9.2.1.2 Detailed Design Procedure

Table 9-2 gives the selected component values, which are the same as those used in the TPSF12C3 EVM. This

design uses a TVS diode placed at the low-voltage side of the inject capacitor for clamping during input surge

conditions.

Table 9-2. AEF Circuit Components for Application Circuit 1

REFERENCE

DESIGNATOR

QTY

SPECIFICATION

MANUFACTURER(1)

PART NUMBER

CSEN1, CSEN2,

CSEN3, CSEN4

4

Capacitor, ceramic, 680 pF, 300 VAC, Y2

MuRata

DE2B3SA681KN3AX02F

CINJ

1

Capacitor, ceramic, 4.7 nF, 300 VAC, Y2

MuRata

DE2E3SA472MA3BX02F

CD1

1

Capacitor, ceramic, 4.7 nF, 50 V, 0603

Various

–

CD2

1

Capacitor, ceramic, 22 nF, 50 V, 0603

Various

–

CD3

1

Capacitor, ceramic, 4.7 nF, 50 V, 0603

Various

–

CG1

1

Capacitor, ceramic, 10 nF, 50 V, 0603

Various

–

CG2

1

Capacitor, ceramic, 10 pF, 50 V, 0603

Various

–

CVDD

1

Capacitor, ceramic, 1 µF, 25 V, X7R, 0603

Various

–

DINJ

1

TVS diode, bidirectional, 24 V, SOD-323

Eaton

STS321240B301

RD1

1

Resistor, 1 kΩ, 0.1 W, 0603

Various

–

RD1A

1

Resistor, 50 Ω, 0.1 W, 0603

Various

–

RD2

1

Resistor, 200 Ω, 0.1 W, 0603

Various

–

RD3

1

Resistor, 698 Ω, 0.1 W, 0603

Various

–

RG

1

Resistor, 1.5 kΩ, 0.1 W, 0603

Various

–

U1

1

TPSF12C3 common-mode AEF IC for three-phase AC

power systems

Texas Instruments

TPSF12C3DYYR

(1)

See the Third-Party Products Disclaimer.

More generally, the TPSF12C3 AEF IC is designed to operate with a wide range of passive filter components

and system parameters.

9.2.1.2.1 Sense Capacitors

The sense pins of the TPSF12C3 feed into a second-order high-pass filter and signal combiner within the IC,

which rejects the line-frequency and DM components of the power line voltages, extracting the high-frequency

CM component.

The sense pins externally interface to the power lines using Y-rated capacitors, designated as CSEN1, CSEN2,

CSEN3 and CSEN4 in Figure 9-2. Choose Y2-rated sense capacitors of 680 pF, 300 VAC in this application to

establish voltages at the SENSE pins of 3-V peak-to-peak when operating at maximum line voltage.

9.2.1.2.2 Inject Capacitor

The INJ node interfaces to a power line using a Y-rated capacitor, designated as CINJ in Figure 9-2. Choose a

Y2-rated inject capacitor of 4.7 nF, 300 VAC in this design to accommodate an AC swing at INJ with at least a

2-V margin of headroom from the positive and negative supply rails.

The INJ pin biases at half the VDD supply voltage. Assuming a 12-V supply rail and allowing 2 V of upper and

lower headroom, this implies that a swing of ±4 V is available around the DC operating point.

9.2.1.2.3 Compensation Network

The CM noise signal derived from the internal sensing filter and summation network of the TPSF12C3 is

internally inverted and amplified by a gain stage. The components between the COMP1 and COMP2 pins of the

IC, designated as as RG, CG1 and CG2 in Figure 9-2, set the gain characteristic.

More specifically, resistor RG establishes a high midband AEF gain at frequencies where EMI filtering is required.

Capacitor CG1 increases the impedance of that branch at low frequencies, which sets a lower AEF amplifer gain

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