LTC1921 Linear Technology, LTC1921 Datasheet - Page 4

• Manufacturer Part Number: LTC1921
• Description: Dual .48V Supply and Fuse Monitor
• Manufacturer: Linear Technology

PI FU CTIO S
LTC1921
TYPICAL PERFOR A CE CHARACTERISTICS
V
is compared to the valid supply voltage window and the
result is output at OUT A (Pin 5). Supply current is drawn
from this pin as well as from V
FUSE A (Pin 2): This pin monitors the state of a fuse by
comparing the voltage at this pin to the voltage at V
(Pin 1). The result is output at OUT F (Pin 4).
RTN (Pin 3): Supply Return Reference. This pin must be
at an equal or higher potential than the other pins and
should be wired to the – 48V return.
OUT F (Pin 4): This pin indicates the state of the external
fuses by ORing the comparisons made to the FUSE A and
FUSE B pins. If V
window around V
exhibit a high internal impedance to the RTN pin. If
V
internally to the RTN pin and can shunt enough current to
turn off an optocoupler or LED wired between these pins.
OUT F should be clamped externally so that it cannot be
driven more than 8V below RTN. This is done automati-
cally by the optocoupler or LED diodes shown in the
application circuits.
OUT A (Pin 5): Indicates the State of V
specified voltage window (neither undervoltage nor over-
voltage), OUT A will exhibit a high internal impedance to the
4
A
FUSEA
(Pin 1): Supply to be Monitored. The voltage at this pin
U
U
V
A
or V
10000
FUSEA
1000
100
A
FUSEB
) and V
U
4.5
Undervoltage Response Time
T
A
= 25 C
SUPPLY STEP FROM UNDERVOLTAGE
V
4.6
A
RECOVERY THRESHOLD (V)
(V
FUSEB
W
V
4.7
FUSEA
B
, then OUT F is shorted
B
4.8
U
(Pin 8).
is within the specified
V
4.9
A
B
. If V
, then OUT F will
5.0
A
is within the
5.1
1921 G10
5.2
A
OUT F pin. If V
undervoltage limits, then OUT A is shorted internally to the
OUT F pin and can shunt enough current to turn off an
optocoupler or LED wired between these pins. OUT A should
be clamped externally so that it cannot be driven more than
8V below RTN. This is done automatically by the
optocoupler or LED diodes shown in the application circuits.
OUT B (Pin 6): Indicates the State of V
specified voltage window (neither undervoltage nor over-
voltage), OUT B will exhibit a high internal impedance to the
OUT A pin. If V
undervoltage limits, then OUT B is shorted internally to the
OUT A pin and can shunt enough current to turn off an
optocoupler or LED wired between these pins. OUT B should
be clamped externally so that it cannot be driven more than
8V below RTN. This is done automatically by the
optocoupler or LED diodes shown in the application circuits.
FUSE B (Pin 7): This pin monitors the state of a fuse by
comparing the voltage at this pin to the voltage at V
(Pin 8). The result is output at OUT F (Pin 4).
V
is compared to the valid supply voltage window and the
result is output at OUT B (Pin 6). Supply current is drawn
from this pin as well as from V
B
(Pin 8): Supply to be Monitored. The voltage at this pin
10000
1000
100
1.3
Overvoltage Response Time
T
A
= 25 C
SUPPLY STEP FROM OVERVOLTAGE
1.5
A
B
RECOVERY THRESHOLD (V)
is outside the specified overvoltage or
is outside the specified overvoltage or
1.7
1.9
2.1
A
(Pin 1).
2.3
1921 G11
B
. If V
2.5
B
is within the
1921i
B