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マザーボード EPC EPC9144のPDF クイック・スタート・マニュアルをオンラインで閲覧またはダウンロードできます。EPC EPC9144 9 ページ。 Development board for a 15 v high current pulsed laser diode driver

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QUICK START GUIDE

Figure 5 shows an example of an Excelitas SMD laser diode mounted

with one of the interposers.

Finally, a ground pad is made available for those who wish to use the

board for alternative applications.

The recommended procedure for the use of the interposer is the following:

1. Apply solder paste to the U2 pads on the EPC9144 PCB.

2. Apply solder paste to the appropriate pads on the top side of the

interposer.

3. Carefully place the desired interposer with the bottom side facing the

top side of the EPC9144 on the U2 footprint.

4. Place the laser diode or desired load on the interposer.

5. Reflow the entire assembly with the recommended temperature

profile for the solder used. The use of a reflow oven that can meet the

recommended soldering specifications is highly recommended. Other

reflow methods may also be used based on the experience of the user.

The power loop inductance, including that of the laser diode, is a primary

factor that determines the shape of the laser pulse. Considerable effort

has been made to minimize power loop inductance while maximizing

the choice of laser diode and its orientation. The discharge caps, laser

diode or other load, and the eGaN FET must all be mounted in close

proximity to minimize inductance. As a result, the user must take care not

to damage any components when mounting the laser or changing other

components in the power loop.

The EPC9144 is capable of driving laser diodes with current pulses

can result in peak powers of several tens of watts of optical power.

Laser diodes for lidar applications may be designed with this in mind, but

thermal limitations of the laser package mean that pulse widths, duty

cycles, and pulse repetition frequency limitations must be observed.

Read laser diode data sheets carefully and follow any manufacturers'

recommendations.

MEASUREMENT CONSIDERATIONS

MMCX jacks are provided to measure several voltages in the circuit,

including gate drive input, Q1 gate voltage, Q1 drain voltage, charge

voltage of the energy storage cap. All measurement points are designed

to be terminated in 50 Ω, hence when viewing waveforms, the

oscilloscope inputs should be set to a 50 Ω input. Ideally, unused inputs

should be also terminated with a 50 Ω load to prevent the probes from

creating additional resonances. The Q1 drain voltage and the discharge

cap sense voltage have on-board terminations to greatly reduce this

effect, and in practice, the remaining resonances are small enough to

ignore in most applications. It is recommended that the user verify this

for their own requirements.

All sense measurement MMCXs, except for the shunt measurement,

use the transmission line probe principle to obtain waveform fidelity at

sub-ns time scales. They have been verified to produce near-identical

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SMD lasers

MMCX

Left

Bottom

Figure 4: EPC9989 interposer. Note that this board is revised as needed to accommodate

new lasers and other loads as needed, so the picture may not show the latest revision.

eGaN FET

Current

shunt

Discharge

capacitors

EPC9126

Laser diode

or load

Figure 5: Laser diode mounting on output terminals with interposer

results to a Tektronix P9158 3 GHz transmission line probe. As a result

of their design, they have a built-in attenuation factor. The impedance

of the probes at the measurement node is relatively small (~1kΩ).

The user should keep this in mind if accustomed to more conventional

oscilloscope probes.

The current shunt J4 is not used at this time. A future revision may

include this functionality.

Table 2 summarizes the properties of the MMCX test points for ease

of reference.

Demonstration System EPC9144

Alternate loads

Gate driver

EPC9989

interposer

Breakaway

V-grooves

Recharging

resistors

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