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LMR14010A: Looking for ultra low regulator

Amir Eshraghi
Expert 1230 points
Part Number: LMR14010A
Other Parts Discussed in Thread: TPS40305, TLE2426

Hi

I am looking for regulator to conevert 10 -30V to 5V which goes to voltage reference. I need a regulator that have the least ripple and voltage swing when input voltage changes. 

I am already using TPS40305DRCR to convert 12v from LM34936RHFR to 5v but the issue is every time large load turns on 12v  regulator all voltages drops which effect my amplifiers.

There is 24 external power supply which connect to LM34936RHFR  and then goes to TPS40305DRCR.  Please let me know if you  have any questions.

A-1300 X09-pages-3.pdf

Thank you.

  • 0
    TI__Guru 58225 points

    Hello Amir,

    Dependent on the load on the 12V line, you can possibly stabilize this one more with additional capacitors. Another possibility would be an additional LDO between the TPS40305 and your 5V reference.

    In general using a step down converter to regulate transients on the 12V line should be good as step down converters can have a relatively high crossover frequency. So the question is if an additional LDO would be an option or if you want to optimize the buck converter to fulfill your requirements on the 5V line, but then you need to define your requirements.

  • 0 in reply to Brigitte
    Expert 1230 points

    Hi

    Thanks for quick replay. The max load on my 12V is 2.5A which cause drop of 0.120mV  which cascade on my 5V switching regulator and 3.3VLDO regulator (All drop)  My main issue is this voltage swing cause major spike on my amplifier circuit because my VGND TLE2426 to change and cause my transimpedance amplifier out put change too.

    I am looking for something to keep the VGND from changing when load turns on, I even tried voltage reference.

    Thank you

  • 0 in reply to Amir Eshraghi
    TI__Guru 58225 points

    Hello Amir,

    So even with a linear regulator from 12V down to 5V, you have observed a voltage change on the 5V line of 120mV? Are you using a solid GND plane?

    Normally the load should not cause such a voltage change on the other end of your system. This might point to a layout issue.

  • 0 in reply to Brigitte
    Expert 1230 points

    Hi

    Thanks for reply, I have attached the power supply layout, but the pcb is four layer with one layer dedicated to  ground. I also follow to EVM board layout for both regulators.

    Please let me know if you have any questions.

    Below is the 5V regulator

    and below is 12V buck boost regulator

  • 0 in reply to Amir Eshraghi
    TI__Guru 58225 points

    Hello Amir,

    Please repost the pictures as they did not come through.

    Please check if additional output capacitors on the 5V rail change the transient response when the load on the 12V line starts. Please measure the difference.