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HMC545AE is not working as switch!

Category: Hardware

According to the HMC545AE HF-Switch datasheet the logic outputs A and B switch the HF signal from pin 5 (RFC) to RF2 or RF1.

However, if I use a similar test layout as in the Eval-kit I am seeing the input signal an BOTH outputs (RF1 and RF2) regardless of control signals.

I am using A=+5V and B=0V as control signals.

I bought the parts via Mouser and I triple checked the pin assignment / datasheet and so on.

How is this  possible? I expect "RF1 and RF2 are reflective shorts when “Off” and no signal propagation on the side, that is OFF.

Top Replies

  • However, I am confused that you input 1Vpp signal from RFC, and you detected same 1Vpp signal from both RF1 and RF2?

    Yes, that is also my problem. Maybe I had a ESD problem with the production…

  • Anyway, I will retest the minimal setup, as soon as the new parts have arrived

    I retested the minimal setup with the new parts and now, everything works as expected with only one of the…

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  • Hi,

    With A=+5V and B=0V as control signals, you should expect RFC to RF1 on and RFC to RF2 off. How did you supply the control signals, using TTL driver as recommended in the datasheet? What would be the current value for both control signals? This will help understand if the digital circuit is functioning properly.

    Moreover, what is the RF input power and frequency? You said "I am seeing the input signal an BOTH outputs (RF1 and RF2) regardless of control signals". Then how much is your RF output power?

  • Thank you for your reply.

    How did you supply the control signals, using TTL driver as recommended in the datasheet?

    yes and no. In the productive circuitry I am using TTL drivers, as recommended and in the test circuit I have 0Ohm to +5V and GND.

    What would be the current value for both control signals?

    I can't say but there was no notable current draw, so below 1mA.

    what is the RF input power and frequency?

    I used a 20kHz Sinus signal with 1Vpp (50Ohm Output) as input and on the outputs, the same 1V signal was present, on both outputs.

    I have ordered a some new ICs and will retest the setup.

  • Your control signal circuitry looks good to me, and the current also looks OK.

    However, I am confused that you input 1Vpp signal from RFC, and you detected same 1Vpp signal from both RF1 and RF2? The switch is passive but you actually doubled the signal based on your description. I am not quite sure if I understand your situation. Did you use scope to measure output? Did you select AC 50Ohm instead of DC 1MOhm?

  • However, I am confused that you input 1Vpp signal from RFC, and you detected same 1Vpp signal from both RF1 and RF2?

    Yes, that is also my problem. Maybe I had a ESD problem with the production circuit because a HMC472ALP4E before a HMC545A was also defect (shorting out the power supply). However, the test circuit of a single HMC545A behaves the same...

    The switch is passive but you actually doubled the signal based on your description. I am not quite sure if I understand your situation.

    Well, than I was not clear enough. In the test circuit, the input signal from the function generator was in 50Ohm output mode, but RF1 and RF2 are not 50Ohm terminated and I am measuring with a scope (DC coupled, high impedance). I can't say anything about the signal power.

    I also think I misunderstood the sentence in the general description of the datasheet: " .... performance, ideal for filter and receiver switching. RF1 and RF2 are reflective shorts when “Off”. The two control voltages ...."
    I thought the second pair of switches to GND is just not drawn in the functional diagram, but maybe they are not there after all and the HMC545A is not the correct part for me.

    Anyway, I will retest the minimal setup, as soon as the new parts have arrived and with proper 50Ohm termination.

Reply
  • However, I am confused that you input 1Vpp signal from RFC, and you detected same 1Vpp signal from both RF1 and RF2?

    Yes, that is also my problem. Maybe I had a ESD problem with the production circuit because a HMC472ALP4E before a HMC545A was also defect (shorting out the power supply). However, the test circuit of a single HMC545A behaves the same...

    The switch is passive but you actually doubled the signal based on your description. I am not quite sure if I understand your situation.

    Well, than I was not clear enough. In the test circuit, the input signal from the function generator was in 50Ohm output mode, but RF1 and RF2 are not 50Ohm terminated and I am measuring with a scope (DC coupled, high impedance). I can't say anything about the signal power.

    I also think I misunderstood the sentence in the general description of the datasheet: " .... performance, ideal for filter and receiver switching. RF1 and RF2 are reflective shorts when “Off”. The two control voltages ...."
    I thought the second pair of switches to GND is just not drawn in the functional diagram, but maybe they are not there after all and the HMC545A is not the correct part for me.

    Anyway, I will retest the minimal setup, as soon as the new parts have arrived and with proper 50Ohm termination.

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