LM1851M National Semiconductor, LM1851M Datasheet - Page 6

• Manufacturer Part Number: LM1851M
• Description: IC,Ground Fault Interrupter,BIPOLAR,SOP,8PIN,PLASTIC
• Manufacturer: National Semiconductor

Specifications of LM1851M

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Application Circuits
in practice the actual value of C1 will have to be modified to
include the effects of the neutral loop upon the net charging
current The effect of neutral loop induced currents is diffi-
cult to quantize but typically they sum with normal fault cur-
rents thus allowing a larger value of C1
For UL943 requirements 0 015
the best compromise between timing and noise
Typical Application
Adjust R
SET
for desired sensitivity
(Continued)
F has been found to be
FIGURE 2 120 Hz Neutral Transformer Approach
6
For those GFI standards not requiring grounded neutral de-
tection a still larger value capacitor can be used and better
noise immunity obtained The larger capacitor can be ac-
commodated because R
the full fault current I to enter the GFI
In Figure 2 grounded neutral detection is accomplished by
feeding the neutral coil with 120 Hz energy continuously and
allowing some of the energy to couple into the sense trans-
former during conditions of neutral fault
N
and R
G
are not present allowing
TL H 5177– 6