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參數(shù)資料
| 型號： | MAX801 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | 8-Pin レP Supervisory Circuits with 【1.5eset Accuracy |
| 中文描述： | 8引腳微處理器監(jiān)控電路，提供±1.5%的復(fù)位門限精度 |
| 文件頁數(shù)： | 8/12頁 |
| 文件大?。?/td> | 91K |
| 代理商： | MAX801 |
M
8-Pin μP S upervisory Circ uits
with ±1.5% Reset Ac c urac y
8
_______________________________________________________________________________________
_______________Detailed Desc ription
The MAX801/MAX808 microprocessor (μP) supervisory
circuits provide power-supply monitoring and backup-
battery switchover in μP systems. The MAX801 also
provides program-execution watchdog functions
(Figure 1). Use of BiCMOS technology results in an
improved, 1.5% reset-threshold precision while keeping
supply currents typically at 68μA (48μA for the
MAX808). The MAX801/MAX808 are intended for bat-
tery-powered applications that require high reset-
threshold precision, allowing a wide power-supply
operating range while preventing the system from oper-
ating below its specified voltage range.
RESET
and RES ET Outputs
The MAX801/MAX808’s
RESET
output ensures that the
μP powers up in a known state, and prevents code-
execution errors during power-down and brownout
conditions. It does this by resetting the μP, terminating
program execution when V
CC
dips below the reset
threshold. Each time
RESET
is asserted, it stays low for
at least the 200ms reset timeout period (set by an inter-
nal timer) to ensure the μP has adequate time to return
to an initial state. The internal timer restarts any time
V
CC
goes below the reset threshold (V
RST
) before the
reset timeout period is completed. The watchdog timer
on the MAX801 can also initiate a reset (see the
MAX801 Watchdog Timersection).
The
RESET
output is active low, and is implemented with
a strong pull-down/relatively weak pull-up structure. It is
guaranteed to be a logic low for 0V < V
CC
< V
RST
, pro-
vided V
BATT
is greater than 2V. Without a backup bat-
tery,
RESET
is guaranteed valid for V
CC
≥
1V.
The RESET output is the inverse of the
RESET
output; it
both sources and sinks current and cannot be wire-OR
connected.
Low-Line Comparator
The low-line comparator monitors V
CC
with a threshold
voltage typically 52mV above the reset threshold, with
13mV of hysteresis. Use
LOWLINE
to provide a non-
maskable interrupt (NMI) to the μP when power begins
to fall, initiating an orderly software shutdown routine. In
most battery-operated portable systems, reserve ener-
gy in the battery provides ample time to complete the
shutdown routine once the low-line warning is encoun-
tered and before reset asserts. If the system must con-
tend with a more rapid V
CC
fall time (such as when the
main battery is disconnected, when a DC-DC converter
shuts down, or when a high-side switch is opened dur-
ing normal operation), use capacitance on the V
CC
line
to provide time to execute the shutdown routine (Figure
3). First calculate the worst-case time required for the
system to perform its shutdown routine. Then, with
worst-case shutdown time, worst-case load current,
and minimum low-line to reset threshold (V
LR(min)
),
V
RESET
V
LOWLINE
V
CC
V
(MAX801)
V
(MAX808)
V
RST
V
LL
t
RP
t
RP
V
BATT
SHOWN FOR V
CC
= 0V to 5V, V
BATT
= 2.8V, CE IN = GND
Figure 2a. Timing Diagram, V
CC
Rising
V
RESET
V
LOWLINE
V
CC
V
(MAX801)
V
(MAX808)
V
RST
V
RST
+ V
LR
V
BATT
t
RCE
t
RD
t
RD
t
LL
SHOWN FOR V
CC
= 5V to 0V, V
BATT
= 2.8V, CE IN = GND
Figure 2b. Timing Diagram, V
CC
Falling
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| MAX801L | 8-Pin レP Supervisory Circuits with 【1.5eset Accuracy |
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| MAX801_CPA | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:8-Pin レP Supervisory Circuits with 【1.5eset Accuracy |
| MAX801_CSA | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:8-Pin レP Supervisory Circuits with 【1.5eset Accuracy |
| MAX801_EPA | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:8-Pin レP Supervisory Circuits with 【1.5eset Accuracy |
| MAX801_ESA | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:8-Pin レP Supervisory Circuits with 【1.5eset Accuracy |
| MAX801_MJA | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:8-Pin レP Supervisory Circuits with 【1.5eset Accuracy |
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