AMC7908: How to control 4 IDQ currents with 2 sensors

Ryan Guerra

Part Number: AMC7908

Tool/software:

I am looking at the sequencing requirements of the A5M36TG240 and am interested in the TI AMC7908 Bias Controller. If I am understanding correctly, the AMC7908 would be a good bias controller for a single PA with 4 transistors even though 6 transistors are shown in the example. What I am still confused about is how IDQP2 can be untangled from IDQC2 when the two are tied together and measured by a single sense resistor. Do I just apply the current setpoints to IDQ2? Can I infer some split between IDQP2 and IDQC2?

2 months ago

+1 Erin Bowrie 2 months ago

TI__Genius 10280 points

Hi Ryan,

The AMC7908 can only actively monitor 2 drain currents. In this case, you'll want to monitor the 2 higher currents in the system and use additional current sensors for the remaining two. The application figure assumes the exact current of each PA isn't necessary to be known and is just monitoring for over-current situations.

Thanks,
Erin

0 Ryan Guerra 2 months ago in reply to Erin Bowrie

Prodigy 65 points

Hi Erin, is there a single or multi channel ADC that you would recommend for measuring the additional drain currents?

+1 Erin Bowrie 2 months ago in reply to Ryan Guerra

TI__Genius 10280 points

Hi Ryan,

This is something you may want to ask the INA team - TI has many current-sense amplifiers that would fit your needs.

Current-sense amplifiers product selection | TI.com

The INA4230 data sheet, product information and support | TI.com may be a good fit, it has 4 current sense inputs. An example application could use one of these for each PA and just use the AMC7908's ADC as a general monitor for PA protection. The actual team may have more suitable recommendations, though.

Thanks,
Erin

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AMC7908: How to control 4 IDQ currents with 2 sensors