LMZ31704EVM-003: no power supply ouput

Randy Perrin

Part Number: LMZ31704EVM-003

I have a deisgn with the LMZ31704RVQT First time I have erver used this component and not having any sucesses

When connected to a 10V supply that is only outputing about 1.27V. I attempted to folow the deisgn guildlines per the simulation but must of done something worng. Can you look at the SCH and see for any errors ? I have verified PVIN and GND GNd conections

over 2 years ago

0 Nancy Zhang over 2 years ago

TI__Mastermind 45980 points

Hi Randy,

The schematic is blurry and I could not see it. Could you send me the pdf file to my email? I will review it and get you back soon.

nancy_zhang@ti.com

Thanks,

Nancy

0 Lucia Gao over 2 years ago

TI__Genius 13110 points

Hi ,

Sorry that I will close this threat first. Please re-open it if there is any future question.

BRs,

Lucia

0 Nancy Zhang over 2 years ago

TI__Mastermind 45980 points

Hi Randy,

We didn't click" TI thinks resolved" button and just closed it since I required schematic to do offline debug and didn't get your feedback about a month. Review your schematic again and found Pin28 of soft start pin should not be connected to GND. If you don't want to add external cap and you should leave it open and not connect it to GND. Is it possible to lift this pin open and power up again?

Hope this helps.

Thanks,

Nancy

0 Randy Perrin over 2 years ago in reply to Nancy Zhang

Prodigy 55 points

Hi Nacy, I have another issue. I hace a 7.8V input and 5.2V output I start current limititing at 1A load. The output is a appoximentaly a 2,2 ms pulse A16ms per pulse Sucgestions?.

0 Nancy Zhang over 2 years ago in reply to Randy Perrin

TI__Mastermind 45980 points

Hi Randy,

Is this same project with above you post here? Did you fix the 1.27Voutput issue? If this is same schematic, it should not enter the current limit at 1A output current. Here are my suggestions.

1. Check the input power supple to see if there is any current limit from input source.

2. Check if input cap 2x22uF are close to input pins, if not, try to add a 47uF ceramic cap close to PVIN pins

3. Check if output cap 1x47uF is close to VOUT pins, if not, try to add a 47uF ceramic cap close to Vout pins

4. If above suggestions are not working, Could you send me the sch and layout file? My email address: nancy_zhang@ti.com.

Thanks,

Nancy

0 Randy Perrin over 2 years ago in reply to Nancy Zhang

Prodigy 55 points

Nacy This is the same project and cutting STLEL and SSTR fixed the startup issue. Thanks there is now power source current limiting. The 2X 22 caps are close to the PVIN pins with multiple planes on other latyers. I also added 1 100uF AE cap to the put. I can try to add more ceramic caps. I can send the SCH and layout do you have altium. If so I will share the project. I also have scope shots of the output when it goes into currentt limiting.