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Original question:

TPS65219: PMIC has no output for TPS65219

TPS65219: TPS6521904RSMR: No Output or GPO2 Activity After Cold Start

George Zhang
Prodigy 70 points
Part Number: TPS65219
Other Parts Discussed in Thread: AM623

Tool/software:

Hello Experts,

Our custom board has the TPS6521904RSMR part number to handle power delivery for AM623 CPU and DDR4 memory. 

VSYS is 3.8V. LDO1 and LDO2 are unused. PIN25 EN/PB/VSENSE is pulled up to VSYS. GPO2 is also pulled up to VSYS. We uses the PROC142A1(002) schematic as a reference so the rest pretty much just match the EVAL board design. 

After a cold start, VSYS stays stable at 3V8. However there is no output from any buck or LDO. No activity on GPO2(First event in the power-up sequence).

The footprint (pad, mask, paste) matches the recommended land pattern in the datasheet - We can verify this again by removing the component but would like to hear your option first.

We also read all the registers and everything seemed to be normal, please see register values below. FSD is enable as it should. It does indicate some residual voltage on Buck2 (1V8). We suspect that it comes from the I2C hack - Not sure if it reads the FB pin in real time but the rail itself stays low without the external I2C access when VSYS is fed. 

0x2b:0x82
0x2c:0x00
0x2d:0x00
0x2e:0x00
0x2f:0x00
0x30:0x00
0x31:0x02
0x32:0x00

Any idea or suggestion would be appreciated and let me know if you need more information.

Thank you

George

  • +1
    TI__Expert 6255 points

    Hi George,

    Thank you for reaching out on e2e.

    Thank You for using E2E. The TPS65219x PMIC executes two residual voltage (RV) checks. The first one occurs before the start of the power-up sequence and the second one occurs during the power-up sequence (right before each rail is turned ON). If any of the PMIC rails has a residual voltage above the SCG threshold, PMIC tries to discharge the voltage but in some cases it is not a residual voltage but instead a backfeeding voltage that is actively being forced at the PMIC output. If the PMIC is not able to discharge the residual voltage, it aborts the sequencing.

    In your application the voltage on Buck2 is preventing the PMIC to turn on.

    Sathish

  • 0 in reply to Sathish Vallamkonda
    Prodigy 70 points

    Hello Sathish,

    Thanks for the detailed explanation. We have resolved the issue and your speculation was accurate. 

    The root cause turned out to be Ethernet PHY. It back feeds 1.8V after 3V3 rises.

    Cheers,

    George