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TPSM8D6C24: No voltage output

Part Number: TPSM8D6C24

Hi,

We use TPSM8D6C24 as PMIC on our EVB, but it can't output any power (Vout = 0)

VoutA/VoutB should be 0.75/0.55 by pin strapping.

TPSM8D6C24.pdf

How to debug the case?

Below is the debug flow:

1. We replace R283/R290/R284/R291 from DNP to 0R.

2. PVIN = 3.3V, AVIN = 5V (3.3V -> LTC3205B-5 -> 5V)

3. EN_A/EN_B = 3.3V

4. VDD5_A/VDD5_B = 5V

5. BP1V5_A/BP1V5_B = 1.5V

6. PMBus connection is normal.

7. Vout_A/Vout_B = 0

  • Because of the Thanksgiving holiday in the U.S., TI E2E design support forum responses may be delayed the week of Nov. 21. Thank you for your patience.

  •  

    My apologies for the delay in getting back to you on this issue, and that you are having problems with the TPSM8D6C24 module.

    I believe the source of your problem is R307, a 0-ohm resistor connecting VSHARE_A to VSHARE_B.

    VSHARE_X is the low-impedance output of the voltage error amplifier used to drive the current regulation loop of follower devices in a stacked configuration, it should not be connected to the VSHARE of an independent output voltage, like you have here as that will force the two rails to fight with each other.

    While not the problem here, BCX_CLK and BCX_DAT are not used when the part of an independent single phase "stand alone" conversion and R308 and R309 can also be removed.

    Some further recommendations for improvements of this schematic design when you can make changes:

    1) I do not recommend placing ferrite beads between the Pin programming resistors and the ground of the TPSM8D6C24 as this could add to the sensed resistance of the pin-strap resistors when pin detection is run and the margins on detection can be fairly small.

    2) When powering AVIN and VDD5 from an external 5V source, I would recommend connecting the external 5V directly to VDD5 and using the 10Ω resistor to filter noise from the external 5V source and VDD5's MOSFET switching from AVIN.  That will increase the available VDD5 voltage and reduce the switching noise on AVIN.

    3) Both rails ADRSEL programming are selecting Auto-detect for SYNC.  This can lead to contention for SYNC if both rails are enabled at the same time, with both devices detecting no SYNC on the input and both trying to drive the SYNC pin.  It is preferred for one of them to be programmed for SYNC_IN and the other SYNC_IN, SYNC_OUT, or Auto Detect - unless the two rails will be programmed for different switching frequencies.  If the switching frequencies are different, both MUST be programmed for SYNC_IN.