鈥?/div>
Grounded neutral fault detection
Meets UL943 standards
450
mA
quiescent current
Ideal for 120V or 220V systems
Description
The LM1851 is a controller for AC outlet ground fault
interrupters. These devices detect hazardous grounding con-
ditions (example: a pool of water and electrical equipment
connected to opposite phases of the AC line) in consumer
and industrial environments. The output of the IC triggers an
external SCR, which in turn opens a relay circuit breaker to
prevent a harmful or lethal shock.
Full advantage of the U.S. UL943 timing speci鏗乧ation is
taken to ensure maximum immunity to false triggering due
to line noise. A special feature is found in circuitry that
rapidly resets the integrating timing capacitor in the event
that noise pulses introduce unwanted charging currents.
Also, 鏗俰p-鏗俹p is included that ensures 鏗乺ing of even a slow
circuit breaker relay on either half-cycle of the line voltage
when external full wave recti鏗乧ation is used.
The application circuit can be con鏗乬ured to detect both
normal faults (hot wire to ground) and grounded neutral
faults.
Block Diagram
+V
S
Timing
Capacitor
Sensitivity
Set Resistor
Sense Amplifier
Output
I
TH
D3
I
2
Q2
SCR Trigger
Q3
Latch
Q1
I
F
I
TH
= I
TH
for I
F
> 0
3I
TH
for I
F
= 0
D1
A1
Q4
I
F
+V
S
Q5
D2
10V
Ground
65-1851-01
Inverting Input
Non-Inverting Input
Rev. 1.0.0