Low Power Ground Fault Interrupter

TECHNICAL DATA
Low Power Ground Fault Interrupter
IL4145A
The IL4145AN is a low power controller for AC outlet ground fault
interrupters. These devices detect hazardous grounding conditions, such as
equipment (connected to opposite phases of the AC line) in contact with a
pool of water and open circuits the line before a harmful or lethal shock
occurs.
Contained internally are a 26V zener shunt regulator, an op amp, and an SCR
driver. With the addition of two sense transformers, a bridge rectifier, an
SCR, a relay, and a few additional components, the IL4145AN will detect
and protect against both hot wire to ground and neutral wire to ground faults.
The simple layout and conventional design ensure ease of application and
long-term reliability.
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ORDERING INFORMATION
IL4145AN Plastic DIP
IL4145AD
SOIC
TA = -35 to 85 C for all packages.
No potentiometer required
Direct interface to SCR
Supply voltage derived from AC line – 26V shunt
Adjustable sensitivity
Grounded neutral fault detection
Meets U.L. 943 standards
450 μA quiescent current
Ideal for 120 V or 220 V systems
BLOCK DIAGRAM
VFB
+
R1
10K
+Input
Op Amp Output
R2
10K
VREF
(+13V)
6.5 V
6.5 V
+
6.5 V
6.5 V
+VS
(+26V)
+
Ground
PIN ASSIGNMENT
VFB
1
8
NC
+Input
2
7
Op Amp Output
VREF
3
6
+VS
GND
4
5
SCR Trigger
SCR Trigger
R3
4.7K
ABSOLUTE MAXIMUM RATINGS
Symbol
ICC
PD
Tstg
Topr
TJ
TL
PD
Parameter
Supply Current
Internal Power Dissipation
Storage Temperature Range
Operating Temperature Range
Junction Temperature
Lead Temperature
TA< 50°C
For TA> 50°C Derate at
Value
18
500
-65 to +150
-35 to +85
125
125
450
6
Unit
mA
mW
°C
°C
°C
°C
mW
mW/°C
* Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device.
These are stress ratings only and functional operation of the device at these or any other conditions beyond those
indicated under “recommended operating conditions” is not implied.
Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
January, 2011, rev.01
IL4145A
ELECTRICAL CHARACTERISTICS (IS= 1.5 mA and TA= +25°C)
Symbol
VOH
Parameter
Detector Reference Voltage
Test Condition
Min
Max
Unit
Pin 7 to Pin 3
6.8
8.1
±V
Shunt Regulator
+VS
Zener Voltage
Pin 6 to Pin 4
25
29.2
V
VREF
Reference Voltage
Pin 3 to Pin 4
12.5
14.6
V
IS
Quiescent Current
+VS = 24 V
750
μA
Operational Amplifier
VIO
Offset Voltage
Pin 2 to Pin 3
-3.0
+3.0
mV
VD
+Output Voltage Swing
Pin 7 to Pin 3
6.8
8.1
V
VOL
–Output Voltage Swing
Pin 7 to Pin 3
-13.5
-9.5
V
IOH
+Output Source Current
Pin 7 to Pin 3
-450
-850
μA
IOL
–Output Source Current
Pin 7 to Pin 3
800
1200
μA
Gain Bandwidth Product
1.0
R1
F = 50 KHz
IS = 0 mA
Pin 1 to Pin 3
8
12
kΩ
R2
Pin 2 to Pin 3
8
12
kΩ
Pin 5 to Pin 4
Pin 5 to Pin 4
3.5
5.9
kΩ
BW
Resistors
R1
R2
R3
R3
SCR Trigger Voltage
VON
Detector On
VOFF
MHz
1.5
Detector Off
V
0
10
mV
Min
Max
Unit
Pin 7 to Pin 3
6.5
8.3
±V
ELECTRICAL CHARACTERISTICS (IS= 1.5 mA and -35°C ≤ TA ≤ +85°C)
Symbol
VOH
Parameter
Detector Reference Voltage
Test Condition
Shunt Regulator
+VS
Zener Voltage
Pin 6 to Pin 4
24
30
V
VREF
Reference Voltage
Pin 3 to Pin 4
12
15
V
IS
Quiescent Current
+VS = 23 V
800
μA
Operational Amplifier
VIO
Offset Voltage
Pin 2 to Pin 3
-5.0
+5.0
mV
VD
+Output Voltage Swing
Pin 7 to Pin 3
6.5
8.3
V
–Output Voltage Swing
-14
-9
V
R1
Pin 7 to Pin 3
IS = 0 mA
Pin 1 to Pin 3
7.5
12.5
kΩ
R2
Pin 2 to Pin 3
7.5
12.5
kΩ
Pin 5 to Pin 4
Pin 5 to Pin 4
3.5
5.9
kΩ
VOL
Resistors
R1
R2
R3
R3
SCR Trigger Voltage
VON
Detector On
VOFF
Detector Off
1.3
0
V
50
mV
January, 2011, rev.01
IL4145A
Principles of Operation
The 26V shunt regulator voltage generated by the string
of zener diodes is divided into three reference voltages:
3/4 VS , 1/2 VS , and 1/4 VS . VREF is at 1/2VS and is
used as a reference to create an artifical ground of +13V
at the op amp noninverting input.
Figure 1 shows a three-wire 120V AC outlet GFI
application using an IL4145AN. Fault signals from the
sense transformer are AC coupled into the input and are
amplified according to the following equation:
V7 = RSENSE x ISENSE/N
Where V7 is the RMS voltage at pin 7 relative to pin 3,
RSENSE is the value of the feedback resistor connected
from pin 7 to pin 1, ISENSE is the fault current in amps
RMS and N is the turns ratio of the transformer. When
V7 exceeds plus or minus 7.2V relative to pin 3 the SCR
Trigger output will go high and fire the external SCR.
The formula for V7 is approximate because it does not
include the sense transformer characteristics.
Grounded neutral fault detection is accomplished when a
short or fault closes a magnetic path between the sense
transformer and the grounded neutral transformer. The
resultant AC coupling closes a positive feedback path
around the op amp, and therefore the op amp oscillates.
When the peaks of the oscillation voltage exceed the
SCR trigger comparator thresholds, the SCR output will
go high.
Adjust RSENSE upward until the SCR activates. A fixed
resistor can be used for RSENSE, since the resultant
±15% variation in sensitivity will meet UL’s 943 4-6mA
specification window.
The roll-off frequency is greater than the grounded
neutral fault oscillation frequency, in order to preserve
loop gain for oscillation (which is determined by the
inductance of the 200:1 transformer and C4).
The senstivity to grounded neutral faults is adjusted by
changing the frequency of oscillation. Increasing the
frequency reduces the sensitivity by reducing the loop
gain of the positive feedback circuit. As frequency
increases, the signal becomes attenuated and the loop
gain decreases. With the values shown the circuit will
detect a grounded neutral fault having resistance of 2
less.
The input to the op amp are protected from overvoltage
by back-toback diodes.
SCR Driver
The SCR used must have a high dV/dt rating to ensure
that line noise (generated by noisy appliances such as a
drill motor) does not falsely trigger the SCR. Also, the
SCR must have a gate drive requirement of less than
200μA. CF is a noise filter capacitor that prevents narrow
pulses from firing the SCR.
The relay solenoid used should have a 3ms or less
response time in order to meet the UL 943 timing
requirement.
Sense Transformers and Cores
Shunt Regulator
RLINE limits the current into the shunt regulator; 220V
applications will require substituting a 47k 2W resistor.
In addition to supplying power to the IC, the shunt
regulator creates internal reference voltages (see above).
Operational Amplifier
RSENSE is a feedback resistor that sets gain and
therefore sensitivity to normal faults. To adjust RSENSE,
follow this procedure: apply the desired fault current (a
difference in current of 5mA is the UL 943 standard).
The sense and grounded neutral transformer cores are
usually fabricated using high permeability laminated steel
rings. Their single turn primary is created by passing the
line and neutral wires through the center of its core. The
secondary is usually from 200 to 1500 turns.
Two-Wire Application Circuit
Figure 2 shows the diagram of a 2-wire 120V AC outlet
GFI circuit using an IL4145AN. This circuit is not
designed to detect grounded neutral faults. Thus, the
grounded neutral transformer and capacitors C3 and C4
of Figure 1 are not used.
January, 2011, rev.01
IL4145A
Press
To Test
RTEST
15K
MOV
Ground Neutral
Transformer
Sense Transformer
1000:1
Line
Latching
Contacts
K1
200:1
Hot
Neutral
RSENSE
1M*
C1
10F
Load
IL4145AN
VFB
Op Amp Output
VREF(+13V)
GND
C3
0.01 F
Solenoid
C4
0.03 F
+VS
SCR Trigger
DB1
1N4004 (4)
RLINE
24 K
Q1 ON Semi
MCR100-6
CF
2.2F
C2
0.01F
* Value depends on transformer characteristics.
Figure 1. GFI Application Circuit (Three-Wire Outlet)
January, 2011, rev.01
IL4145A
Press
To Test
RTEST
15K
MOV
Sense Transformer
1000:1
Line
Latching
Contacts
K1
Hot
Neutral
RSENSE
1M*
C1
10F
Load
IL4145AN
VFB
Op Amp Output
VREF(+13V)
GND
Solenoid
+VS
SCR Trigger
DB1
1N4004 (4)
RLINE
24 K
Q1 Tagi
X0103DA
CF
2.2F
C2
0.01F
* Value depends on transformer characteristics.
Figure 2. GFI Application Circuit (Two-Wire Outlet)
January, 2011, rev.01
+Input
(2)
VFB
(1)
Q21
C2
10 pF
Q22
(-)
R1
10K
Q4
Q1
R4
50K
Q6
Q3
R10
6K
Q5
Q2
R5
50K
(+)
Q7
R2
10K
Q8
4 pF
C1
Q9
Q23
Q11
Q10
R6
450
R14
1.3K
Q12
Q14
(7)
Z1
5.6V
Q15
R3
4.7K
R13
30K
Op Amp Output
R9
39K
Q13
R7
250K
Q17
6.5V
(5)
SCR Trigger
Sbstrate
R12
7.2K
Q16
Q18
6.5V
Q19
6.5V
Q20
6.5V
Ground
(4)
VREF
(+13V)
(3)
+VS(+26V)
(6)
IL4145A
SCHEMATIC DIAGRAM
January, 2011, rev.01
IL4145A
N SUFFIX PLASTIC DIP
(MS – 001BA)
A
Dimension, mm
5
8
B
1
4
F
Symbol
MIN
MAX
A
8.51
10.16
B
6.1
7.11
C
L
C
5.33
D
0.36
0.56
F
1.14
1.78
-T- SEATING
PLANE
N
G
M
K
0.25 (0.010) M
J
H
D
T
NOTES:
1. Dimensions “A”, “B” do not include mold flash or protrusions.
Maximum mold flash or protrusions 0.25 mm (0.010) per side.
G
2.54
H
7.62
J
0°
10°
K
2.92
3.81
L
7.62
8.26
M
0.2
0.36
N
0.38
D SUFFIX SOIC
(MS - 012AA)
Dimension, mm
A
8
5
B
H
1
G
P
4
D
K
MIN
MAX
A
4.8
5
B
3.8
4
C
1.35
1.75
D
0.33
0.51
F
0.4
1.27
R x 45
C
-T-
Symbol
SEATING
PLANE
J
F
0.25 (0.010) M T C M
NOTES:
1. Dimensions A and B do not include mold flash or protrusion.
2. Maximum mold flash or protrusion 0.15 mm (0.006) per side
for A; for B ‑ 0.25 mm (0.010) per side.
M
G
1.27
H
5.72
J
0°
8°
K
0.1
0.25
M
0.19
0.25
P
5.8
6.2
R
0.25
0.5
January, 2011, rev.01