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LTC5564 and  DC1646A noisy VCOMP?

Question asked by GerardD on Aug 3, 2018
Latest reply on Aug 7, 2018 by GerardD

Hi,

 

I'm testing the DC1646A (demo board for the RF power detector LTC5564) and I'm having trouble getting a clean VCOMP. I'm not sure if it is due to noise or if I need to adjust some elements of the demo PCB.

 

I'm attaching some measurements. Parameters:

VCC = 5V, RFIN = 5.8 GHz, input power at the demo board 0 dBm.

CH1 (yellow) is VOUT

CH2(cyan) is VCOMP.

GAIN 1, otherwise I will specify it.

 

- NO RFIN.

 

 

- RFIN ON.

 

- RFIN OFF. (Now also showing VCOMP)

 

- RFIN OFF, VREF = 0.34V. Notice how VOUT has some transients and VCOMP goes high. The threshold, VREF 340 mV, is far from the 282 mV of VOUT.

 

-RFIN ON, VREF = 0.34 V. Looks like VOUT is noisy when VREF is ON. VCOMP is HIGH (makes sense since VOUT>>VREF)

 

-RFIN ON, VREF = 0.84  V. Now VCOMP is LOW (makes sense since VOUT<VREF)

 

-RFIN ON, VREF = 0.470  V. Now VCOMP is going LOW too often. As far as I understand, this is not how it should be since VOUT>VREF.

- RFIN ON, VREF = 0.70  V. Now VCOMP is going HIGH sometimes. As far as I understand, this is not how it should be since VOUT<<VREF.

 

 

 

 

Is this how it is supposed to work? I'm using a R&S lab power supply, I'm assuming it is a fairly clean power supply. 

 

Thank you,

Gerard

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