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.

LMP8603: How to calibrate Voffset on Reduce Gain condition

Guru 18070 points
Part Number: LMP8603
Other Parts Discussed in Thread: LMP8601

Please let me know about idea for fixed Voffset on Reduce Gain condition, detailed information is below.

----------------------------------------

・Vs: 5V and Voffset: 2.5V

・On datasheet page-23, Rr is using digital potentiometer and adjust Gain. 

  But when Rr value (= Gain) is change, A2 input voltage also decrease, as a result LMP8603 can not output less than Voffset. 

・If change Rr to Capacitor, Vs/2 output was clear but higher Gain for customer request. 

・If change LMP8603 to LMP8601 and Increase Gain condition, maybe clear but occur layout change.

----------------------------------------

If there any idea for constant output referenced Vs/2, it is great helpful.

Best regards,

Satoshi

  • Hello Satoshi,

    We are looking into your issue now and will get back to you shortly.
  • Satoshi,

    The configuration on page 23 of the datasheet (also shown below) is for reducing the gain.  The default gain of the LMP8603 is 100V/V.  Any resistor tied to A1, A2, and ground like in the figure below, will lower the voltage at A2 and the overall gain of the LMP8603 device.  Below is a table that summarizes the gain trend with respect to Rr.  As for the output going less than the Voffset,  I suspect that your issue is you only have positive current flow across your shunt.  However, could you share a diagram of your circuit and the expected current conditions?  Also, what do you mean your output was 'clear' with capacitor?

    Figure 1

    Table 1

  • Hello Satoshi,

    I have not heard from you in a while. I presume your issue has been resolved. However if you do have any further questions, feel free to ask here or if it is about a different device in a new thread.