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TPS563209: TPS563209

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Replies: 3

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Part Number: TPS563209

We are using TPS563209 in our design.

This IC is with Fixed Frequency of 650KHz.

While capturing the waveform at SW node of this IC, We observed frequency variation from around 660Khz to 710Khz (Frequency found variation continuously in this range). Why this deviation? Please suggest,

This IC does not specified any frequency dithering.

Due to this variation in frequency, We are facing RF interference with LF RFID. Harmonics of this is getting couple to RFID Harmonics.

We have validated with Fixed DC load of 0.5A, 1A and 2A.

Input to the IC is 12VDC.

Output adjusted to 5V.

Attached are the Waveform at SW node of TPS563209. (In all three load condition, Frequency variation observed)

Load Condition 1 : 0.5A

Load Condition 2 : 1A

Load Condition 3 : 2A

  • Hi,

    That is the normal phenomenon, the control mode of this device is DCAP2, it is constant on time control, the switching frequency is not fixed.If you care about the variation of frequency, you need to choose a current mode control device, such as TPS54302/8, TPS56339.

    Shawn 

  • In reply to Shawn Nie:

    Hi,

    If Constant on time, Frequency should remain constant. Is it correct? Why is it deviating? Please advise. No clarity marked in datasheet for this.

    We have tied with TPS54308 but operating frequency is varying from 255Khz to 445 kHz. No stable control in this.

    What is other difference in TPS54308 and TPS563209 device? Please advice.

  • In reply to kalpesh diyora:

    Hi,

    For DCAP mode, the frequency is calculated internally, and to make it to be about 650KHz, it is not fixed.

    For TPS54308, it is current mode device, the frequency is decided by the clock, it is fixed.

    But for both this devoces, the frequency is related to the process, 255kHz to 445 kHz is the min and max value, if the frequency of the device is out of the range, it is regarded as a defective product. 

    TPS54308 and TPS563209 are pin to pin devices. The main difference is the control mode, TPS54308 is current mode, TPS563209 is DCAP mode. 

    Shawn