LTC1921_15 Datasheet, PDF (1/12 Pages) Linear Technology – Dual 48V Supply and Fuse Monitor

FEATURES
s _{Withstands Transient Voltages Up to 200V/–200V}
s _{Requires No Precision External Components}
s _{Independently Monitors Two –48V Supplies for}
– Undervoltage Faults: –38.5V ±1V_MAX
– Overvoltage Faults: –70V ±1.5V_MAX
s _{Accurately Detects Undervoltage Fault Recovery:}
–43V ±0.5V_MAX
s _{Monitors Two External Fuses}
s _{Operates from –10V to –80V}
s _{Tolerates DC Faults to –100V}
s _{Tolerates Accidental Supply Reversal to 100V}
s _{Small Footprint: 8-Lead MSOP Package}
s _{Specified from – 40°C to 85°C}
U
APPLICATIO S
s _{Telecom Backplanes or Switch Cards}
s _{Networking Backplanes or Switch Cards}
s _{High Voltage Fuse Monitoring}
LTC1921
Dual –48V Supply
and Fuse Monitor
DESCRIPTIO
The LTC^®1921 monitors two independent – 48V supplies,
including their fuses, and drives up to three optoisolators
to indicate status, in accordance with standard backplane
specifications. Requiring only three noncritical resistors
and optoisolators, the LTC1921 replaces multiple voltage
comparators, a voltage reference and several precision
resistors.
The monitor features dual supply overvoltage and under-
voltage detection circuits. The preset trip thresholds in-
clude overvoltage, undervoltage and undervoltage recovery
that are guaranteed over temperature and meet or exceed
common backplane specifications. Additional built-in cir-
cuitry detects the condition of supply fuses. Overvoltage
and undervoltage detectors ignore fast supply transients,
eliminating false detection. The LTC1921 operates from
– 10V to – 80V with a typical power dissipation of less than
10mW.
The LTC1921 is available in 8-pin MSOP and SOIC pack-
ages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
– 48V
RETURN
R1
R2
100k
100k
47k 47k 47k
LOGIC
FUSE GOOD _SUPPLY
1
V_A
3
RTN
4
OUT F
8
V_B
LTC1921
2
FUSE A
7
5
FUSE B OUT A
MOC207
MOC207
SUPPLY A GOOD _SUPERVISOR
µP
SUPPLY B GOOD ^LOGIC
COMMON
–48V LOAD
F1
SUPPLY A
–48V
F2
SUPPLY B
–48V
6
OUT B
D1 MURS320
D2 MURS320
MOC207
R3
47k
1/4W
1921 TA01
1921f
1