We are bringing up a board based on the NXP Volansys Modular Gateway Reference Design. We are setting 5.2V on the power supply to achieve 5.0V on the J15 connector.
The current drawn by the board (as shown by the power supply) is almost 1.5A.
The measuremets results are:
- voltage on the R22_LTC2 - 4.29V (should be 5V)
* TP3 (VSYS_5V) - 3.49V (Reference Design Value: 5V)
* R141 (SYS_5V) - 3.6V (Reference Design Value: 5V)
* TP20 (VSYS_5V) - 3.45V (Reference Design Value: 5V)
* R147 (VSYS_5V) - 3.44V (Reference Design Value: 5V)
* TP21 (VCC_3V3) - 0.14V (Reference Design Value: 3.3V)
* TP22 (VDD_3V3) - 0.14V (Reference Design Value:3.3V)
What could be causing the voltage drop between the reference design value and the measured value?
Thanks for sharing the test data.
Based on your testing it shows that impedance between 3.3V and GND is <1 ohm (low impedance). It means that the board power is short. And due to that, the complete power rails are getting off/dropdown. Kindly remove L7 and check the which side the 3.3V is getting low impedance with GND. DC-DC Buck side or System load end.
Please check the below data and let us know your findings.