• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 63 subscribers
  • Views 912 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS63001 output variation

Matthew Chapman
Prodigy 40 points
Other Parts Discussed in Thread: TPS63001

  • The TPS63001's sole purpose on my board is to supply 3.3v, <1A typ. to a cell phone module.
  • I am seeing an output variation as low as 3.27v at no-load to light load at ambient temperature and a further decrease beyond 300mA out.
  • Output voltage continued to decrease as temperature dropped.  At -30C my output was as low as 3.1v.
  • For consistent testing load was simulated to provide peak and average current required by the modem.  
  • Input voltage:  4-cell, 3.6v Lithium ion battery.  Our custom battery pack does not fall below 3.3v at -40C.    
  • The enable pin is controlled via the micro from a separate 3.3v rail.    
  • PGND and GND were tied at the GND pin via a zero ohm resistor.  The resistor was placed encase a ferrite bead would have been necessary to filter noise from the PGND plane.
  • Inductor is 4.7uH Murata chip recommended on the TPS63001 data sheet.
  • Pads on the bottom plane are not tied connected.
  • Thermals were turned off.  
  • Could you evaluate my design giving pointers at where I might start to rectify my discrepancy?  

  • 0
    TI__Expert 7110 points
    Do you see the voltage shift DC wise when measuring the voltage wit a multimeter? Or are this the values you see when measuring with the oscilloscope?
    What definitely can cause an unexpected output behavior is the additional resistor between GND and PGND. Even if you have a labeled 0Ohm assembled, you will add a resistance to the loop.
    I'd recommend to connect the GND's with a direct star-point right at the device as done at the evaluation module:
    www.ti.com/.../TPS63000EVM-148
  • 0 in reply to Florian Feckl
    Prodigy 40 points
    Thank you for your input. I was seeing the same voltage on each calibrated device, multi-meter and oscillioscope. I pulled the shunt resistor and measured 0.2 miliohm. I then shorted the two pads with the same result. Even if it wasn't a fix, I expected to see a variation in behavior for better or worse.
    After shorting the pads I used the o-scope to verify there was no difference across on each pad.