• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 48 subscribers
  • Views 303 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

Original question:

AMC3330: AMC3330 issue

AMC3330 Differential to single-ended

Hangjie Wang
Intellectual 1050 points
Part Number: AMC3330
Other Parts Discussed in Thread: TLV313, LM7705, , TLV313-Q1

Hi expert,

Could you help to check if VREF can be connected to GND?

  • 0
    Guru 140200 points

    Hi,

    it depends on how you power the TLV313 and how close the output of TLV313 shall go down to 0V. If the TLV313 is single supplied, then the output voltage of TLV313 cannot go closer to 0V than about 50mV. The speed performance is also degraded in that region. Applying an offset voltage to Vref will shift the output voltage of TLV313 by this offset voltage and the OPAmp can come close to this offset voltage without any degradation, provided the offset voltage is somewhat higher than 50mV, better about 100...200mV.

    When the OPAmp is powered with a bipolar supply, on the other hand, then the OPAmp may go all the way down to 0V at the output without any problems. And since the TLV313 is a rail-to-rail-OPAmp, a small negative supply voltage, eventually coming from a LM7705, will suffice. A small negative supply voltage helps to prevent issues at the input of ADC caused by all too negative going input voltages.

    Kai

  • 0 in reply to kai klaas69
    TI__Guru 51271 points

    Hi Hangjie,

    In addition to what Kai mentioned, without bipolar supplies or VREF above ground, the AMC3330-Q1 will not be able to measure from -1V to 0V as the single-ended output from the TLV313-Q1 will be clipped. 

    If the customer is OK with only using the positive input voltage swing of the AMC3330-Q1 and degraded performance near 0V, then it is possible. What voltage magnitude is the customer going to measure?