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| 型號： | MAX819M |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | +5V Microprocessor Supervisory Circuits |
| 中文描述： | +5V微處理器監(jiān)控電路 |
| 文件頁數(shù)： | 9/16頁 |
| 文件大?。?/td> | 114K |
| 代理商： | MAX819M |
M
+5V Mic roproc essor S upervisory Circ uits
_______________________________________________________________________________________
9
_______________Detailed Desc ription
General T iming Charac teristic s
Designed for 5V systems, the MAX817/MAX818/
MAX819 provide a number of microprocessor (μP)
supervisory functions (see the Selector Guide on the
first page). Figure 2 shows the typical timing relation-
ships of the various outputs during power-up and
power-down with typical V
CC
rise and fall times.
RES ET Output
A μP’s reset input starts the μP in a known state. The
MAX817/MAX818/MAX819 μP supervisory circuits
assert a reset to prevent code-execution errors during
power-up, power-down, and brownout conditions.
RESET
is guaranteed to be a logic low for 0V < V
CC
<
V
RST
if V
BATT
is greater than 1V. Without a backup bat-
tery (V
BATT
= GND)
RESET
is guaranteed valid for
V
CC
≥
1V. Once V
CC
exceeds the reset threshold an
internal timer keeps
RESET
low for the reset timeout
period, t
RP
. After this interval
RESET
returns high
(Figure 2).
If a brownout condition occurs (V
CC
drops below the
reset threshold),
RESET
goes low. Each time
RESET
is
asserted it stays low for at least the reset timeout peri-
od. Any time V
CC
goes below the reset threshold the
internal timer clears. The reset timer starts when V
CC
returns above the reset threshold.
RESET
both sources
and sinks current.
Manual Reset Input (MAX 819)
Many μP-based products require manual reset capabil-
ity, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. On the MAX819, a logic
low on
MR
asserts reset. Reset remains asserted while
MR
is low, and for t
RP
(200ms) after it returns high.
During the reset timeout period (t
RP
),
MR
’s state is
ignored if the battery freshness seal is enabled.
MR
has
an internal 63k
pull-up resistor, so it can be left open
if not used. This input can be driven with TTL/CMOS-
logic levels or with open-drain/collector outputs.
Connect a normally open momentary switch from
MR
to
GND to create a manual reset function; external
debounce circuitry is not required. If
MR
is driven from
long cables or the device is used in a noisy environ-
ment, connect a 0.1μF capacitor from
MR
to GND to
provide additional noise immunity.
Note that
MR
must be high or open to enable the bat-
tery freshness seal. Once the battery freshness seal is
enabled its operation is unaffected by
MR
.
Battery Freshness S eal
The MAX817/MAX818/MAX819 battery freshness seal
disconnects the backup battery from internal circuitry
and OUT until it is needed. This allows an OEM to
ensure that the backup battery connected to BATT will
be fresh when the final product is put to use. To enable
the freshness seal on the MAX817 and MAX819:
1) Connect a battery to BATT.
2) Ground
PFO.
3) Bring V
CC
above the reset threshold and hold it
there until reset is deasserted following the reset
timeout period.
4) Bring V
CC
down again (Figure 3).
Use the same procedure for the MAX818, but ground
CE
OUT instead of
PFO
. Once the battery freshness
seal is enabled (disconnecting the backup battery from
internal circuitry and anything connected to OUT), it
remains enabled until V
CC
is brought above V
RST
.
Figure 2. Power-Up and Power-Down Timing
V
CC
CE OUT FOLLOWS CE IN
*MAX817/MAX819 ONLY.
*
V
OUT
t
RP
V
RST
V
BATT
V
BATT
V
BATT
V
BATT
V
RST
V
RESET
V
CE OUT**
V
PFO*
RESET TO
CE OUT
DELAY**
PFOFOLLOWS PFI
Figure 3. Battery Freshness Seal Timing
V
CC
RESET
t
RP
V
RST
V
RST
CE OUT (MAX818)
(EXTERNALLY HELD AT 0V)
CE OUT STATE LATCHED
AT 1/2 t
RP
AND 3/4 t
RP
,
FRESHNESS SEAL ENABLED
PFO (MAX817/MAX819)
(EXTERNALLY HELD AT 0V)
PFOSTATE LATCHED
AT 1/2 t
RP
AND 3/4 t
RP
,
FRESHNESS SEAL ENABLED
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX819MCPA | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX819MCPA+ | 功能描述:監(jiān)控電路 5V MPU Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX819MCSA | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX819MCSA+ | 功能描述:監(jiān)控電路 5V MPU Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX819MCSA+T | 功能描述:監(jiān)控電路 5V MPU Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
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