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PTN7860W; about switching frequency

Karina Espejo
Prodigy 40 points
Other Parts Discussed in Thread: PTN78060W

Hi,

I have runned some measurements in the PTN7860W. I noticed that the GND-pin7 has "less noise" compared with GND-pin1. There was a spurious signal at GND-Pin1 500Khz, 200mV. I assumed that switching frequency gets couple into this GND at PIN1 via the air. Then this disturbance also appears in PIN4-adjust voltage. As you may observe in the docx. attached.

I wonder if it is ok to have one GND-pin1 with a spurious signal of around 200mVpp. I thought that input and output filters placed to the PTN7860W should handle this? or maybe the module is prepared to handle this? specially at PIN4-adjust voltage.

Thanks!

Karina

VgndPin7_VadjustPin4.docx
  • 0
    TI__Mastermind 38230 points

    Karina:

    PTN78060W recommended design is to use an adjust resistor from pin 4 ot pin7( ground0. The connect pin 7(ground) to pin 1( ground). The data  attached  is measuring E-field scope probe sensitivity. The e-field switching frequency scope data  does not affect the power module operation or performance.

    There is a filter  application section in PTN78060 specification  with filter components .

    Any ripple/noise scope probe measurements should be with a 20MHZ setting and measured probe close coupling  across a ceramic capacitor on either input or output capacitance. I attached the application note pages.

    Tom

    Any additional questions on this module can be sent  to tguerin@ti.com

     

    Pages from ptn78060 spec filter notes[1].pdf