LMX2615-SP: Capacitors value for VrefVCO, VrefVCO2, VbiasVCO, VbiasVCO2, VbiasBARAC

Noriyuki Takahashi

Part Number: LMX2615-SP

Hi team

It seems that 10uF is required for for VrefVCO, VrefVCO2, VbiasVCO, VbiasVCO2, VbiasBARAC, but can they use smaller capacitor value for these pins?

If 10uF is mandatory, could you tell the reason why 10uF is required for these pins?

Regards,

Noriyuki Takahashi

over 2 years ago

0 Noel Fung over 2 years ago

TI__Guru* 81400 points

Hi Takahashi-san,

These pins are internal LDOs output pins, we need a bypass capacitor at each pin to filter the noise. A smaller capacitor is fine (between 1µF and 10µF) but as we used 10µF during qualification, I suggest keep using 10µF at these pins.

0 Noriyuki Takahashi over 2 years ago in reply to Noel Fung

TI__Genius 9245 points

Noel,

If they use smaller capacitors, what may happen?

Regards,

Noriyuki Takahashi

+1 Noel Fung over 2 years ago in reply to Noriyuki Takahashi

TI__Guru* 81400 points

Hi Takahashi-san,

A smaller capacitor may not have sufficient filtering to the LDO noises, as a result, these noises may contaminate the VCO. In addition, the LDOs may become unstable, if the capacitors are too small.

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LMX2615-SP: Capacitors value for VrefVCO, VrefVCO2, VbiasVCO, VbiasVCO2, VbiasBARAC