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Technical content
Features
For Two-Wire ALCI and RCD Applications Precision Sense Amplifier and Bandgap Reference Built-in AC Rectifier Direct DC Coupled to Sense Coil Built-in Noise Filter Low-Voltage SCR Disable SCR Gate Driver Adjustable Sensitivity Minimum External Components Meets UL 943B Requirements Ideal for 120V or 220V Systems Space-Saving SuperSOT™ 6-Pin Package
Applications
Personal Care Products Two-Wire Electrical Outlets, Circuit Breakers, and Power Cords Requiring GFI Safety Features ALCI and RCCB Circuits
Description
The FAN4146 is a low-power controller for AC outlet Appliance Leakage Circuit Interrupters (ALCI) and two- wire Residual Current Devices (RCD). The FAN4146 detects hazardous grounding conditions and open circuits the line before a harmful shock occurs. Internally, the FAN4146 contains a diode rectifier, precision bandgap 12V shunt regulator, precision low V OS offset-sense amplifier, time delay noise filter, window-detection comparators, and a SCR driver. With the addition of a minimum number of external components, the FAN4146 detects and protects against a hot-wire-to-ground fault. The minimum number of components and the small SuperSOT™ package allow for a small-form-factor, low-cost application solution. The FAN4146 circuitry has a built-in rectifier and shunt regulator that operates with a low quiescent current. This allows for a high-value, low-wattage-series supply resistor. The internal temperature compensated shunt regulator, sense amplifier, and bias circuitry provide for precision ground-fault detection. The low V OS offset- sense amplifier allows direct coupling of the sense coil to the amplifier’s feedback signal. This eliminates the large 50/60Hz AC-coupling capacitor. The internal delay filter rejects high-frequency noise spikes common with inductive loads. This decreas es false nuisance tripping. The internal SCR driver is temperature compensated and designed to satisfy the current requirements for a wide selection of external SCRs. The minimum number of external components and the 6-pin SuperSOT™ package enable for a low-cost, compact design and layout. The FAN4146ESX is an enhanced temperature range device.
Ordering Information
Temperature Range Package Packing Method FAN4146SX 0°C to +70°C 6-Lead SUPERSOT6 , JEDEC MO-193, 1.6mm Tape and Reel FAN4146ESX -25°C to +80°C 6-Lead SUPERSOT6, JEDEC MO-193, 1.6mm Tape and Reel
Figure 3. Block Diagram Figure 4. Pin Configuration
1 SCR Gate drive for external SCR
2 Neutral Supply input for FAN4146 circuitry
3 Line Supply input for FAN4146 circuitry
4 VREF Non-inverting input for current-sense amplifier
5 VFB Inverting input for current-sense amplifier
6 AmpOut External resistor connected to VFB sets the I fault sensitivity threshold
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN4146 • Rev. 1.0.0 4 FAN4146 — Ground Fault Interrupter Absolute Maximum Ratings Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. Symbol Parameter Condition Min. Max. Unit ICC Supply Current Continuous Current, Line to Neutral 15 mA VCC Supply Voltage Continuous Voltage, Line to Neutral -1.5 16.0 V All other pins Continuous Voltage to Neutral -0.8 15.0 V TSTG Storage Temperature Range -65 +150 °C ESD Electrostatic Discharge Capability Human Body Model, JESD22-A114 2500 V Charged Device Model, JESD22-C101 1000 Machine Model, JESD22-A115 200 Unless otherwise specified, TA=25°C, Ishunt=1mA. Symbol Parameter Conditions Min. Typ. Max. Units VREG Power Supply Shunt Regulator Voltage Line to Neutral 12.2 12.7 13.2 V Line to Neutral, Ishunt=-2mA -0.9 -0.7 IQ Quiescent Current Line to Neutral=10V 350 400 450 µA VREF Reference Voltage V REF to Neutral 5.8 6.0 6.2 V VTH Trip Threshold AmpOut to V REF 3.4 3.5 3.6 V VOS Amplifier Offset R SET=511KΩ, RIN=500Ω -450 0 450 µV IOS Amplifier Input Offset (5) Design Value -50 0 50 nA G Amplifier DC Gain (5) Design Value 100 dB fGBW Amplifier Gain Bandwidth (5) Design Value 1.5 MHz VSW+ Amplifier Positive Voltage Swing AmpOut to V REF, IFAULT=10µA 4.0 V VSW- Amplifier Negative Voltage Swing V REF to AmpOut, IFAULT=-10µA 4.0 V ISINK Amplifier Current Sink AmpOut=VREF + 3V, VFB=VREF + 100mV 400 µA ISRL Amplifier Current Source AmpOut=VREF – 3V, VFB=VREF - 100mV 400 µA td Delay Filter Delay from C1 Trip to SCR, LOW to HIGH 0.75 1.00 1.25 ms ROUT SCR Output Resistance SCR to Neutral=250mV, AmpOut=VREF 0.5 1.0 KΩ VOUT SCR Output Voltage SCR to Neutral, AmpOut=VREF 1 10 mV SCR to Neutral, AmpOut =VREF +4V 2.5 V IOUT SCR Output Current SCR to Neutral=1V AmpOut=VREF + 4V 350 500 µA Note: 5. Guaranteed by design; not tested in production.
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN4146 • Rev. 1.0.0 5 FAN4146 — Ground Fault Interrupter Functional Description Refer to Figure 1 and Figure 3. The FAN4146 is a two-wire GFCI controller for AC ground-fault-circuit interrupter s. The internal rectifier circuit is biased by the AC line during the positive half cycle of the AC line voltage. The internal 12V shunt regulator uses a precisi on temperature-compensated bandgap reference. The combination of precision reference circuitry and pr ecision sense amplifier provides for an accurate ground-fault tolerance. This allows for selection of external components with wider and lower-cost parameter variation. Due to the low quiescent current, a high value external series resistor 1) can be used which reduces the maximum power wattage required for this resistor. The 12V shunt regulator generates the reference voltage V REF for the sense amplifier’s (A 1) non-inverting input (AC ground reference) and supplies the bias for the delay timer (t 1), comparators (C1 & C2), and the SCR driver. The secondary winding of the sense transformer is directly DC coupled to the inverting input of the sense amplifier at pin 5 (V FB). The R SET resistor converts the sense transformer’s secondary current to a voltage at pin 6 (AmpOut). This voltage is compared to the internal window comparator (C 1 & C 2) and, when the AmpOut voltage exceeds the +/-V TH threshold voltage, the window comparator triggers the internal delay timer. The output of the window comparator must stay HIGH for the duration of the t 1 timer. If the window comparator’s output momentarily goes LOW, the t 1 timer resets. If the window comparator’s output is still HIGH at the end of the t 1 pulse, the SCR driver enables the current source I 1 and disables Q 1. The current source I 1 then enables the external SCR, which energizes the solenoid, opens the contact switches to the load, and removes the hazardous ground fault. The window comparator allows detection of a positive or negative I FAULT signal independent from the phase of the line voltage. An internal under-voltage lockout circuit disables the SCR driver if the voltage at pin 3 (LINE) is below 7.5V. This prevents the SCR from energizing the solenoid when the SCR’s anode voltage is below 65V. The sense transformer typically has a toroidal core made of laminated steel rings or solid ferrite material. The secondary of the transformer is typically 1000 turns of #40 wire wound through the toroid. The primary is typically one turn made by passing the AC hot and neutral wires through the center of the toroid. When a ground fault exists, a difference exists between the current flowing in hot and neutral wires. The primary difference current divided by the primary-to-secondary turns ratio is the current that flows through the secondary wire of the transformer. Calculation of RSET Resistor The AmpOut signal must exceed the window comparator’s V TH threshold voltage for longer than the delay timer and calculated by: VTH=IFAULT x 1.41 x RSET x COS(2π x (t/2P)) / N (1) RSET = (VTH x N) / (1.41 x IFAULT x COS(π x t/P)) (2) where: VTH =3 . 5 V IFAULT = 5mA (UL943B) t = 1ms (timer delay) P = Period of the AC Line (1/60Hz) N = Ratio of secondary to primary turns (1000:1) R SET = 505KΩ (511KΩ standard 1% value) In practice, the transformer is non-ideal, so R SET may need to be adjusted by up to 30% to obtain the desired I fault trip threshold. Calculation of VOS Trip Threshold Error Since the sense coil is directly connected to the feedback of the sense amplifier, the V OS offset introduces an I fault threshold error. This error can be calculated as follows: %Error=100 x (VOS x RSET) / (RIN + RLDC + RLAC) / VTH (3) where: VOS = +/-450µV (worst case) +/-150µV (typical) RSET = 511KΩ RIN = 470Ω (typical value) RLDC = 75Ω (sense coil secondary DC resistance) RLAC = 1.5 KΩ (AC(jωL) impedance of sense coil), L= 4H, f= 60Hz) VTH = 3.5V %Error= +/- 3.2% (worst case) +/- 1.1% (typical)
Figure 15. 6-Lead SUPERSOT6, JEDEC MO-193, 1.6mm Wide the warranty therein, which covers Fairchild products.
© 2010Fairchild Semiconductor Corporation www.fairchildsemi.com FAN4146 • Rev. 1.0.0 10 FAN4146 — Ground Fault Interrupter