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參數(shù)資料
| 型號(hào)： | MAX6744XKW |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Low-Power Dual-/Triple-Voltage SC70 UP Supervisory Circuits |
| 中文描述： | 低功耗Dual-/Triple-Voltage SC70封裝的監(jiān)控電路 |
| 文件頁(yè)數(shù)： | 12/16頁(yè) |
| 文件大?。?/td> | 209K |
| 代理商： | MAX6744XKW |
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M
Low-Power Dual-/Triple-Voltage SC70 μP
Supervisory Circuits
12
______________________________________________________________________________________
Adding Hysteresis to the
Power-Fail Comparator
The power-fail comparator has a typical input hystere-
sis of 2.5mV. This is sufficient for most applications in
which a power-supply line is being monitored through
an external voltage-divider. If additional noise margin is
desired, connect a resistor between
PFO
and PFI, as
shown in Figure 6. Select the values of R1, R2, and R3
such that PFI sees V
TH-PFI
(488mV) when V
EXT
falls to
its power-fail trip point (V
FAIL
) and when V
EXT
rises to
its power-good trip point (V
GOOD
). The hysteresis win-
dow extends between the specified V
FAIL
and V
GOOD
thresholds. R3 adds the additional hysteresis by sink-
ing current from the R1/R2 divider network when the
PFO
output is logic low and sourcing current into the
network when
PFO
is logic high. R3 is typically an order
of magnitude greater than R1 or R2.
The current through R2 should be at least 1μA to ensure
that the 10nA (max) PFI input current does not significant-
ly shift the trip points. Therefore, for most applications:
R2 < V
TH-PFI
/ 1mA < 0.488V / 1mA < 488k
PFO
is an open-drain output requiring an external
pullup resistor, R4. Select R4 to be less than 1% of R3.
V
GOOD
= DESIRED V
EXT
GOOD VOLTAGE THRESHOLD
V
FAIL
= DESIRED V
EXT
FAIL VOLTAGE THRESHOLD
V
PU
= V
PULLUP
(FOR OPEN-DRAIN
PFO
)
R2 = 488k
(FOR >1μA R2 CURRENT)
R3 = (R1 x V
PU
) / (V
GOOD
- V
FAIL
)
R4
≤
0.01 x R3
Power Sequencing Applications
Many dual-voltage processors/ASICs require specific
power-up/power-down sequences for the I/O and core
supplies.
R
R
V
V
V
V
V
V
V
GOOD
TH PFI
TH PFI
-
GOOD
FAIL
PU
TH
PFI
1
2
=
(
)
(
)
-
-
-
(
MAX6742
MAX6745
PFI
GND
V
EXT_TH
A) V
IN
IS POSITIVE
R1
R2
PFO
V
EXT_TH
= V
TH-PFI
R1 + R2
R2
(
)
MAX6742
MAX6745
PFI
GND
V
EXT_TH
V
CC
B) V
IN
IS NEGATIVE
R1
R2
PFO
V
EXT_TH
= R
2
1
R
1
1
R
2
V
CC
R
1
+
(
(
)
)
-
(V
TH-PFI
V
PFI
= 488mV
Figure 4. Using Power-Fail Input to Monitor an Additional
Power Supply
MAX6737
MAX6739
MAX6743
MAX6744
MAX6745
GND
GND
V
CC
1 V
CC
2
V
CC
2
V
CC
1
RESET
RESET TO OTHER SYSTEM COMPONENTS
RESET
μ
P
4.7k
Figure 5. Interfacing to μPs with Bidirectional Reset I/O
MAX6742
MAX6745
V
EXT
R1
R4
R3
R2
PFI
GND
PFO
V
GOOD
= DESIRED V
EXT
GOOD VOLTAGE THRESHOLD
V
FAIL
= DESIRED V
FAIL VOLTAGE THRESHOLD
V
= V
CC
1 (FOR PUSH-PULL PFO)
R2 = 200k
(FOR > 2.5
μ
A R2 CURRENT)
R1 = R2 ((V
GOOD
- V
TH-PFI
) - (V
TH-PFI
)(V
GOOD
- V
FAIL
) / V
PU
) / V
TH-PFI
R3 = (R1 x V
OH
) / (V
GOOD
- V
FAIL
V
GOOD
V
FAIL
V
IN
PFO
V
PULLUP
Figure 6. Adding Hysteresis to Power Fail for Push-Pull
PFO
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX6744XKY | Low-Power Dual-/Triple-Voltage SC70 UP Supervisory Circuits |
| MAX6744XKZ | Low-Power Dual-/Triple-Voltage SC70 UP Supervisory Circuits |
| MAX6737XKS | Low-Power Dual-/Triple-Voltage SC70 UP Supervisory Circuits |
| MAX6737XKT | Low-Power Dual-/Triple-Voltage SC70 UP Supervisory Circuits |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX6744XKWED3 | 制造商:Maxim Integrated Products 功能描述:LOW-POWER DUAL-/TRIPLE-VOLTAGE SC70 - Rail/Tube |
| MAX6744XKWED3+T | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)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(kāi)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 |
| MAX6744XKWED3-T | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)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(kāi)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 |
| MAX6744XKWED7 | 制造商:Maxim Integrated Products 功能描述:LOW-POWER DUAL-/TRIPLE-VOLTAGE SC70 - Rail/Tube |
| MAX6744XKWED7+T | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)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(kāi)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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