HMC1120 dynamic range @ 3.9GHz

Hello brantchen, 

There are slight differences between the two curves, as you point out. It's possible that the data source for each graph is from different ICs or different PCBs. 

Please understand that these graphs are typical performance. Actual performance varies from part-to-part.   -Bruce H. 

Hi Bruce:

Thank you for the reply. May you please advise below questions.

1. If we turn off ETOUT, how to connect pin7? floating or 604 ohm termination? Pin8 is NC?

2. Is Pin14 for adjust rmsout level?

3. In DS p20. if operating at lower SCI, is there suggested part of amplifier/buffer?

Thanks!

Greetings brantchen,

1. If not using ETOUT, normally we would advise leaving the output open. However, in this case, because of the simplified circuit for this pin showing as emitter follower on page 12, the safe-harbor solution is to use 604 Ohm external load resistor to ground, as shown on the EVB schematic, R41. This helps ensure the internal circuitry stays biased as originally intended. 

2. HMC1120 supports either Controller mode, or Measurement mode. In Controller mode, RMSOUT pin would control the gain of an external VGA or driver amp, and VSET pin should be connected to a DAC output. The DAC then sets a voltage proportional to RMS power in dBm. Alternatively, in Measurement mode, RMSOUT pin feeds directly back to VSET pin through a nearby voltage divider, as shown in eval board schematic. Evaluating HMC1120 performance is most commonly performed in Measurement mode, but Controller mode is available for systems where HMC1120 is part of a power leveling loop, and external component count is to be minimized.

3. It's common to use an external output buffer amplifier, especially if driving long cables or lower input impedances, or highly capacitive loads. Look for an amplifier that provides more output current than the +/- 8mA that HMC1120 typically provides. Also, the buffer amp output should slew faster than the HMC1120 RMSOUT, which is 10V/us. Also make sure the amplifier output can swing from <0.2V to >2.8V, to match HMC1120 RMSOUT voltage range. See for example the AD8029 or AD8031. If driving ADC with differential input, then a differential input/output buffer amplifier would be appropriate.   -Bruce H. 

Greetings brantchen,

1. If not using ETOUT, normally we would advise leaving the output open. However, in this case, because of the simplified circuit for this pin showing as emitter follower on page 12, the safe-harbor solution is to use 604 Ohm external load resistor to ground, as shown on the EVB schematic, R41. This helps ensure the internal circuitry stays biased as originally intended. 

2. HMC1120 supports either Controller mode, or Measurement mode. In Controller mode, RMSOUT pin would control the gain of an external VGA or driver amp, and VSET pin should be connected to a DAC output. The DAC then sets a voltage proportional to RMS power in dBm. Alternatively, in Measurement mode, RMSOUT pin feeds directly back to VSET pin through a nearby voltage divider, as shown in eval board schematic. Evaluating HMC1120 performance is most commonly performed in Measurement mode, but Controller mode is available for systems where HMC1120 is part of a power leveling loop, and external component count is to be minimized.

3. It's common to use an external output buffer amplifier, especially if driving long cables or lower input impedances, or highly capacitive loads. Look for an amplifier that provides more output current than the +/- 8mA that HMC1120 typically provides. Also, the buffer amp output should slew faster than the HMC1120 RMSOUT, which is 10V/us. Also make sure the amplifier output can swing from <0.2V to >2.8V, to match HMC1120 RMSOUT voltage range. See for example the AD8029 or AD8031. If driving ADC with differential input, then a differential input/output buffer amplifier would be appropriate.   -Bruce H. 

Really appreciate your prompt reply!

I have one more question. About the COFS (pin9, 10), how to calculate the values of R48,R3 and C6, if my RF application range is 2.9G~3.3GHz.

Thanks!

Hello brantchen,

The resistors are normally both 0 Ohms, always. On dedicated PCB, no place holder for resistor is necessary. 

The capacitor value determines the effective high-pass corner frequency for the DC offset cancellation circuitry on-chip. See datasheet page 23, section 1.7. There you will see a table of capacitor values. Notice that the EVB value of 1nF gives corner frequency of 220kHz, which means detector should have good response down to around 1 to 2 MHz.   Note: For best accuracy, the offset cancellation loop corner frequency should extend below the actual lowest frequency of operation, which is 2.9GHz in this case.  -Bruce H. 

Hello Bruce:

1. As DS mentioned, pin 8 is mode selection for ETOUT, if we don't use ETOUT, how should we set pin 8? (floating?)

2. How should we set pin 6 if we don't use PH_CAP? (floating/pull low?)

3. About pin9 and pin10, how to calculate C6 value for 2.9GHz? Is there any formula to come out the result of "Table 4. Loop Bandwidth for DC Cancellation"?

Thanks!

Hello Bruce:

Could you please advise below questions for us to apply in schematic, thanks!

Hello brantchen,

1. Logic level at pin 8 doesn't matter if ET output not used. Choose either GND or Vcc. Do not float. 

2. It's OK to not connect any external capacitor if this function is not used. In other words, leave open. 

3. Already discussed above. DS Table 4 shows the options. For 2.9GHz, C6 can be 0.1nF.

Hope that helps.  -Bruce H.