Customer of mine intend to use LMR14050-Q1 (LMR14050SSQDDARQ1) in their car audio system however they’re seeing voltage overshoot and undershoot at rising and falling edge causing some interference with the radio frequencies
I’ve attached the material for your reference.
My questions are as below:
- the Rt value in customer schematic is 84K, thus calculated switching frequency is 308KHz. Would this cause the AM interference?
- Also, the value output capacitor is rather huge (3400uF). Would this cause the voltage overshoot/undershoot?
- Is there any way to reduce the ringing voltage effectively?
- could you help to review and comment the schematic and layout?
LMR14050-Q1 Interference issue.pdf
I review the circuit and layout:
1. Input bypassing design is bad, C601 is too small and voltage rating is not enough, pls change C601 to 0.22uF/50V parallel with 4.7uF/50V
2. the snubber circuit R609 is 2.2ohm? C610 is 5600pF? pls try R609 4.7ohm and C610 1000pF/50V first.
3. you may also add 4.7ohm in series with C602 to limit switching rising edge lsew rate.
4. Better to change the layout to improve input bypasing and heat shrink.
In reply to Andy Chen:
LV/MV CCP DC/DC Applications
In reply to Eng Lih Khaw:
Pardon me for delay.
Could you send it to email@example.com ?
Thank you for your support!
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.