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TPS65131: Voltage regulation issue

JIJU K
Prodigy 40 points
Part Number: TPS65131
Other Parts Discussed in Thread: TPS65135

Hi, I am using TPS65131 for the generation of +3.3V and -3.3V from input voltage 2.7V to 5.1V. I followed design example as shared in the datasheet. But the output voltage is not regulating properly. I am hereby attaching my design. I changed C201 to 30pF, C206 to 22pF and C210 to 4.7nF. Kindly suggest the modification, it is very urgent

  • 0
    TI__Mastermind 18550 points

    Hello,

    Please note that TPS65131 is specified for VPOS to be >= Vin+0.5V. So, for example, in the case of Vin=3.0V or higher, TPS65131 may not be able to regulate VPOS to 3.3V. With that said, at Vin=2.7V, what is not regulating in your design, VPOS or VNEG or both? Can you please provide bit more details of the behavior you are observing? what are the voltages you are getting on vpos/vneg rails?

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Prodigy 40 points

    Hi,

    My input voltages may vary from 2.7V to 5.1V. While I am applying 3.8V as input I am getting around +3.4V and -3.4V in VPOS and NEG respectively. But if I give Vin 4.1V VPOS will be 3.79V, but VNEG is keeping almost -3.4V. Since TPS65131 is voltage regulator it has to regulate the output in the designed value, isn't?. Please provide me a solution ASAP, its very urgent. If you want to contact me, you can call to +91-9020822667

    Regards

    JIJU

  • 0 in reply to JIJU K
    TI__Mastermind 18550 points

    Hello,

    TPS65131 has a boost converter for VPOS and a buck-boost converter for VNEG so you will not be able to get a regulated VPOS output voltage of 3.3V when your input supply is varying from 2.7V to 5.1V. Output VPOS can only be regulated when it is higher than Vin+0.5V as specified in the datasheet.

    Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Prodigy 40 points

    Hi,

    Thank you for your reply. Liaqat please suggest a part number similar to TPS65131 with buck boost regulation in both positive and negative outputs and current capacity 200mA in each outputs. Or alternatively please suggest a design modification to use TPS65151 with voltage regulation in both the outputs

    Regards

    JIJU

  • 0 in reply to JIJU K
    TI__Mastermind 18550 points

    Hello JIJU,

    I searched through TI power products and the closest device I see to your application need is TPS65135 which has SIMO buck-boost topology for both VPOS/VNEG and should be able to provide +/-3.3V output but unfortunately it will not be able to deliver 200mA load current. With your input supply range and +/-3.3V output, it should be able to achieve ~100mA. Unfortunately, there are no other split rail (+/-) converters in our portfolio with buck-boost topology for both VPOS/VNEG.

    Kind Regards,

    Liaqat