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AFE030: RX only path used: What to do with unused pins?

AnBer
Mastermind 30170 points
Part Number: AFE030

Team,

Can you please help with the below questions.
Also can you please confirm for the RX only use case if it is acceptable not to apply power to PA_VS1/PA_VS2?

Since we will only need the RX path in the first step, some questions have arisen:
-If the 7-24V (PA_VS1) are omitted for the TX path, do various TX inputs, such as TX_PGA_IN, TX_F_IN(1/2), need to be pulled down to ground?
-Is it possible to pull these inputs directly to GND, or is a pulldown resistor needed?
-Are there any recommendations how to handle the resistor at PA_ISET?

Thanks in advance,

A.

  • +1
    TI__Guru* 77521 points

    Hi  AnBer,

    -If the 7-24V (PA_VS1) are omitted for the TX path, do various TX inputs, such as TX_PGA_IN, TX_F_IN(1/2), need to be pulled down to ground?

    -Is it possible to pull these inputs directly to GND, or is a pulldown resistor needed?

    There are two modes to configure Tx path, which are DAC and PWM modes. If AFE030 is powered on and left the DAC register unchanged (leave it as default setting), then you can leave these pins unconnected. This is likely your scenario. 

    If it is in DAC mode, then Tx_FIN1 and TX_FIN2 input must be grounded.  

    Please use the following configurations, since the above modes are bit confusing. 

    The ideas are to place the unused op amps inside of AFE030 in a linear operating region, where internal op amps are not operating in saturated mode. Since you do not need Tx path at all, you may leave all unused input Tx pins grounded per the input Vcm range specified in the datasheet (will not violate input Vcm range). Please also make Tx_PGA_IN = GND. 

    -Are there any recommendations how to handle the resistor at PA_ISET?

    You may connect the PA_ISET pin to ground, which AFE030's internal PA will source max. current of 1A. Since you ground the input, Please connect PA_IN = GND and the PA_OUT should be close to an offset voltage in mV, and leave the PA_OUT unconnected. The Power Amplifier is internally connected via feedback, which it has a fixed gain of 6.5V/V. 

    I hope that the configuration are easy to deal with. If you have any questions, please let me know. 

    BTW, the attached link is AFE031EVM module. It is the same as AFE030, pin to pin compatible, except it can source a slightly more current. Anyway, it may be easier if you do not have to put the circuit together, unless you already have one in place. 

    https://www.ti.com/lit/ug/sbou223/sbou223.pdf?ts=1645572479096&ref_url=https%253A%252F%252Fwww.google.com%252F

    Best,

    Raymond