cedricc

Common supply of 3x HMC981 controllers

Discussion created by cedricc on Oct 26, 2016
Latest reply on Oct 26, 2016 by cedricc

Dear all,

I experience troubles while using HMC981 bias controllers.

 

Here is background:

The aim is to bias 2 MMICs (OMMIC CGY2128 + ALH476). But I would like to manage 3 stages, so I am using 3 IC controllers:

>>> IC12 is for 2 first stages of CGY2128 MMIC. Drain current is about 2x12mA=24mA with +3.5V drain voltage. Typical gate voltage is around -0.4V.

>>> IC3 is for 3rd stage of CGY2128 MMIC. Drain current is 25mA with +3.5V drain voltage. Typical gate voltage is around -0.3V.

>>> IC4 is for ALH476 MMIC. As I am looking for more gain, the drain curent is increased up to 150mA with +4V drain voltage. Typical gate voltage is around 0V.

 

The input voltage is a single regulated +5V I share between the Vdd and Vdig of the controllers. I attach a schematic of the demoboard. With some jumpers I am able to configure the supply of controllers: just some of them or all of them.

 

Up to now, the controllers are just enbaled with EN connected to Vdd=Vdig. I do not manage the triggering, but the option will be put in motion.

 

I would like to share the -1V VNEG from a master controller to the 2 others (with jumpers also). But for now each controller is able to generate its own -1V.

 

The problem is:

Supplied independanlty, all the controllers work fine. Each controller is able to supply the right bias.

Supplied all together the controllers 12 and 3 do not work properly or are not enabled. The gate voltage is stuck to -1V and drain voltage is at 0V. Only the IC4 works well and generate the right gate/drain voltages.

 

My question:

Regarding the controller supply: am I allowed to share a common +5V for Vdd and Vdig or shall I carefully decorrelate these supplies. Like a main +5V for Vdd and a 2nd +3.3V for Vdig?

Is there a special load regulation or a buffer circuit to set between regulator and controllers to avoid issues? But the tracks are carefully decoupled as specified by the linear regulator and the controllers.

 

Please let me know your feedback about this. I am running out of solutions. Thanks in advance.

 

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 Cedric

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