FAN1851AN

FAN1851AN Datasheet

FAN1851A

Part	Datasheet
FAN1851AN	FAN1851AN (pdf)

Related Parts	Information
FAN1851AMX	FAN1851AMX

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FAN1851A Ground Fault Interrupter • Improved performance over industry equivalents Tight fault current range Typ ±100µA Temperature compensated fault current characteristics No external trimming required • Direct interface to SCR • Supply voltage derived from AC shunt • Adjustable sensitivity • Grounded neutral fault detection • Meets UL943 standards • 450µA quiescent current • Ideal for 120V or 220V systems • Package options 8L DIP and 8L SOIC The FAN1851A is a controller for AC outlet ground fault interrupters. These devices detect hazardous grounding conditions example a pool of water or an 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 specification is taken to ensure maximum immunity to false triggering due to line noise. A special feature in the circuitry rapidly resets the integrating timing capacitor in the event that noise pulses introduce unwanted charging currents. Also, a flip-flop is included that ensures firing of even a slow circuit breaker relay on either of the two half-cycles of the line voltage when external full wave rectification is used. The application circuit can be configured to detect both normal faults hot wire to ground and grounded neutral faults. Block Diagram Timing Capacitor Sensitivity Set Resistor Sense Amplifier Output SCR Trigger Latch IF Q1 ITH for IF > 0 3ITH for IF = 0 A1 IF D1 +VS Q5 D2 Ground Inverting Input Non-Inverting Input FAN1851A Pin Assignments SCR Trigger Input + Input Ground RSET Amp Out PRODUCT SPECIFICATION Functional Description The voltage at the supply pin is clamped to +26V by the internal shunt regulator D3. This shunt regulator also generates an artificial ground voltage for the noninverting input of A1 shown as a +10V source . A1, Q1, and Q2 together act as a current mirror for fault current signals which are derived from an external transformer . When a fault signal is present, the mirrored current charges the external timing capacitor until its voltage exceeds the latch trigger threshold typically 17.5V . When this threshold is exceeded, the latch engages and Q3 turns off, allowing I2 to drive the SCR connected to the "SCR Trigger" pin. Extra Circuitry in the feedback path of A1 works with the switched current source I1 to remove any charge on CT induced by noise in the transformer. If no fault current is present, then I1 discharges CT with a current equal to 3 ITH, where ITH is the value of current set by the external RSET resistor. If fault signals are present at the input of A1 which is held at virtual ground, +10V , one of the two current mirrors in the feedback path of A1 Q4 and Q5 will become active, depending on which half-cycle the fault occurs. This action will raise the voltage at VS, switching I1 to a value equal to ITH, and reducing the discharge rate of CT to better allow fault currents to charge it. Notice that ITH discharges CT during both half-cycles of the line, while IF only charges CT during the half-cycle in which IF exits the "- Input" pin since Q1 will only carry fault current in one direction . Thus, during one half-cycle, IF-ITH charges CT, while during the other half-cycle ITH discharges it. Definition of Terms Normal Fault An unintentional electrical path, RB, between the load terminal of the hot line and the ground, as shown by the dashed lines in Figure1. Grounded Neutral Fault: An unintentional electrical path between the load terminal of the neutral line and the ground, as shown by the dashed lines in Figure Line Ordering Information Part Number FAN1851AN FAN1851AMX Package 8-lead Plastic DIP 8-lead Plastic SOIC Pb-Free Yes Operating Temperature Range Packing Method -40°C to +70°C Rail -40°C to +70°C Tape and Reel DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: Life support devices or systems are devices or systems which, a are intended for surgical implant into the body, or b support or sustain life, and c whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. A critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.

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FAN1851A

Ground Fault Interrupter
• Improved performance over industry equivalents Tight fault current range Typ ±100µA Temperature compensated fault current characteristics No external trimming required
• Direct interface to SCR
• Supply voltage derived from AC shunt
• Adjustable sensitivity
• Grounded neutral fault detection
• Meets UL943 standards
• 450µA quiescent current
• Ideal for 120V or 220V systems
• Package options 8L DIP and 8L SOIC

The FAN1851A is a controller for AC outlet ground fault interrupters. These devices detect hazardous grounding conditions example a pool of water or an 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 specification is taken to ensure maximum immunity to false triggering due to line noise. A special feature in the circuitry rapidly resets the integrating timing capacitor in the event that noise pulses introduce unwanted charging currents. Also, a flip-flop is included that ensures firing of even a slow circuit breaker relay on either of the two half-cycles of the line voltage when external full wave rectification is used.

The application circuit can be configured to detect both normal faults hot wire to ground and grounded neutral faults.

Block Diagram

Timing

Capacitor

Sensitivity Set Resistor

Sense Amplifier Output

SCR Trigger

Latch

IF Q1

ITH for IF > 0 3ITH for IF = 0

A1 IF

D1 +VS

Q5 D2

Ground

Inverting Input

Non-Inverting Input

FAN1851A

Pin Assignments

SCR Trigger

Input
+ Input

Ground

RSET

Amp Out

PRODUCT SPECIFICATION

Functional Description

The voltage at the supply pin is clamped to +26V by the internal shunt regulator D3. This shunt regulator also generates an artificial ground voltage for the noninverting input of A1 shown as a +10V source . A1, Q1, and Q2 together act as a current mirror for fault current signals which are derived from an external transformer . When a fault signal is present, the mirrored current charges the external timing capacitor until its voltage exceeds the latch trigger threshold typically 17.5V . When this threshold is exceeded, the latch engages and Q3 turns off, allowing I2 to drive the SCR connected to the "SCR Trigger" pin.

Extra Circuitry in the feedback path of A1 works with the switched current source I1 to remove any charge on CT induced by noise in the transformer. If no fault current is present, then I1 discharges CT with a current equal to 3 ITH,
where ITH is the value of current set by the external RSET resistor. If fault signals are present at the input of A1 which is held at virtual ground, +10V , one of the two current mirrors in the feedback path of A1 Q4 and Q5 will become active, depending on which half-cycle the fault occurs. This action will raise the voltage at VS, switching I1 to a value equal to ITH, and reducing the discharge rate of CT to better allow fault currents to charge it.

Notice that ITH discharges CT during both half-cycles of the line, while IF only charges CT during the half-cycle in which IF exits the "- Input" pin since Q1 will only carry fault current in one direction . Thus, during one half-cycle, IF-ITH charges CT, while during the other half-cycle ITH discharges it.

Definition of Terms

Normal Fault An unintentional electrical path, RB, between the load terminal of the hot line and the ground, as shown by the dashed lines in Figure1.

Grounded Neutral Fault:

An unintentional electrical path between the load terminal of the neutral line and the ground, as shown by the dashed lines in Figure

Line
Ordering Information

Part Number FAN1851AN FAN1851AMX

Package 8-lead Plastic DIP 8-lead Plastic SOIC

Pb-Free Yes

Operating Temperature Range Packing Method
-40°C to +70°C

Rail
-40°C to +70°C

Tape and Reel

DISCLAIMER

FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.

LIFE SUPPORT POLICY

FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein:

Life support devices or systems are devices or systems which, a are intended for surgical implant into the body, or b support or sustain life, and c whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user.

A critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.

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Datasheet ID: FAN1851AN 513879