JAJSOC5A march 2023 – april 2023 TPSF12C3
PRODUCTION DATA
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 to further reject line-frequency components appearing at the INJ output. Capacitor CG2 preserves gain at high frequencies, which extends the AEF bandwidth.
Choose a value for RG between 1 kΩ and 2 kΩ. A resistance of 1.5 kΩ is a common choice and selected in this example to set a midband gain of 50 dB. Choose capacitances for CG1 and CG2 of 10 nF and 10 pF, respectively, which establishes a gain rolloff below approximately 10 kHz for line- and low-frequency attenuation.