• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 387 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.

TL720M05-Q1: hear noise when it works

Given Ding
Genius 10105 points
Part Number: TL720M05-Q1

Hi Team,

Here is a question from customer. 

when TL720M05-Q1 works in below sch, we can hear noise. Measured Vout waveform as below which seems has oscillation. I think the noise is caused by the ripple

. 

I have asked customer to change to a Electrolytic Cap, and then there is no noise and Vout ripple is also small. And datasheet indicate it's a PNP type LDO, then I think there should be min ESR requirement but datasheet has no such spec

1. could you please kindly help on check if there is min ESR requirement and Cout max requirement?  In below sch, total Cout is ~50uf. 

2. customer can accept the large ripple when using ceramic caps and can accept the noise, do you think it's OK? Or since it may be a stability issue, then you still recommend to change BOM. 

Thanks. 

BRs

Given

  • 0
    TI__Guru 55940 points

    Hi Given,

    TL720M05-Q1 was designed, tested, and characterized for use with ceramic output capacitors.  Generally ceramic stable regulators do not state a minimum ESR as the trace resistance between the LDO and the capacitor is enough to satisfy any requirement.  This datasheet does provide additional detail on ESR vs capacitance and load in Figures 11 and 12:

    We would not generally recommend an output voltage that is oscillating; however, this is ultimately your customer's choice as it is their application.

    We do highly recommend prototyping the application and performing load transient tests as described in the following Application Report to get a sense for the stability of your desired capacitor(s) in your application:

    http://www.ti.com/lit/an/slva381b/slva381b.pdf

    Very Respectfully,

    Ryan