FAN1851AMX Fairchild Semiconductor, FAN1851AMX Datasheet - Page 7

• Manufacturer Part Number: FAN1851AMX
• Description: IC CTRLR AC GRND FAULT 8SOIC
• Manufacturer: Fairchild Semiconductor

Specifications of FAN1851AMX

• Product: Voltage References
• Package / Case: SOIC-8
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PRODUCT SPECIFICATION
REV. 2.0.1 6/17/05
C T
=
where:
T = integration time
V = threshold voltage
I = average fault current into CT
therefore:
I
C T
=
----------------------------------------------------------------------------------------------------------------- -
⎛
⎝
input sense
transformer
⎛
⎝
------------------------ -
1000 turns
division of
120
-------- -
500
current generated
=
⎛
⎝
current
1 turn
120 V
------------------------------------ -
(swamps I
0.01 µF
⎞
⎠
heavy fault
⎛
⎝
-------------------- -
1.6
AC
R
B
⎞
⎠
0.4
+
rms
TH
0.4
)
⎞
⎠
charging
⎞
⎠
17.5
on half-
cycles
⎛
⎝
only
CT
⎛ ⎞
⎝ ⎠
----------- -
1000
1
-- -
2
1
current shunted
portion of fault
⎞
⎠
⎛
⎝
around GFI
---------------------- -
RG
⎛ ⎞
⎝ ⎠
1
-- -
2
RN
conversion
+
average
rms to
RN
0.91
0.91
⎞
⎠
0.008
(6)
(7)
In practice, the actual value of C
to include the effects of the neutral loop upon the net charg-
ing current. The effect of neutral loop induced currents is dif-
ficult to quantify, but typically they sum with normal fault
currents, thus allowing a larger value of C
requirements, 0.015µF has been found to be the best com-
promise between timing and noise.
For those GFI standards not requiring grounded neutral
detection, a still larger value capacity can be used and better
noise immunity obtained. The larger capacitor can be accom-
modated because R
full fault current, I, to enter the GFI.
In Figure 10, grounded neutral detection is accomplished by
feeding the neutral coil with 120Hz energy continuously and
allowing some of the energy to couple into the sense trans-
former during conditions of neutral fault.
Transformers may be obtained from Magnetic Metals, Inc.,
(http://www.magmet.com).
N
and R
G
are not present, allowing the
T
will have to be modified
T
. For UL943
FAN1851A
7