I am using the HMC980LP4E to power 4 TGA2598-SM on a single board.
The design is attached and it would very appreciate your review and recommendations.
Thanks a lot.
One of the main purpose of using HMC980 to bias and AMP is to continuously monitor Idd of the DUT and change Vgg accordingly. This will provide significant improvement to part to part and temperature variations for the DUT.
If you use 1x HMC980 for 4x DUT, you will loose that improvement over variations, since 4 of the DUTs will not be exactly same. One AMP will drain more current than the other etc.
That being said, the configuration you suggest can wtill be applicable.
According to the DS of DUT AMP, typical Idd is below 300 mA. For 4 devices Idd will be less than 1.2 A. The Idd value will be determined with the Rsense R?+R91 on the SCH you shared.
With the S1=HIGH, S0=LOW configruation you chose, the Rds_ON for HMC980 will be 0.85 ohms.
And the Vdd for HMc980 will be, Vdd=Vdrain + Idrain*0.85. So you may need to adjust the 16 V of HMC980`s Vdd accordingly, so that DUT AMP Vdd will be what you need.
Again, according to the DS of DUT AMP, the typical Vgg can reach 2.4 mA at specific freq and Pin conditions.
Keep in my that HMC980 can tyically sink/source up to 4 mA. So, you need to use DUT AMP under a conditions such that Igg should be less than 1 mA.
You plan to use external -3 V and the typical Vgate of the TGA2598-SM is -2.5 V.
You will need some external resistors to adjust the Vgate output of HMC980, such that Vgate can be lower than -2.5 V. When using external Vneg other than -2.5 V, I suggest to, at least leave those resistor places on the PCB. Refer to attached SCH for the values.
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