Additional 100nF capacitance to the DA1469x VSUP_RF pin

Question

Hi, 
 
 We guess if an additional 100nF capacitance is added to the DA1469x VSUP_RF(V14) pin, the 1V2 LDO of radio which depends on VSUP_RF will be more stable, then the performance of range application will be improved because of the more stable refence voltage for RF ADC. 
 
 Could you kindly tell us the guess is OK or not? If the additional 100nF capacitance has no obviously bad effect to the range application performance, we want to try. 
 
 Best regards, 
 Peter

Peter Luo · Answer

Hi OV_Renesas， 
 Thank you so much! 
 We'll try the 100 nF cap in next PCB version. 
 Best Regards, 
 Peter

OV_Renesas · Answer

Hi Peter, All our characterization and evaluation is done with 10&mu;F ( ~7&mu;F effective @ DC-Bias = 1.4V) at V14 and VSUP_RF. On the characterization boards and the evaluation kits. Also, as far as we know, there is no difference in performance when operating on the internal Simo DCDC (ripple) or the internal LDOs (no ripple). The RF LDO should give enough isolation/rejection. You may try it of course, it will certainly not harm. But we do not believe that you are going to find any improvements. Best Regards, OV_Renesas

Peter Luo · Answer

Hi OV_Renesas, 
 Thanks for your so kind reply! 
 If the range source I/Q signals is modulated under rate 1mbps or 2mbps, the RF LDO do have enough isolation/rejection. 
 We are trying to use some 4mbps I/Q signals, the result is good, but the receiver sensitivity is not good enough, so we want to try any way to improve it. 
 Thank you again! 
 Best regards, 
 Peter

OV_Renesas · Answer

Hi Peter, Thank you for the reply. No problems are expected trying with 100 nF additional at VSUP_RF. In our older chips, with radio being more sensitive to HF supply ripple/noise we applied a small (printed) inductor and a shunt capacitor. To form a low-pass filter between V14 and V14_RF. Maybe this could be considered together with the 100 nF cap. Best Regards, OV_Renesas

Additional 100nF capacitance to the DA1469x VSUP_RF pin

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