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RTOS/CC2538: CC2538 and OPA2365 Integration issue of interference

Part Number: CC2538
Other Parts Discussed in Thread: CC2592, OPA2365, , OPA365

Tool/software: TI-RTOS

Hello TI,

We are using CC2538 with CC2592 for Zigbee(RF) and as controller and OPA2365 amplifier to amplify the microwave sensor signal  (For reference i attach microwave sensor amplifier circuit schematic, please go through it)

CC2538 and CC2592 board work standalone properly and OPA2365 board work standalone properly 
when i source both circuit from common supply problem started, there is voltage spike generated in amplifier output which make system false trigger 

1.Output of OPA2365 coming to CC2538 interrupt pin
2.Supply source is common for both circuit  
3.By using OPA2365 interrupt detection we trigger the relay
4.we test the both circuit by supplying different source and make ground common only, that time also spike is present 

where is the issues cc2538 affecting amplifier circuit ..?
How to remove that spike which is generated when i make common ground of the both circuit 

Thanks,
Rahul surawase

  • What do you mean spike is present? Where do you see it?

  • Hello Yikai,

             We Observe the Output on Oscilloscope  


    OPA2365 work standalone properly with above mention circuit schematic, Input of the OPA2365 from CDM324 Microwace sensor IF signal 
    Controller(CC2538 and CC2592) work standalone properly with Zigbee 

    But when we integrate and try to provide OPA2365 Output to the CC2538 for further process
    when we just make the ground common to the OPA2365 and CC2538 there is problem started, there is some voltage spike come randomly in OPA2365 resultant output we observe this on Oscilloscope

    Please Provide so solid solution to remove this voltage spikes from OPA2365 Output which is generated because of CC2538Ground signal 

    1.Testing Circuit 

    2.Testing Results 
       a.without any Motion detection resultant output(Only Power to the OPA2365 board)

      b.Output with Motion detection results 

     C.which i want to remove voltage spike in amplifier Output 

      

    Thanks, 
    Rahul Surawase 

  • Hi Rahul,

    I do not see any capacitors between power and ground close to the OPA365. If there are none, any disturbance in the power supply could cause a large spike, since the power wires to the device are inductive, and they cannot supply current fast enough to settle errors very well. Therefore, a low ESL ceramic "bypass" capacitor is needed close to the device. Section 10 of the datasheet has more information.

    Best regards,

    Sean

  • Hello Sean, 

    There is Bypass capacitor between Power and ground, we use for that 0.1uf ceramic and 10uf electrolytic capacitor  
    we also use 2200uf electrolytic cap across Power and Ground 
    there is any other-way to resolve it, thanks for your valuable response 

    Thanks & Regards,
    Rahul Surawase

  • Can you send another picture? The 10uF needs to be ceramic because it electrolytic has high inductance, just like the power line.

  • Hello Sean,
        You think spike is generated because of Capacitors ....?
    We Observe this Voltage sipke when we try communicate with zigbee network (Sending and receive any command from wireless)
    when there is nothing system in ideal that time voltage spike generated every 15sec in avg on the Amplifier output, the problem in also even when we make common ground of the system 
    There is no issues in standalone 

    Thanks and Regards,
    Rahul Surawase