Pulsed Laser Diode Circuit Design

flux

The Flux library has a suitable GaN driver, but I didn’t find a small discrete GaN FET part entry; I’ll use a clearly-labeled placeholder switch in the schematic so the topology is complete, and flag it for replacement with the exact EPC/Infineon/TI GaN FET once you choose the MPN.

flux

Components are added, including SMU and 5 V supply connectors; I’m wiring the laser path, dummy path, complementary gates, and local bypassing now.

flux

Created the dual current-steering schematic in the project and renamed it GaN Laser Pulse Driver. The schematic includes the SMU current input, laser branch, dummy branch, sense resistors, SMA pulse input, STDRIVEG600 gate driver, 5 V driver input, decoupling, and ERC review was clean after fixing U1:PVCC.
Open items:
  • Q1 and Q2 are clearly labeled placeholders because the Flux library did not contain a suitable small discrete GaN FET.
  • Exact GaN FET MPN and final driver pin usage still need datasheet confirmation before layout.
  • Your account has no available ACUs, so I cannot continue with more tool-based edits right now.
Created project files:
Find GaN FETs
Verify driver pins
Run ERC/DRC
Update design notes
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Laser Driver Design Notes
Requirements
  • Laser diode forward voltage: 1.4 V
  • Peak laser current: 100 mA
  • Pulse width: >=10 ns
  • Rise/fall time target: R2 dummy load -> Q2 -> RS2 -> GND`
  • Laser pulse path: SMU_CURRENT_NODE -> LD1 -> R1 damping -> Q1 -> RS1 -> GND
  • Q1 and Q2 are complementary low-side switch positions.
Key Design Decisions
  • The SMU must not be asked to generate the nanosecond pulse. It supplies continuous 100 mA DC.
  • The dummy branch approximates the laser diode operating voltage so the SMU compliance voltage changes minimally between pulse states.
  • R2 = 14 ohm gives about 1.4 V at 100 mA, matching the user's laser diode Vf.
  • RS1 = RS2 = 1 ohm gives about 100 mV at 100 mA for oscilloscope current monitoring.
  • R1 = 5 ohm is an initial damping/ballast value and should be tuned experimentally.
  • RT1 = 50 ohm terminates the SMA pulse input.
Important Placeholder
The Flux library did not contain a suitable small discrete e-mode GaN FET entry. Q1 and Q2 currently use a clearly-labeled MOSFET placeholder and must be replaced by the selected GaN FET MPN before layout/manufacture.
Open Engineering Items
  • Select exact GaN FET MPN and verify gate voltage, package, pinout, Qg/Coss, and thermal limits.
  • Confirm STDRIVEG600 low-side output pin usage against the selected GaN driver application circuit.
  • Add an inverter or complementary pulse source if the external pulse generator cannot provide non-overlapping complementary drive.
  • Validate pulse shape with high-bandwidth probing at RS1 and RS2.
  • Layout must keep LD1, R1, Q1, RS1, Q2, R2, RS2, and C1 in an extremely compact loop.

    Requirements

    Architecture

    Key Design Decisions

    Important Placeholder

    Open Engineering Items

Documents

    Laser Driver Design Notes

    Board Bring-Up Plan — GaN Laser Pulse Driver

Assets

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GaN Laser Pulse Driver

GaN Laser Pulse Driver thumbnail
Dual GaN current-steering pulsed laser diode driver using a PXIe SMU as a continuous 100 mA current source, targeting >=10 ns pulse width and <10 ns edges.

Properties

Properties describe core aspects of the project.

Pricing & Availability

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