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TPS54541: URGENT ! Wrong Regulation under Load, Good Regulation under No Load

Ignacio Diz
Prodigy 75 points
Part Number: TPS54541
Other Parts Discussed in Thread: LM5085

Hi

Our 5 channel battery charger for marine radio beacons consists in 5 constant current channels at 0.4A each

Also temperature is quite high (would be fine to go with external mosfet solution?)

Under no load  TPS54541 haves very low output ripple

Wen one of more channels are under load, output ripple is very high (1V PEAK to PEAK) and it is impacting our DVDT charging algorithm

Full Schematic in attached

Please help me to solve the issue to avoid part change




Please EESL Charger V15.pdf

  • 0
    Prodigy 75 points

    Can this changes solve the issue 

    R146, C70, R147, C71 and L7 Adjustments

    3073.WBDesign70 Patch 1.pdf

  • 0 in reply to Ignacio Diz
    TI__Expert 3766 points

    Hi Ignacio,

    Can you fill out this excel spreadsheet with your design parameters? In the meantime I will continue to look at your schematic and scope shots.

    Regards,

    Henry7750.LM(2)5085_Quick_Start.xls

  • 0 in reply to Henry Kou
    Prodigy 75 points

    Hi @Henry Kou

    For sample B we shoud patch TPS54541 for customer demostration (Please find changes in attached)

    Our algorithm is DVDT based and very sensitive to DCDC Buck output changes, if a radio beacon is inserted, it can impact DVDV of a channel in charging process

    Waiting for your reply

    NACHO_LM5085.pdf

  • +1 in reply to Ignacio Diz
    TI__Expert 3766 points

    Hi Ignacio,

    I accidentally gave you the wrong excel calculator, but looking at your schematic I was able to fill out this new excel calculator with recommended values.

    The main changes I would make to your schematic are shown below. Currently I have it setup with 2.5A IOUT per TPS54541 device from your information, just wanted to confirm that with you.

    Let me know if you have further issues.quickstart_mods.xls

    Regards,

    Henry

  • 0 in reply to Henry Kou
    Prodigy 75 points

    Hi Henry


    Your mistake is not a bad a idea at all because external MOSFET solution (LM5085) will improve thermal behaviour

    TPS54541 integrated controller thermal behaviour is not to good solution is 

     Regarding the output riple of (0.095) would be fine to red6uce it d6ownto 0.5

    Furthermore when a battery is inserted it can cause change at DCDC output and, then impact D6VD6T algorithm of any battery being under charge

  • 0 in reply to Ignacio Diz
    TI__Expert 3766 points

    Hi Ignacio,

    To reduce your output ripple, you will need more COUT, which could affect your control loop. You can perform an AC simulation or transient analysis sim to make sure. In addition, I am not familiar with the D6VD6T algorithm. Are you talking about line transient changes or input voltage changes to the device?

    Regards,

    Henry

  • 0 in reply to Henry Kou
    Prodigy 75 points

    DC Input is fine and stable :)

    I mean transient regulation when  battery is insertion or removal whuile other channels are charging

    Our DVDT algorithm looks stop of voltaje ascending tendence