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TPS40170: Check the TPS40170 schematic

GARETH OU
Guru 11365 points
Part Number: TPS40170
Other Parts Discussed in Thread: LM5145, CSD18563Q5A

Hi 

Could you help check the TPS40170 schematic and any need to adjust?

1. Is the connection correct in Master and Slave mode?
2. Do you need to set both SS, RT and FB?
3. Is the input capacitance sufficient?

RS814-02-04.pdf

Thanks

  • 0
    TI__Guru 73072 points

    Hi Gareth,

     

    Here are some comments on the schematic:

     

    1. Consider using the LM5145 as it’s higher performance and lower cost than the TPS40170.

    2. Remove resistor in series with the VIN pin and tie directly to the drain of the high-side FET (as this is used for high-side FET voltage sensing).

    3. Consider using 60V or 80V FETs for better efficiency, e.g. CSD18563Q5A 60V NexFET. Also use asymmetrical FETs given the low duty cycle.

    4. R85 resistor can go gate to source (HDWV to SW), not to GND.

    5. Check compensation values using the quickstart calculator file using derated value for ceramic Cout at 12VDC.

    6. See app note snva803 for power stage layout best practices and optimal input cap location using 4 x 10nF/0603 and numerous 1210s.

     

    Regards,

    Tim

  • 0 in reply to Timothy Hegarty
    Guru 11365 points

     Hi Tim

    1. Now use Slave-180 ° mode , how to design RT ,SS , FB pin? Do you have a reference schematic ?

    2.I put this resister (R100 4.99K) in SLAVE page. This resister should need close to Master or Slave?

    Thanks

  • 0 in reply to GARETH OU
    TI__Guru 73072 points

    HI Gareth,

    The configuration of the M/S pin for MASTER or SLAVE is given in the datasheet. SYNC out of the master can be connected directly to SYNC in of the slave.

    One further comment on the schematic. The VIN for the power stage and controller must be derived from the same point, presumably the soft-started input rail, VR_VCC. This is because VIN - SW is sensed for high-side current sensing.

    Regards,

    Tim