BG_RBIAS Resistor precision

Question

Hi, 
 
 I am trying to debug our ADMV1014 design with low gain. We are currently using a 1k and 100 Ohm resistor in series (1% precision) as our resistor for the BG_RBIAS pin. I notice that you can control the quadrupler band gap with address 0x03. I can control this, by turning it off, our gain goes to -70dB, so I assume this stops the LO quadrupler working. My question is, does the 1k1 precision resistor have an effect on gain/LO drive to the mixer? Should we be using a much higher precision resistor at this pin?

Taz · Accepted Answer

Hi, 
 The eval board uses the panasonic ERJ-2GEJ112X 1.1k ohm resistor. As long as it is within 5% we haven't seen an issue. Typically when we have seen users reporting lower gain the causes are : 
 1) RF layout. Please EM simulate the RF traces. CPW traces are recommended. Ensure there is via fencing around the RF trace and RF pins with the via spacing of <1/4 the wavelength of the max RF frequency. 
 2) Solder coverage on the exposed paddle. Please check with the assembly vendor for X-Ray images and ensure coverage of >80% on the exposed paddle. 
 3) Startup procedure. Please follow the correct startup procedure. Make sure the SPI readbacks for each register is giving the expected value. 
 4) Lower voltage at IC supply pins. Please check the voltage on decoupling caps that they are what's expected. Please account for IR loss from the power solution to the IC. Also please make sure that the lowest value decoupling capacitor is as close as possible to its IC supply pin. Please refer to the ADMV1014 gerber files. 
 Thanks,)

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BG_RBIAS Resistor precision