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One Case Study For GSM Unstable Output Power Issue

criterion123
criterion123

The GSM power was unstable regardless of the power control level setting. After checking the schematics, the team found a 100 ohm resistor in the MIPI clock line that was distorting the clock waveform. This clock distortion was causing errors in decoding MIPI commands, resulting in the unstable power. Replacing the 100 ohm resistor with a 0 ohm resistor solved the issue by restoring the proper clock waveform.

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Symptom As shown below, the GSM power is unstable regardless of PCL. 2
Debug At first, we suspected the issue is due to unstable supply voltage and injected voltage into transceiver and PA from external power supply, but still failed. PATransceiver Power Supply 3
Debug After checking schematics, there is one 100 Ohm series resistor in MIPI CLK, which destroys CLK waveform. 4
Conclusion Due to CLK waveform distortion, there is MIPI command decoding error, which leads to this issue. After replacing the 100 Ohm resistor with 0 ohm resistor, and the issue is solved. 5

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One Case Study For GSM Unstable Output Power Issue

  • 1. 1
  • 2. Symptom As shown below, the GSM power is unstable regardless of PCL. 2
  • 3. Debug At first, we suspected the issue is due to unstable supply voltage and injected voltage into transceiver and PA from external power supply, but still failed. PATransceiver Power Supply 3
  • 4. Debug After checking schematics, there is one 100 Ohm series resistor in MIPI CLK, which destroys CLK waveform. 4
  • 5. Conclusion Due to CLK waveform distortion, there is MIPI command decoding error, which leads to this issue. After replacing the 100 Ohm resistor with 0 ohm resistor, and the issue is solved. 5