8 Detailed Description

8.1 Overview

The TPSF12C3 is an active electromagnetic interference (EMI) filter controller that is designed to reduce

common-mode (CM) conducted emissions in off-line power converter systems. The device senses the high-

frequency noise on each power line using a set of Y-rated capacitors, CSEN1-4, then injects noise-canceling

currents back into the power lines using a Y-rated capacitor CINJ along with damping circuitry that ensures

stability. The device includes integrated filtering, compensation and protection circuitry.

The TPSF12C3 provides a very low impedance path for CM noise in the frequency range of interest for EMI

measurement. This feature can achieve approximately 15 to 30 dB of CM noise reduction over the frequency

range of interest, for example, 100 kHz to 3 MHz, helping to reduce the size of common-mode chokes.

The TPSF12C3 operates over a supply voltage range of 8 V to 16 V and can withstand 18 V. The device

features include:

• Internal circuitry that simplifies compensation and design

• Built-in supply voltage UVLO to ensure proper operation

• Built-in thermal shutdown protection

• An EN input that allows power saving when the system is idling

The active EMI feature significantly reduces EMI filtering cost, size, and weight, while helping to meet CISPR 11

and CISPR 32 Class B EMI limits for conducted and radiated emissions.

Leveraging a pin arrangement designed for simple layout that requires relatively few external components, the

TPSF12C3 is specified for maximum ambient and junction temperatures of 105°C and 150°C, respectively.

8.2 Functional Block Diagram

Amp

Ref

Filter

VDD

VDD

VDD

SENSE1

SENSE2

SENSE3

SENSE4

REFGND

IGND

EN

VDD

VDD

COMP1

COMP2

INJ

+

–

GND

VDD

Supply

Phase1

Phase2

Phase3

Neutral

GND

GND

GND

Neutral

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TPSF12C3

SNVSCB8 – MARCH 2023

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Product Folder Links: TPSF12C3