LM5176-Q1: LM5176QPWPTQ1

Hi Parvin,

Thank you for reaching out, I cannot access the files you have shared here, is there another way you can share them?

Regarding as to why there is so much consumption might be due to losses and layout, normally at no load the consumption should be in mWatts.

Thank you

BR,

Haroon

Hi Haroon, could you please share your email address, so that I will share the files?

thank you

Hi Parvin,

you can use the private mail feature from this forum - hover over my name and select send private message.

Please drop a note here that you have sent a private message so that I know to check the inbox - otherwise it might get lost.

Best regards,

 Stefan

Note: please also provide the Excel quickstart calculator - can be found on the product page:

https://www.ti.com/tool/download/SNVC208

Best regards,

 Stefan

Hi Stefan, 

Please check your inbox for the message.

thanks

Parvin 

Hi  Parvin,

thanks for the note here.

To attach files in the mail (same link here in the forum) just use drag and drop.

Best regards,

 Stefan

Hi Stefan, I have attached the files here as well as in your private messages. 

When I was designing this section, I had it reviewed by TI.

Please also refer to the TI tickets related to this design.  CS0947115 and CS1361714

thanks

PArvin6507.LM5176.zip

Hi Parvin,

thank you for sharing the file.

As you can see from the Quickstart calculator the main losses are in the inductor. This are the core losses due to the changing magnetization of the inductor.

This can be improved by reducing the switching frequency and/or increasing the inductor.

E.g. with 300kHz switching frequency and a 3uH inductor the estimated inductor loss go down to 1.4W with no load.

If no load efficiency is very important you can also check out the LM5175 with DCM mode enabled. 

Both devices are pin compatible but you need to adjust the the RT resistor.

Note:

BIAS should be connected to GND or VIN if not used.

Best regards,

 Stefan

HI Parvin,

when referring to another thread please add a link to that thread.

(CS0947115 and CS1361714 seem not be be valid ticket numbers)

Thanks,

 Stefan

Hi Stefan, Thanks for your response.

I will try the reduced frequency and increase in the inductor value.

I have used 100nF capacitor at BIAS pin, should I ground this pin directly?

Actually, it is not No load (sorry my bad), it is with very minimal load .

These are the links of the reference cases

https://support.ti.com/csm?id=ticket&table=sn_customerservice_case&sys_id=e1f2c9f647b6d5d05c930541e36d431b&view=sp

https://support.ti.com/csm?id=ticket&table=sn_customerservice_case&sys_id=838143a7471e0950d4f52e61e36d43a2&view=sp

thanks

Parvin 

Hi Parvin,

yes, you can connect BIAS directly to GND.

OK, I see - this are tickets from the  Customer Service and not E2E threads.

I do not have access to them.

Best regards,

 Stefan

Hi Stefan,

As I have mentioned earlier, we have two different designs using the same IC.

1. MDR7- VIN=9V to 36V, Vout= 13.5V, Iout = 15A

2. CDR7- VIN=9V to 36V, Vout= 12V, Iout = 11A

I have attached here two different folders fro these designs.

I have tried changing the switching frequency and increasing the inductor on the CDR7 design.

1. changing the frequency from 340KHz to 300 Khz,  with any inductor did not help to reduce the power consumption.

2. I tried changing the inductor from 1.5uH to 2.2uH, 4.7uH and 10uH. This helmed me a lot to reduce the power consumption.

RT=23.4K , L=1.5uH  - 5.52Watts

RT=27K , L=1.5uH  - 6Watts

RT=23.4K, L=2.2uH,2.7mohm - 2.88 Watts

RT=23.4K, L=4.7uH, 15mohm- 2.16 Watts

RT=23.4K, L=10uH, 43mohm - 1.92 Watts

RT=23.4K, L=10uH, 16.1mohm -1.92 Watts

Based on these trials, I plan to keep the switching frequency as is and change the inductor on bot

I have attached the spreadsheets with simulation results with different inductors.

Please confirm that the inductor values chosen are ok in terms of DC resistance, current etc. Also please let me know if  I am not braking something else in the design.

For CDR7, IL max is 16.3A, Is it ok to use SRP1270-4R7M- 4.7uH  15A 11.2 mOhms or SRP1270-3R3M- 3.3uH Shld 18A 6.6mOhm

For MDR7 IL max is 24.44, Is it ok to use XAL1010-562MED - 5.6uH Shld 20% 21.2A 6.93mOhms or XAL1010-472MED- 4.7uH Shld 20% 24A 5.7mOhms 

thanks

PArvin 

MDR7.zipCDR7.ziph designs.

Hi Parvin,

It looks OK from my side  - just two comments to check:

keep the slope capacitor to close to the suggested or next lower value.

check if the loss in a MSOFET of ~2.3W is OK for your application. This would result in a temp increase of 115  Degree against Ambient Temperature.
(Loss in MOSFET at max Current)

Best regards,

 Stefan