• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 226 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMH13000: Operating limits for pulsed laser drive

Mehdi B.
Prodigy 25 points

Part Number: LMH13000

Dear TI E2E team,

We are currently evaluating the LMH13000 to drive a laser diode and would like to clarify a few points regarding its operating limits.

Our laser operates at 5V and requires approximately 1.3A when active. The intended operating conditions are 10 Hz with a duty cycle between 20% and 30%, corresponding to pulse widths of roughly 20–30 ms.

Assuming the device is used in Mode 1 (high current mode), we would like to better understand the safe operating limits for this type of pulsed load.

More specifically, could you please advise on:

the minimum recommended switching frequency, and

the maximum allowable duty cycle

when delivering around 1.3A peak current in pulsed operation?

According to the datasheet, the device is specified for 1 A continuous current and up to 5A pulsed current, but it is not entirely clear how these limits translate into lower-frequency pulses with relatively long pulse widths such as in our case.

Any guidance on whether our intended operating conditions would be within the safe operating area of the device would be greatly appreciated.

Best regards,

  • 0
    TI__Expert 4040 points

    Hi Mehdi,

    The intended operating condition of 1.3A and 20-30ms of on time at 10Hz should be fine just make sure to keep the VLD as low as possible to reduce the power dissipated from the device and to prevent it from unnecessary heating. You can refer to equation 7 on page 21 of the datasheet to calculate the minimum VLD which is need for proper operation.

    The minimum switching frequency or the max allowable duty cycle depends on the power dissipation from the device and it can be improved by optimising the PCB layout for better heat dissipation from device to other cooler board areas. This can be achieved by putting thermal plane and vias on the PCB. 

    You can look at figure 5-28 of the datasheet plot which specifies how fast the die temperature rises for specific power dissipation from the device. Please note, that the device has a thermal shutdown feature which power down the device as soon as the die temperature reaches 160C.

    Regards

    Anant