LTC2909(RevA) データシートの表示（PDF） - Linear Technology
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LTC2909 Datasheet PDF : 16 Pages
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LTC2909
APPLICATIO S I FOR ATIO
This imposes a practical limit of 1μF (9 second timeout) if
the length of timeout during power-up needs to be longer
than 200ms. If the power-up timeout is not important,
larger capacitors may be used, subject to the limitation
that the capacitor leakage current must not exceed 500nA,
or the function of the timer will be impaired.
⎯R⎯S⎯T Output Characteristics
The DC characteristics of the ⎯R⎯S⎯T pull-down strength
are shown in the Typical Performance Characteristics
section. ⎯R⎯S⎯T is an open-drain pin and thus requires an
external pull-up resistor to the logic supply. ⎯R⎯S⎯T may be
pulled above VCC, providing the voltage limits of the pin
are observed.
The open-drain nature of the ⎯R⎯S⎯T pin allows for wired-OR
connection of several LTC2909s to monitor more than two
supplies (see Typical Applications). Other logic with open-
drain outputs may also connect to the ⎯R⎯S⎯T line, allowing
other logic-determined conditions to issue a reset.
As noted in the discussion of power up and power down,
the circuits that drive ⎯R⎯S⎯T are powered by VCC. During a
fault condition, VCC of at least 0.5V guarantees a VOL of
0.15V at ⎯R⎯S⎯T .
TYPICAL APPLICATIO S
Six Supply Undervoltage Monitor with 2.5V Reset Output and 20ms Timeout
15V
5V
–5V
–15V
3.3V
2.5V
CBYP1
100nF
RPU
10k
CBYP2
100nF
SYSTEM
RN2A
1.37M
RN2B RN1A
3.09M 133k
RN1B
107k
VCC
ADJ1
RST
LTC2909-2.5
REF
SEL
ADJ2
TMR
GND
CTMR1 CTMR2
2.2nF 2.2nF
VCC
RST
ADJ1
LTC2909-3.3
SEL
REF
TMR
ADJ2
GND
RP2A
1.15M
RP1A
137k
RP2B
3.09M
RP1B
115k
2909 TA02
48V Telecom UV/OV Monitor with Hysteresis
VIN
36V TO 72V
RP2A
1.43M
RP2B
1.91M
M2
RP2A2
169k
VUV(RISING): 43.3V
VUV(FALLING): 38.7V
VOV(RISING): 71.6V
VOV(FALLING): 70.2V
RP1A
18.7k
RP1B RP1B2
13.7k 681k
M1
RCC
27k
0.25W
CBYP
100nF
VCC
ADJ1
RST
LTC2909-2.5
ADJ2
SEL
REF
TMR
GND
M1, M2: FDG6301N OR SIMILAR
IF LOADING OF RST WILL EXCEED 1nF,
A 1nF BYPASS CAPACITOR ON M1’s
DRAIN IS RECOMMENDED
SYSTEM
5V
RPU
10k
2909 TA03
14
±12V UV Monitor Powered from
12V, 20ms Timeout (1.8V Logic Out)
CBYP
RCC
100nF
10k
12V
1.8V
RP2
1.07M
10k*
MANUAL
RESET
PUSHBUTTON
–12V
RP1
49.9k
RN2
RN1
2.49M 107k
*OPTIONAL FOR ESD
VCC
ADJ1
RST
LTC2909-2.5
REF
SEL
ADJ2
TMR
GND
RPU
10k
FAULT
OUTPUT
CTMR
2.2nF
2909 TA01b
2909fa
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