LM1851 Unisonic Technologies, LM1851 Datasheet

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LM1851

Manufacturer Part Number
LM1851
Description
Ground Fault Interrupter
Manufacturer
Unisonic Technologies
Datasheet

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UTC LM1851
GROUND FAULT INTERRUPTER
DESCRIPTION
protection for AC power outlets in consumer and industrial
environments. Ground fault currents greater than a presentable
threshold value will trigger an external SCR-driven circuit
breaker to interrupt the AC line and remove the fault condition.
In addition to detection of conventional hot wire to ground faults,
the neutral fault condition is also detected.
to insure maximum immunity to false triggering due to line noise.
Special features include circuitry that rapidly resets the timing
capacitor in the event that noise pulses introduce 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
* 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
* Detects neutral line faults
PIN CONFIGURATION
UTC
vs neutral
The UTC LM1851 is designed to provide ground fault
Full advantage of the U.S. UL943 timing specification is taken
NON-INVERTING INPUT
INVERTING INPUT
SCR Trigger
UNISONIC TECHNOLOGIES CO., LTD.
GND
1
2
3
4
LINEAR INTEGRATED CIRCUIT
8
7
6
5
SENSE ITIVITY SET RESISTOR
SENSE AMPLIFIER OUTPUT
Vcc
TIMING CAPACITOR
DIP-8
SOP-8
QW-R122-007,A
1

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LM1851 Summary of contents

Page 1

... UTC LM1851 GROUND FAULT INTERRUPTER DESCRIPTION The UTC LM1851 is designed to provide ground fault protection for AC power outlets in consumer and industrial environments. Ground fault currents greater than a presentable threshold value will trigger an external SCR-driven circuit breaker to interrupt the AC line and remove the fault condition. ...

Page 2

... UTC LM1851 INTERNAL SCHEMATIC DIAGRAM UTC UNISONIC TECHNOLOGIES CO., LTD. LINEAR INTEGRATED CIRCUIT 2 QW-R122-007,A ...

Page 3

... UTC LM1851 BLOCK DIAGRAM Vcc SCR TRIGGER ABSOLUTE MAXIMUM RATINGS PARAMETER Supply Current Power Dissipation (Note 1) Operating Temperature Storage Temperature Lead Soldering Temperature DIP-8 (10 sec.) SOP-8 Vapor Phase (60 sec.) Infrared (15 sec.) DC ELECTRICAL CHARACTERISTICS PARAMETER Power Supply Shunt Regulator Pin 8, Average Value ...

Page 4

... FIGURE 1.Normal Fault Sensitivity Test Circuit CIRCUIT DESCRIPTION (Refer to Block and Connection Diagram) The UTC LM1851 operates from 26V as set by an internal shunt regulator, D3. In the absence of a fault (I feedback path status signal ( correspondingly zero. Under these conditions the capacitor discharge current, I ...

Page 5

... The correct value for R can also be determined from the characteristic curve that plots equation (3). Note that SET this is an approximate calculation; the exact value of R LM1851 tolerances. Inasmuch as UL943 specifies a sensitivity '' window '' of 4mA ~ 6mA, provision should be made to adjust per-product basis. SET ...

Page 6

... UTC LM1851 S1 LINE UL943 specifies ≤25 ms average trip time under these conditions. Calculation of C due to normal fault only is as follows: ≤25 ms Specification -3 ms GFI turn-on time (15k and 1μ Potential loss of one half-cycle due to fault current sense of half-cycles only -4 ms Time required to open a sluggish circuit breaker ≤ ...

Page 7

... UTC LM1851 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 difficult to quartile, but typically they sum with normal fault currents, thus allowing a larger value of C1. ...

Page 8

... UTC LM1851 DEFINITION OF TERMS Normal Fault An unintentional electrical path , R the load terminal of the hot line and the ground, as shown by the dashed lines HOT HOT GFI LINE NEUTRAL NEUTRAL R G Grounded Neutral Fault: An unintentional electrical path between the load terminal of the neutral line and the ground, as shown by the dashed lines ...

Page 9

... UTC LM1851 TYPICAL PERFORMANCE CHARACTERISTICS Average Trip Time vs Fault Current 1000 CIRCUIT OF FIGURE 2 100 UL943 NORMAL FAULT 10 0 0.01 0.1 1.0 TRIP TIME (SECONDS) Output Drive Current vs Output Voltage 1400 1200 1000 31V 800 5mA 8 600 400 1 1mA A 200 V PIN1 ...

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