• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 578 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.

High ripple output on LMZ14203HTZ

Nick Anderson
Prodigy 10 points

Have a small custom carrier board designed to a host a NVIDIA TX1. 5v power supply being fed 10-30v DC IN is showing a 14Khz sawtooth output ripple to the tune of ~200mV or more as measured on the scope, sometimes more. This high ripple is then corrupting down stream high speed signals (USB specifically) but having trouble figuring out why the chip is oscillating. Schematic is below and very similar to the reference design. 

C6/C7 are C3225X5R1E226M250AC. Mfg doesn't seem to publish an ESR but it says "low". C3/C4 are C3216X7R1H475K160AC. 

Any ideas? 

  • 0
    TI__Genius 15810 points
    Is this circuit loaded when you see a 14kHz wave? These devices work on a constant on time principle and do not have an internal error amplifier. Instead they have a comparator and having some hysteresis is good. Adding a Cff capacitor in parallel with the upper feedback resistor couples a slight bit of hysteresis on to the FB node which should help.