AnsweredAssumed Answered

Help needed for HMC183QS24

Question asked by KeyZhu on Jun 13, 2015
Latest reply on Jun 17, 2015 by s.ilke

I had 2 HMC183QS24 used in a 8 channel switched filter bank. The 2 HMC183 are mirrored and the TLL inputs are synchronized by a CD74HCT04PWR (Hex inverter by Texas Instrument).

 

At first, the system works fine. However, the HMC183 suddenly fails as the 2 HMC183 switches are no longer synchronized (seems like the A B C pin of HMC183 is no longer controlling the channels as the original truth table) while the input voltage of A,B,C pin is correct. (The output of the Hex inverter is correct, and by theory the 2 HMC183 SHOULD be synchronized) The problem remains after changing the CD74HCT04PWR and all other components.

In addition to this situation, sometimes one or multiple channels would simply lose all reflections and S21 responses.

 

When HMC183 is replaced with new ICs, the system works fine, however sometimes the HMC 183 fail again. I have not able to identify the actual causes by now.

 

The system schematic and the system truth table is attached, The TTL input is lowered by a clamping circuit (from +5v~0v to 0v~-5V). the Hex inverter is powered by -5V through GND pin  to work with 0~-5v TTL signals. All DC power supplies are made by voltage-stabilized DC power source. All instruments and the filter bank are grounded. 

 

So the Questions are:

1, in what circumstance would some of the channels fail while others works fine in HMC183?

2, In what circumstance would the HMC183's Pin A,B,C fail to control the right channel?

3, are there any problem with the DC and TTL input circuits in my system?

4, what are the absolute maximum input voltage and current for Pin A,B,C of HMC183? Would low voltage cause this kind of problem?

 

I'm stuck with this problem for days, and lost 8 HMC183 chips for this problem. Help needed urgently, Thanks in advance!!

Attachments

Outcomes