LTC2909 Linear Technology, LTC2909 Datasheet - Page 14

• Manufacturer Part Number: LTC2909
• Description: OV and Negative Voltage Monitor
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
LTC2909
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
TYPICAL APPLICATIO S
14
V
V
V
V
UV(FALLING)
OV(FALLING)
UV(RISING)
OV(RISING)
36V TO 72V
V
IN
: 43.3V
: 38.7V
: 71.6V
: 70.2V
48V Telecom UV/OV Monitor with Hysteresis
R
169k
P2A2
M1, M2: FDG6301N OR SIMILAR
IF LOADING OF RST WILL EXCEED 1nF,
A 1nF BYPASS CAPACITOR ON M1’s
DRAIN IS RECOMMENDED
R
18.7k
R
1.43M
M2
P1A
P2A
–15V
3.3V
2.5V
15V
–5V
U
5V
R
13.7k
R
1.91M
P1B
P2B
M1
R
3.09M
Six Supply Undervoltage Monitor with 2.5V Reset Output and 20ms Timeout
U
N2B
R
681k
P1B2
R
1.37M
R
133k
R
107k
N2A
N1A
N1B
U
0.25W
ADJ1
ADJ2
REF
W
LTC2909-2.5
R
27k
ADJ1
REF
ADJ2
CC
LTC2909-2.5
GND
V
CC
GND
V
100nF
C
CC
TMR
BYP
RST
SEL
C
100nF
BYP1
TMR
RST
SEL
U
2909 TA03
5V
R
10k
SYSTEM
PU
C
2.2nF
TMR1
R
10k
PU
C
2.2nF
TMR2
pulled above V
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 V
fault condition, V
0.15V at ⎯ R ⎯ S ⎯ T .
RST
SEL
TMR
LTC2909-3.3
PUSHBUTTON
GND
V
MANUAL
CC
RESET
100nF
C
BYP2
ADJ1
ADJ2
REF
–12V
12V, 20ms Timeout (1.8V Logic Out)
12V
±12V UV Monitor Powered from
CC
*OPTIONAL FOR ESD
10k*
2.49M
, providing the voltage limits of the pin
R
CC
N2
R
1.15M
R
137k
R
115k
of at least 0.5V guarantees a V
P2A
P1A
P1B
R
1.07M
R
49.9k
2909 TA02
P2
P1
107k
R
N1
R
3.09M
R
P2B
10k
CC
ADJ1
REF
ADJ2
LTC2909-2.5
SYSTEM
GND
V
www.DataSheet4U.com
CC
100nF
TMR
C
RST
SEL
BYP
2909 TA01b
1.8V
C
2.2nF
TMR
R
10k
CC
PU
. During a
FAULT
OUTPUT
OL
2909fa
of