATT
when V
CC
is less than the
reset threshold voltage (V
CC
< V
RT
), and V
CC
is less than
V
BATT
. The V
OUT
pin is normally connected to V
CC
through a
2
PMOS switch but a brown-out or loss of V
CC
will cause a
switchover to V
BATT
by means of a 20
PMOS switch.
Although both conditions (V
CC
< V
RT
and V
CC
<V
BATT
) must
occur for the switchover to V
BATT
to occur, V
OUT
will be
switched back to V
CC
when V
CC
exceeds V
RT
irrespective of
the voltage at V
BATT
. It should be noted that an internal
device diode (D1 in
Figure 3
) will be forward biased if V
BATT
exceeds V
CC
by more than a diode drop when V
CC
is
switched to V
OUT
. Because of this it is recommended that
V
BATT
be no greater than V
RT
+0.6V.
Table 1. Pin Connections in Battery Backup Mode
During the backup power mode, the internal circuitry of the
supervisory circuit draws power from the battery supply.
While V
CC
is still alive, the comparator circuits remain alive
and the current drawn by the device is typically 35μA. When
V
CC
drops more than 1.1V below V
BATT
, the internal
switchover comparator, the PFI comparator and WDI
comparator will shut off, reducing the quiescent current drawn
by the IC to less than 1μA.
Condition
SW1/SW2
SW3/SW4
V
CC
> Reset Threshold
open
closed
V
CC
< Reset Threshold
V
CC
> V
BATT
open
closed
V
CC
< Reset Threshold
V
CC
< V
BATT
closed
open
ASM690A/802A/805L Reset Threshold = 4.65V
ASM692A /ASM802M Reset Threshold = 4.4V
Pin
Connection
V
OUT
Connected to V
BATT
through internal PMOS
switch
V
BATT
Connected to V
OUT
PFI
Disabled
PFO
Logic-LOW
RESET
Logic-LOW (except on ASM805 where it is
HIGH)
WDI
Watchdog timer disabled
SW1
SW2
D1
D2
SW3 SW4
D3
ASM690A
ASM692A
ASM802L
ASM802M
ASM805L
V
OUT
V
CC
V
BATT
Figure 3: Internal device configuration of battery
switch-over function
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PDF描述 |
|---|---|
| ASM802MCPA | UP Power Supply Supervisor With Battery Backup Switch |
| ASM802MCSA | UP Power Supply Supervisor With Battery Backup Switch |
| ASM802MESA | UP Power Supply Supervisor With Battery Backup Switch |
| ASM805L | UP Power Supply Supervisor With Battery Backup Switch |
| ASM805LCPA | UP Power Supply Supervisor With Battery Backup Switch |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| ASM802MCPA | 制造商:ALSC 制造商全稱:Alliance Semiconductor Corporation 功能描述:UP Power Supply Supervisor With Battery Backup Switch |
| ASM802MCPAF | 制造商:PULSECORE 制造商全稱:PulseCore Semiconductor 功能描述:μP Power Supply Supervisor With Battery Backup Switch |
| ASM802MCSA | 制造商:PULSECORE 制造商全稱:PulseCore Semiconductor 功能描述:μP Power Supply Supervisor With Battery Backup Switch |
| ASM802MCSAF | 制造商:PULSECORE 制造商全稱:PulseCore Semiconductor 功能描述:μP Power Supply Supervisor With Battery Backup Switch |
| ASM802MEPA | 制造商:ALSC 制造商全稱:Alliance Semiconductor Corporation 功能描述:UP Power Supply Supervisor With Battery Backup Switch |
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