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Query Regarding Talp1000b

Vishal Mehta
Intellectual 315 points
Other Parts Discussed in Thread: DAC7744, DAC7724, THS4222, OPA2830

Hello,

I am working on an application which requires the use of Talp1000b. I just want to know that what is the minimum value of voltage which we can give to the mirror in order to rotate it just by a step (a step may be 0.0001 degree). And also what is the maximum voltage that can given to it....???

Regards

  • 0
    TI__Prodigy 230 points

    Hi Vishal,

    The TALP1000B is an analog pointing mirror. It does not operate by moving in discrete angular steps. The voltage applied to the drive coils produces a current which results in mirror rotation. There is no minimum current increment for mirror rotation. If you are using a digital to analog current (voltage) drive then the step size of the digital command determines the minimum mirror rotation and is a system design parameter which can be optimized for your application.

    In addition to the digital drive command quantization, there are other factors that can limit the minimum resolvable mirror angle. Noise in the customer supplied drive supply will produce mirror motion. Any closed loop controller will have noise in the position sensor which will also produce mirror motion.

    The maximum voltage that can be safely applied to the mirror drive coils is 5 volts.

    Regards,

    Arthur

  • 0 in reply to Arthur Turner
    Intellectual 315 points

    Hello

    Thankyou for replying...Yes currently i am using 12 bit DAC 7724 i did test it and its working but my design needs to use a higher resolution DAC i. the application needs to use the detector output also..so a close loop system is to be made. I did found DAC7744 which 16 bit equivalent of the above so i asked regarding the minimum voltage requirement.

  • 0 in reply to Vishal Mehta
    Intellectual 315 points

    Sorry for continuing in this thread only but i had some queries regarding TALP1000b. I want to know the maximum power it can sustain as in if i use a 30mw laser it would it affect the mems mirror??? or do i have to use ND filters in order to reduce the power?

  • 0 in reply to Vishal Mehta
    Intellectual 315 points

    I got the answer from one of the threads saying 1 watt anyways thanks a lot.

  • 0 in reply to Vishal Mehta
    Intellectual 315 points

    Hello, Sorry for troubling again but i am having a problem with MEMS talp1000b..The thing is that i have connected the output of DAC7724 Vouta and Voutb with 1 and 11 pin, 2 and 12 of talp1000b with gnd. Vrefh and Vrefl of DAC7724 is  2.4 and -2.4 respectively . When i give 0xfff to DAC data bits it shows 2.4 volts at Vout a (A0 and A1 = 00) which is connected to pin 1 and pin2 is gnd so at the pin1 of Talp1000b it should show 2.4 but it shows 0.772 volts i can not figure it out where i am going wrong. Can you suggest a method to check whether the voltages coming on pin are right or wrong?

    Thanks

  • 0 in reply to Vishal Mehta
    TI__Prodigy 230 points

    Greetings Vishal,

    The DAC7724 data sheet lists the maximum analog output current at 5mA. The TALP1000B requires up to 65mA of current to operate the mirror to full angle. The coil drive resistance of the TALP1000B is specified at 66 +/- 5 ohm. If 2.4V are placed across a 66 ohm load the resultant current should be 36.9mA which far surpasses the current capacity of the DAC7724 and is pulling the output voltage down. To check the voltages coming out of the DAC you can disconnect the DAC from the mirror and measure the pin voltage as a function of commanded value. Reconnect the DAC and remeasure to verify that the current is limiting the voltage output (this should happen at about 0.4V commanded DAC output which will pull over 6mA). You will need a higher output current DAC to drive the TALP1000B to its full operation angles.

    Regard,

    Arthur Turner

  • 0 in reply to Arthur Turner
    Intellectual 315 points

    Hello Arthur thanks for quick reply...Can you suggest a 12 bit DAC with minimum 2 channels to drive Talp1000b at its full operational angles??

    Yes you are right about the DAC pulling the voltage down I should have thought about this  :(

  • 0 in reply to Vishal Mehta
    TI__Prodigy 230 points

    Greetings Vishal,

     

    Two possibilities are:

    1. The THS4222 DAC is capable of supplying up to 100mA.
    2. The OPA2830 is also a candidate. However, the specs in the OPA2830 datasheet show that it will work but it does not cover the entire range of the TALP1000B current drive (65mA). It can output 63mA at 25C, which would probably be enough for a slow moving system, but that drops off to only 53mA over the entire temp range of the device.

    Regards,

    Arthur Turner

  • 0 in reply to Vishal Mehta
    TI__Prodigy 145 points

    Hello Vishal,

    I just want to make sure you are aware the TALP1000B device is classified as NRND status (not recommended for new designs).  This basically means we are not moving forward on any new developments in the Analog Mirror space.  

    If you have any questions about this, please give me a call.

    Best regards,

    Joe Siddall
    214-567-6475

  • 0 in reply to Bosun
    Intellectual 315 points

    Hello Joe,

    Yes i know about this but I already have been working with this since few months now and I do not know if there is any alternative to Talp1000b. If you can suggest some other alternatives i would be glad...

  • 0 in reply to Arthur Turner
    Intellectual 315 points

    Thanks a lot i will see the alternatives....

    Can I use buffer after DAC ouput to amplify the current keeping the voltage same???