LM1851 Ground Fault Interrupter
June 1992
LM1851 Ground Fault Interrupter
General Description
The LM1851 is designed to provide ground fault protection
for AC power outlets in consumer and industrial environ-
ments Ground fault currents greater than a presettable
threshold value will trigger an external SCR-driven circuit
breaker to interrupt the AC line and remove the fault condi-
tion In addition to detection of conventional hot wire to
ground faults the neutral fault condition is also detected
Full advantage of the U S UL943 timing specification is tak-
en to insure maximum immunity to false triggering due to
line noise Special features include circuitry that rapidly re-
sets the timing capacitor in the event that noise pulses intro-
duce unwanted charging currents and a memory circuit that
allows firing of even a sluggish breaker on either half-cycle
of the line voltage when external full-wave rectification is
used
Features
Y
Y
Y
Y
Y
Y
Internal power supply shunt regulator
Externally programmable fault current threshold
Externally programmable fault current integration time
Direct interface to SCR
Operates under line reversal both load vs line and hot
vs neutral
Detects neutral line faults
Block and Connection Diagram
TL H 5177 – 1
Order Number LM1851M or LM1851N
See NS Package Number M08A or N08E
C
1995 National Semiconductor Corporation
TL H 5177
RRD-B30M115 Printed in U S A
NSC [ NATIONAL SEMICONDUCTOR ]
