Quick guide to GaN FETs for LiDAR in autonomous vehicles
coefficient (Δλ/ΔT) of 0.25 nm/°C. This quantum-well laser supports rise and fall times of <1 ns with an appropriate driver. The TPGAD1S09H can be used in surface-mount applications and hybrid integration. It can emit light parallel or perpendicular to the mounting plane, and the epoxy resin encapsulation supports low-cost and high-volume manufacturing. The SPL S1L90A_3 A01 from ams OSRAM (Figure 7) is another example of a laser diode that can be used with the EPC9989 interposer board. This single- channel 908 nm laser module can deliver pulses ranging from 1 to 100 ns with a peak output power of 120 watts. It supports an operating temperature range of -40 to +105°C with a duty cycle of 0.2% and comes in a compact QFN package measuring 2.0 x 2.3 x 0.69 mm. For LiDAR systems that require extremely narrow pulse widths, designers can turn to Texas Instruments’ LMG1025-Q1 , which is a single-channel, low-side gate driver with a 1.25 ns output pulse width capability that enables powerful LiDAR systems meeting IEC 60825-1 Class 1 safety requirements. Its narrow pulse width capability, fast switching, and 300 picoseconds (ps) pulse distortion enable precise LiDAR ToF measurements over a long range.
Figure 7: The SPL S1L90A_3 A01 laser diode produces pulses ranging from 1 to 100 ns and can be used with the EPC9989 interposer board. (Image source: ams OSRAM)
Figure 5: The EPC9989 interposer board provides a collection of interposers, such as the SMD laser interposer shown at the top right, that can be snapped off for use with the EPC9179 demo board. (Image source: EPC)
Figure 8: The LMG1025-Q1EVM demo board can accommodate a resistive load representing a typical laser diode for initial setup. (Image source: Texas Instruments)
The development board comes with an EPC9989 interposer board comprising break-away 5 x 5 mm interposers (Figure 5). These correspond to the mounting
A propagation delay of 2.9 ns improves the control loop response time, and the 2 x 2 mm QFN package minimizes parasitic inductance, supporting high- current, low-ringing switching in high-frequency LiDAR drive circuits. The LMG1025-Q1EVM is an evaluation module for the LMG1025-Q1 that has a place to accommodate a resistive load to represent a typical laser diode, or for mounting a laser diode after drive pulse tuning with a resistive load (Figure 8).
Conclusion
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footprints of many common surface-mount laser diodes, such as SMD and MMCX, as
Designers are increasingly challenged to develop automotive LiDAR systems that deliver real- time ToF measurements with centimeter resolution that meet the Class 1 safety requirements of IEC 60825-1. As shown, GaN FETs can be used with a variety of laser diodes to produce the nanosecond pulse widths and high peak-power levels needed in high-performance automotive LiDAR.
well as the patterns designed to accommodate RF connectors and a wide variety of other loads. Excelitas Technologies’ TPGAD1S09H pulsed laser (Figure 6), emitting at 905 nanometers (nm), can be used with the EPC9989 interposer board. This laser diode uses a multi-layer monolithic chip mounted on a leadless laminate carrier to provide excellent thermal performance with a wavelength temperature
Figure 6: The TPGAD1S09H pulsed laser produces very high peak pulses and can emit light parallel or perpendicular to the mounting plane. (Image source: Excelitas)
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