200:1

1000:1

HOT

NEUTRAL

Solenoid

C2

R6

R7

R8

Q1

SCR

ALARM

FT

VDD1

REF

FB

GND

SCR

OUT

VDD2

SCR_TST

R3

C1

R4

SW_OPEN

PH

PTT

R9

R11

LOAD

AFE3010

NG_OUT

SEL

D2

R1

R2

R5

R10

C4

R12

C3

C5

C6

C7

C8

C9

C10

D1

D3

C11

D4

8

AFE3010

SBFS042 – JUNE 2020

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Copyright © 2020, Texas Instruments Incorporated

7.3 Feature Description

7.3.1 Powering The AFE3010

Figure 7 shows the recommended components and configurations to develop a GFCI system using the

AFE3010. The AFE3010 features an internal 20-V shunt regulator that connects to an external rectifier output

through limiting resistors R1 and R2. The two separate VDD and GND pins offer redundancy during single

component failure events in GFCI systems. An internal 5-V rail powers the majority of the internal circuitry, and

drives all the signal pins except the NG_OUT, PH, and SCR_TST pins. The NG_OUT pin is referenced to the 20-

V VDD through an internal reverse blocking diode inside the device.

Figure 7. AFE3010 Application Diagram

7.3.2 Sensing Amplifier

The AFE3010 employs a current-feedback chopper amplifier topology to sense a wide range of fault currents

with high precision. The current-feedback topology allows the device to maintain consistent gain across the wide

fault current limits. Hence no degradation of accuracy is experienced at large fault current measurements. The

device REF, FB, and OUT pins are the noninverting, inverting, and output terminals of the amplifier, respectively.

The user access of all three pins helps system designers develop their own current sensing thresholds and

bandwidths by optimizing the corresponding passive component values.

7.3.3 Noise Filter

As shown in Figure 8, the AFE3010 uses a unique 2-stage filter architecture to provide robust protection against

false trips. A series of internal comparators register the fault current thresholds at the output of the sensing

amplifier. Once a valid fault threshold is detected, the filter searches for a pre-determined pattern of fault

occurrences in the consecutive cycles. If the specific pattern is detected, the filter will enable the SCR driver to

open the power line switch. As shown in Table 1, the AFE3010 response time is faster than the UL943 mandated

requirements.