Fairchild Semiconductor RV4145A Datasheet

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RV4145A

Low Power Ground Fault Interrupter

Features

• No potentiomenter required

• Direct interface to SCR

• Supply voltage derived from AC line – 26V shunt

• Adjustable sensitivity

Description

The RV4145A 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.

• Grounded neutral fault detection

• Meets U.L. 943 standards

• 450µA quiescent current

• Ideal for 120V or 220V systems

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 RV4145A 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.

Block Diagram

+Input

REF

(+13V)

Ground

RV4145A

10K

6.5V

4.7K

6.5V

65-4145A-01

Op Amp Output

(+26V)

SCR Trigger

REV. 1.0.3 3/6/02

PRODUCT SPECIFICATION RV4145A

Pin Assignments

8-Pin PDIP

+Input

REF

GND

8-Pin SOIC

Op Amp Output

SCR Trigger

+Input

GND

REF

8-Pin MSOP

Op Amp Output

SCR Trigger

65-4145A-02

Absolute Maximum Ratings

(beyond which the device may be damaged)

Parameter Min Typ Max Units

Supply Current 18 mA

Internal Power Dissipation 500 mW

Storage Temperature Range -65 +150 °C

Operating Temperature Range -35 +85 °C

Junction Temperature 125°C

Lead Soldering Temperature 60 Sec, DIP 300 °C

< 50°C SOIC 300 mW

For T

> 50°C Derate at SOIC 4 mW/°C

Notes:

1. Functional operation under any of these conditions is NOT implied. Performance and reliability are guaranteed only if Operating Conditions are not exceeded.

10 Sec, SOIC, MSOP 260 °C

PDIP 450 mW

MSOP 350 mW

PDIP 6 mW/°C

MSOP 4.7 mW/°C

Operating Conditions

Parameter Min Typ Max Units

Thermal resistance SOIC 240 °C/W

PDIP 160 °C/W

MSOP 206 °C/W

REV. 1.0.3 3/6/02

≤

RV4145A PRODUCT SPECIFICATION

Electrical Characteristics

Parameters Test Conditions Min Typ Max Units

Detector Reference Voltage Pin 7 to Pin 3 6.8 7.2 8.1 ±V

Shunt Regulator

Zener Voltage (+V

Reference Voltage (V

Quiescent Current (I

Operational Ampliﬁer

Offset Voltage Pin 2 to Pin 3 -3.0 0.5 +3.0 mV

+Output Voltage Swing Pin 7 to Pin 3 6.8 7.2 8.1 V

–Output Voltage Swing Pin 7 to Pin 3 -9.5 -11.2 -13.5 V

+Output Source Current Pin 7 to Pin 3 650 µA

–Output Source Current Pin 7 to Pin 3 1.0 mA

Gain Bandwidth Product F = 50KHz 1.0 1.8 MHz

Resistors I

R1 Pin 1 to Pin 3 10 k Ω

R2 Pin 2 to Pin 3 10 k Ω

R3 Pin 5 to Pin 4 3.5 4.7 5.9 k Ω

SCR Trigger Voltage Pin 5 to Pin 4

Detector On 1.5 2.8 V

Detector Off 0 1 10 mV

) Pin 6 to Pin 4 25 26 29.2 V

) Pin 3 to Pin 4 12.5 13 14.6 V

REF

)+V

= 1.5mA and T

= 24V 450 750 µA

= 0mA

= +25°C)

Electrical Characteristics

Parameters Test Conditions Min Typ Max Units

Detector Reference Voltage Pin 7 to Pin 3 6.5 7.2 8.3 ±V

Shunt Regulator

Zener Voltage (+V

Reference Voltage (V

Quiescent Current (I

Operational Ampliﬁer

Offset Voltage Pin 2 to Pin 3 -5.0 0.5 +5.0 mV

+Output Voltage Swing Pin 7 to Pin 3 6.5 7.2 8.3 V

–Output Voltage Swing Pin 7 to Pin 3 -9 -11.2 -14 V

Gain Bandwidth Product F = 50KHz 1.8 MHz

Resistors I

R1 Pin 1 to Pin 3 10 k Ω

R2 Pin 2 to Pin 3 10 k Ω

R3 Pin 5 to Pin 4 3.5 4.7 5.9 k Ω

SCR Trigger Voltage Pin 5 to Pin 4

Detector On 1.3 2.8 V

Detector Off 0 3 50 mV

) Pin 6 to Pin 4 24 26 30 V

) Pin 3 to Pin 4 12 13 15 V

REF

)+V

= 1.5mA and -35°C ≤ T

= 23V 500 µA

= 0mA

+85°C)

REV. 1.0.3 3/6/02

PRODUCT SPECIFICATION RV4145A

Principles of Operation

The 26V shunt regulator voltage generated by the string of zener diodes is divided into three reference voltages: 3/4 V 1/2 V

, and 1/4 V

ence 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 RV4145A. Fault signals from the sense transformer are AC coupled into the input and are ampliﬁed according to the following equation:

= R

Where V R

SENSE

pin 7 to pin 1, I N is the turns ratio of the transformer. When V or minus 7.2V relative to pin 3 the SCR Trigger output will go high and ﬁre the external SCR.

The formula for V 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.

is the RMS voltage at pin 7 relative to pin 3,

is the value of the feedback resistor connected from

Shunt Regulator

limits the current into the shunt regulator; 220V

LINE

applications will require substituting a 47k Ω 2W resistor. In addition to supplying power to the IC, the shunt regulator creates internal reference voltages (see above).

Operational Ampliﬁer

R sensitivity to normal faults. To adjust R procedure: apply the desired fault current (a difference in current of 5mA is the UL 943 standard). Adjust R upward until the SCR activates. A ﬁxed resistor can be used for R will meet UL’s 943 4-6mA speciﬁcation window.

is a feedback resistor that sets gain and therefore

SENSE

. V

SENSE

, since the resultant ±15% variation in sensitivity

is at 1/2VS and is used as a refer-

REF

is approximate because it does not

SENSE

is the fault current in amps RMS and

exceeds plus

, follow this

SENSE

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 Ω or 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. C 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.

is a

Sense Transformers and Cores

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.

Magnetic Metals Corporation, Camden, NJ 08101, (609) 964-7842, and Magnetics, 900 E. Butler Road, P.O. Box 391, Butler, PA 16003, (412) 282-8282 are full line suppliers of ring cores and transformers designed speciﬁcally for GFI applications.

Two-Wire Application Circuit

Figure 2 shows the diagram of a 2-wire 120V AC outlet GFI circuit using an RV4145A. 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.

REV. 1.0.3 3/6/02

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