Other Parts Discussed in Thread: LMG1020,
According to TIDA-01573 app note, in order to really benefit from the high speed capability of the LMG1020 driver, separation of signal ground and power ground is recommended. So the source Kelvin pad of the GaN FET is connected to the signal GND while the other source pads are connected to the power GND. This way the two grounds are only connected together inside the FET.
My question refers to how to assign grounds for the following laser driver daughter card that plugs onto a motherboard:
Input voltage is 12V coming via a connector from the motherboard.
On the laser daughter card there are:
LDO providing 5V for the LMG1020 and also for some digital circuitry that shape the pulse for LMG1020.
Boost converter providing high voltage for the capacitor bank.
GaN FET and adjacent circuitry (capacitor bank, laser diode, clamping diodes, current sense resistors).
Following the app note recommendation it seems the power GND needs to connect to the source of the GaN FET and the GND nodes of the boost converter while all other GND nodes connect to the signal GND.
The connector for the 12V from the mother board has only one pin for GND. Which GND should this pin be tied to: signal or power GND?
Please advise.
Thank you,
Michael