I've purchased a TSL1406 Linear Sensor Array to read the position of a laser dot. The "Absolute Maximum Ratings" section in the datasheet specifies "Maximum light exposure at 638nm" as 5 mJ/cm^2. Being inexperienced with this sort of sensor, I would have expected a "max light" rating to be given in terms of something like mW/cm^2 and I'm not sure what to make of a mJ/cm^2 rating.

Q1: Does this mean that "something bad" will happen if the integration time multiplied by the mW/cm^2 of my laser dot exceeds 5 mJ/cm^2?

Q2: What is that "something bad"? Will the integrating capacitors fry? Or will they simply be unable to accumulate anymore, resulting in bad readings for that particular frame?


1 Answer 1


I think it's intended to be for pulsed laser conditions. Probably for pulse times short in comparison to the thermal time constant (which will be more than microseconds but much less than 1 second).

I would expect that relatively high energy pulses in excess of the maximum would permanently damage the chip in some way, maybe overvoltage failure of the capacitors or something else 'bad'.

  • \$\begingroup\$ Thanks for responding. So I probably don't need to worry about integration of a 1mW laser diode dot (say 1 cm^2) accidentally running several seconds and exceeding the 5mJ/cm^2 limit? I don't intend to integrate long enough to hit the limit -- I'm just curious how fragile the device is if I make a mistake. \$\endgroup\$
    – Bezewy
    Commented Jan 9, 2016 at 18:46
  • \$\begingroup\$ I sure don't think so, otherwise they would warn about solar exposure which is more than 100mW/cm^2. But you can certainly contact the manufacturer's tech support and see what they say. You can place the information here in an answer and you can then accept your own answer if it is better than my guesses! \$\endgroup\$ Commented Jan 9, 2016 at 19:20

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