LTC1966 won't work

Hi Everybody , 

I soldered my LTC1966 on an MSOP to DIP adaptater to test it and see how it works .

So once i had it done i made the following connection, you can see the schematics in the image joint (all the grounds are connected) , my LTC1966 outputs a voltage of 600 mV once it is powered whatever the IN1 Value is .

I don't understand why this is happening.

Can you guys help me please if you know why it is happening or what can i do to debug this problem .



  • 0
    •  Analog Employees 
    on Jul 23, 2019 4:57 PM

    Hi MB:  The LTC1966 senses both DC and AC.   You have 1.5V DC on the input, in addition to the 3Vpp AC, so you are overdriving the input.  If you want an AC measurement, then you need to block DC.  See Figure 9 in the datasheet.

    But there are probably more issues as well, because the LTC1966 should be able to do more than 0.6V on its output.   See the plot "Output Accuracy versus Signal Amplitude" in the data sheet.

  • Thanks a lot for your response I see what you are pointing but I think my first message wasn't clear .

    The measurement that i want to do is for an AC+DC signal and before i do it on my real signal I am using a Low Frequency Generator so I can test my LTC1966 and calibrate it by making the different operations described in the datasheet to determin the gain error , the input and output offset .

    But the issue that i am facing is the LTC1966 outputs 0.6V when it is powered (VDD = 4V; VSS = GND)and without any signal on the input (IN1 = GND ; IN2 = GND) , and when I activate the output of my Low Frequency Generator (which generates a sinusoidal wave with the right amplitude and the right offset ; IN1 = [0V ; 3V] ,  IN2 = GND) the output doesn't change it remains 0.6V.

    It doesn't make sense for me can you guide me to do some manipulations to see if the LTC1966 is in "good shape" .

    Thanks a lot for your help .

  • 0
    •  Analog Employees 
    on Aug 2, 2019 9:14 PM in reply to MB_ENMSE

    How are you measuring the output?   And do you have a capacitor on the output?

  • 0
    •  Analog Employees 
    on Aug 2, 2019 9:19 PM in reply to MB_ENMSE

    Oh I see you are using an oscilloscope and do have an output cap.

    One thing I don't see is Pin 8.  Make sure you have the _En pin tied low.

  • Hi  thanks for your response this time I used a new LTC1966 that i had soldered by a professional on my MSOP adaptater and I used the exact same connection illustrated in the figure 9c of the Datasheet of the LTC1966 with a VDD of 5V and a sinusoidal signal that goes from 0V to 500 mV.

    A coupling capacitor of 0.1 uF from IN2 to GND and all the other pins are connected to GND .

    The GND of my signal generator and the lab alimentation are linked as you can see in the photo . 

    The problem is whatever the sinusoial signal of my input the output won't change and remains on the 0V .

    I am really stuck  I just got back to it .

  • Update : It is working now thank you , I just had to get the right parameters for my sinusoidal signal i forgot that I have 50 ohms on the output of my generator , and i had to remove the capacitance on the IN2 because i want the RMS measure of the whole signal (AC+DC)

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