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參數(shù)資料
| 型號(hào)： | MAX6728 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Replaced by TPL9202 : Microcontroller Power Supply and Low-Side Driver 20-HTSSOP -40 to 125 |
| 中文描述： | 雙/三路、超低電壓、SOT23封裝、微處理器監(jiān)控電路 |
| 文件頁數(shù)： | 12/19頁 |
| 文件大?。?/td> | 418K |
| 代理商： | MAX6728 |
M
Monitoring an Additional Power Supply
These μP supervisors can monitor either positive or
negative supplies using a resistor voltage-divider to
PFI.
PFO
can be used to generate an interrupt to the μP
or cause reset to assert (Figure 3).
Monitoring a Negative Voltage
The power-fail comparator can be used to monitor a
negative supply voltage using the circuit shown in
Figure 3. When the negative supply is valid,
PFO
is low.
When the negative supply voltage drops,
PFO
goes
high. The circuit
’
s accuracy is affected by the PFI
threshold tolerance, V
CC
, R1, and R2.
Negative-Going V
CC
Transients
The MAX6715
–
MAX6729 supervisors are relatively
immune to short-duration negative-going V
CC
transients
(glitches). It is usually undesirable to reset the μP when
V
CC
experiences only small glitches. The
Typical
Operating Characteristics
show Maximum Transient
Duration vs. Reset Threshold Overdrive, for which reset
pulses are not generated. The graph was produced
using negative-going V
CC
pulses, starting above V
TH
and ending below the reset threshold by the magnitude
indicated (reset threshold overdrive). The graph shows
the maximum pulse width that a negative-going V
CC
transient may typically have without causing a reset
pulse to be issued. As the amplitude of the transient
increases (i.e., goes farther below the reset threshold),
the maximum allowable pulse width decreases. A 0.1μF
bypass capacitor mounted close to the V
CC
pin pro-
vides additional transient immunity.
Watchdog Software Considerations
Setting and resetting the watchdog input at different
points in the program, rather than
“
pulsing
”
the watch-
dog input high-low-high or low-high-low, helps the
watchdog timer to closely monitor software execution.
This technique avoids a
“
stuck
”
loop where the watch-
dog timer continues to be reset within the loop, keeping
the watchdog from timing out. Figure 6 shows an exam-
ple flow diagram where the I/O driving the watchdog
input is set high at the beginning of the program, set low
at the beginning of every subroutine or loop, then set
high again when the program returns to the beginning. If
the program should
“
hang
”
in any subroutine, the I/O is
continually set low and the watchdog timer is allowed to
time out, causing a reset or interrupt to be issued.
Chip Information
TRANSISTOR COUNT: 1072
PROCESS: BiCMOS
Dual/Triple Ultra-Low-Voltage SOT23 μP
Supervisory Circuits
12
______________________________________________________________________________________
MAX6728/
MAX6729
V
EXT
R1
R3
R2
PFI
GND
PFO
A
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
PFI
) - (V
PFI
)(V
GOOD
- V
FAIL
) / V
OH
) / V
PFI
R3 = (R1 x V
OH
) / (V
GOOD
- V
FAIL
)
V
GOOD
V
FAIL
V
IN
PFO
Figure 5. Adding Hysteresis to Power-Fail for Push-Pull PFO
START
SET WDI
HIGH
PROGRAM
CODE
SUBROUTINE OR
PROGRAM LOOP
SET WDI LOW
RETURN
SUBROUTINE
COMPLETED
HANG IN
SUBROUTINE
Figure 6. Watchdog Flow Diagram
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX6729 | Replaced by TPL9202 : Microcontroller Power Supply and Low-Side Driver 20-HTSSOP -40 to 125 |
| MAX675EJA | +5V Precision Voltage Reference |
| MAX675CPA | 30V N-Channel PowerTrench MOSFET |
| MAX675CSA | 30V N-Channel PowerTrench MOSFET |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX6728AKALTD3+ | 制造商:Maxim Integrated Products 功能描述:MAXIM MAX6728AKALTD3+, SUPERVISORS - Boxed Product (Development Kits) 制造商:Maxim Integrated Products 功能描述:Maxim MAX6728AKALTD3+, Microprocessor Supervisory Circuit 4.625V/3.075V/Adj Reset Threshold 1.8V-5.0V VCC1 0.9V-3.3V VCC2 8-pin SOT23 |
| MAX6728AKALTD3+T | 功能描述:監(jiān)控電路 Dual uPower Supervisor 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 |
| MAX6728AKARVD3+ | 制造商:Maxim Integrated Products 功能描述:PROCESSOR SUPERVISOR 2.625V/1.575V 15UA 8PIN SOT-23 - Cut Tape Product |
| MAX6728AKARVD3+T | 功能描述:監(jiān)控電路 Dual uPower Supervisor 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 |
| MAX6728AKASDD3+ | 制造商:Maxim Integrated Products 功能描述:PROCESSOR SUPERVISOR 2.925V/0.788V 15UA 8PIN SOT-23 - Cut Tape Product |
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