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TLV2422: TLV2422 Drift　problem

TOSHIKAZU KATOU
Prodigy 10 points
Part Number: TLV2422

Tool/software:

We have configured a temperature amplifier circuit on a PCB using the TLV2422, and a Bluetooth module is also mounted on the same board. We have configured a differential amplifier with Gain=30, but we are experiencing a phenomenon where the amplifier output voltage drifts by approximately 40mV.

This issue does not necessarily reproduce consistently with the Bluetooth module's ON/OFF operation, but we would like to know if there have been any past failures or causes and countermeasures related to EMI with the TLV2422.

  • 0
    TI__Guru* 77501 points

    Hi Katou-san, 

    TOSHIKAZU KATOU said:
    configured a differential amplifier with Gain=30, but we are experiencing a phenomenon where the amplifier output voltage drifts by approximately 40mV.

    I have not experienced this particular issues over years, but it is possible. I found one old query that is related to the RF-immunity question, see the thread below. 

    https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/93788/rf-immunity-problems-tlv2422?tisearch=e2e-sitesearch&keymatch=TLV2422#

    Please make sure that decoupled couplers are used next to the TLV2422's supply rails. The feedback resistors in the differential amplifier are matching (gain = 30V/V with 0.1% resistor matching), where the common mode signal Radiated energy may be converted to differential signal and showed up at the op amp's output.  

    The radiated energy may be coupled via power supply due to poor power supply decoupling, it can be coupled via the input terminals or PCB traces (power or GND planes) connected to op amp's input etc.. If the TLV2422 does not have adequate LPF filter, the radiated energy from Bluetooth (2.4GHz) can reach and enter the op amp's input pins. It is difficult to say what the issues are. I may have to take a look at the schematic first.    

    If you have other questions, please let us know. 

    Best,

    Raymond