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TPS65131: Help on building a split rail 15 volt power suply with 5v rail

gonçalo barroso
Prodigy 10 points
Part Number: TPS65131
Other Parts Discussed in Thread: TPS61030,

Hi,

Im designing a circuit for a project that im doign in my university witch is a thermometer with opamp signal conditioning connected to a arduino. Allthough its not asked of us im planning to take it a step forward and incorporate the thermometer in a portable data logger that is kinda usfull for a famaly member that need an equipmente like this. 

For this perpouse i need a power supply circuite that is able to supply 5v to power the atmega328P and +-15V to power the opamps (and the +15V for the wheatstone bridge).

As im still a begginer in this and i dont have the means to do a teste circuite in a breadboard im asking if anyone could take a look at the the circuite ive planned to power the above mencioned project.

To recape i have designed:

-5volt input usb/solar pannel so charge li ion 3.7v battery(using the tp4056 with protection ic to do this)

- +5V to power the atmega328p(using the TPS61030)

- +-15v to power the opamps(with min of 150mA)(using the TPS65131 with is input connected to the output of the TPS61030)

- main power source li ion battery 3,7V.

I Apolagize in advance for my spelling mistakes,

and thank you for helping.

  • +1
    TI__Mastermind 18550 points

    Hello,

    Your schematics is very hard to read even after magnifying. After reviewing TPS65131 section of the schematics, I have following feedback:

    -  C22 that is connected to CN pin should be 4.7nF and you schematics currently shows a very big 220uF capacitor at this pin.

    -  There is no output capacitor at the inverting converter output in your schematics. You should connect a 22uF capacitor at this output.

    -  For powering op-amp, I suggest to connect PSP and PSN pins to GND instead of VIN for a lower ripple operation.

    -  The MBRM120LT1G diode used in your schematics does not have enough margin for reverse break down voltage. Please use 30V MBRM130LT1G instead.

    After my reply, I will assign this thread to another engineer who is expert on TPS61030 to review that section of the schematics. You will get a response on that section of the schematics separately.

    Kind Regards,

    Liaqat

  • +1 in reply to Liaqat Khan
    TI__Guru* 78070 points

    Hello,

    I reviewed the portion of the TPS61030 schematic. It basically looks okay.  However, you should pay attention to the following:

    • Why leave the other two VOUT not connected?  Please use all VOUT pins to share the total load current.  
    • Remember to get your FB output voltage sensing from the output port of the circuit, which is the last output capacitor on your output rails.  
    • Follow our datasheet layout example when designing your PCB.  Especially remember to separate PGND and GND.  Refer to our EVM schematic in which PGND and GND are two different symbols to avoid confusion during routing, and use a net-tie to create the single point connection.

    Good luck,

    Youhao Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    Prodigy 10 points

    Thank you both for the fast a great feedback im going to correct my schematic acording to all the point mencioned.