DESCRIPTION
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.

FEATURES
■ Independently Monitors Two –48V Supplies for
   – Undervoltage Faults: –38.5V ±1VMAX
   – Overvoltage Faults: –70V ±1.5VMAX
■ Accurately Detects Undervoltage Fault Recovery:
   –43V ±0.5VMAX
■ Monitors Two External Fuses
■ Operates from –10V to –80V
■ Tolerates DC Faults to –100V
■ Tolerates Accidental Supply Reversal to 100V
■ Withstands Transient Voltages Up to 200V/–200V
■ Small Footprint: 8-Lead MSOP Package
■ Requires No Precision External Components
■ Specified from –40°C to 85°C

APPLICATIONS
■ Telecom Backplanes or Switch Cards
■ Networking Backplanes or Switch Cards
■ High Voltage Fuse Monitoring