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TPS61175: About ripple voltage of TPS61175

Part Number: TPS61175

I have revived question from customer. 

In the data sheet, the ripple voltage is specified by the output capacitor of TPS61175.

However, it seems that the calculation formula and the measured waveform are different.

When Vin 5.5V, Vout 13.0V, Iout 1A, SW 1.2MHz, Cout 47uF

In the calculation formula, the ripple voltage is about 10mV.

If you add the ESR component, it will be 15mV.

Please tell us about the difference between this calculation formula and measured value.

Best regards,

Katsuragawa

 
御社のデータシートから、
TPS61175の出力コンデンサによりリップル電圧が規定されておりますが、
計算式と実測の波形が異なっているように考えられます。
 
Vin 5.5V,Vout 13.0V,Iout 1A,SW 1.2MHz,Cout 47uFのとき、
計算式ではリップル電圧は約10mVとなりました。
それにESR分を加味すると15mVとなります。
 
こちらの計算式と実測との差分についてご教示ください。

  • Hi Katsuragawa-San:

    The Vripple-ESR should be consider together with Vripple. (Check datasheet "8.2.2.9 Selecting the Input and Output Capacitors") 

    Did customer forget to attach the measured value? As I don't find it. 

    What's the type of capacitance does customer use? If it's MLCC, you should take the DC-bias factor for capacity into considered. And no matter it's MLCC or tantalum or electrolytic capacitors, it's better to add some small value MLCC cap in parallel to reduce some parasitic parameters.

  • Dear Sir,

    What is you measured result?  Is it much higher than 15mV?