ADN8810 - Flicker Noise

The ADN8810 is a laser driver for low noise lasers. I'm missing information about noise.

For a laser driver that is used to drive a current for a certain set point a noise figure from DC to BW should be available.

Or flicker noise influence from DC to the frequency where the noise floor dominates should be pointed outsomehow.

I'm missing this totally in the datasheet.

Could someone from ADI please provide this relevant information - thx !!!

  • Dear Tbet2017,

    ADN8810 works as one programmable current source to an attached laser diode.

    ADN8810 uses one 4.096V voltage reference input and an internal 12- bit DAC to control its output current.

    If a full scale output current is set to 300mA, each LSB would correspond to 73.2uA output current.

    Noise Performance:

    At variety full scale currents, datasheet specified current noise density @ 10kHz: 7.5nA/SQRT(Hz), 3nA/SQRT(Hz), and 1.5nA/SQRT(Hz), respectively. ADN8810 bandwidth could be upto 5MHz.

    ADN8810 is guaranteed with +/- 4 LSB integral nonlinearity INL and +/- 0.75 LSB differential nonlinearity DNL.

    ADN8810 device noise, such flicker noise, is not specified in the ADN8810 datasheet,

    however, its impact is included in the INL and DNL.

    To approach a low noise performance, ADN8810 should work with low noise AVDD, DVAA, PVDD, and Vref.

    For your application, what is your target optical noise performance expectation?

    Best Regards,

    Dongfeng

  • Hmm, this would mean for I can expect a cumulated noise (from DC to 5MHz - including flicker noise) below +/-0.75 LSB for  the LSB, right - that means about 110uA pk-pk - realy ?

    Is this rule btw. just true for a max current of 300mA or still true for instance for a current limited to 50mA ?

    What is valid if I use the ADN8810 for a max current of 10mA or even 1mA ?

    If this shouldn't be valid for 1mA for instance over a bandwidth from DC to 5MHz  - what would be the value (probably dominated by flicker noise) for a bandwidth of ,DC to 1Hz/10Hz.

    Best, Thorsten

  • Dear Tbet2017,

    ADN8810 specification table covering Iout from 2% Ifs to 100% Ifs.

    At variety Ifs, the current noise density @ 10kHz:

    Ifs = 250mA:   7.5 nA/SQRT(Hz);

    Ifs = 100mA:   3 nA/SQRT(Hz); and

    Ifs = 50mA:   1.5nA/SQRT(Hz).

    For example, if you define the max. Iout = Ifs = 50mA, and you just program ADN8810 Iout = Ifs * 2% = 50 *0.02 = 1mA,

    You would see ADN8810 noise performance is still in the range of +/- 4 LSB INL and +/-0.75 LSB DNL.

    When set Ifs = 50mA, each LSB = 50mA / 4096 ~ 12.2 uA. 0.75 LSB --> 12.2uA * 0.75 = 9.15uA.

    The cumulated noise (assumed rms white) could be: SQRT(5MHz) * 1.5nA/SQRT(Hz) = 3.35uA.

    Where is the 110uA p-p coming from?

    Best Regards,

    Dongfeng

  • Is this 9.15uA p-p noise or rms ?

    mentioned here :

    When set Ifs = 50mA, each LSB = 50mA / 4096 ~ 12.2 uA. 0.75 LSB --> 12.2uA * 0.75 = 9.15uA.

  • 0
    •  Analog Employees 
    on Aug 2, 2018 3:44 PM over 2 years ago
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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