LMR38010: Power Consumption of LMR38010FDDAR

Hello, 

That power consumption sounds too high. 

Do you have a schematic you can share? 

Regards,

Harrison Overturf 

Hi Harrison,

I've inserted an image of the schematic.  

Best

Hello,

Thanks for sharing the schematic, I don't see any red flags. 

Are you using an FPWM enabled part? 

Are there other devices on the board that may be consuming current?

Regards,

Harrison Overturf 

Hi Harrison,

This is device does have FPWM (does it switch automatically between that and PFM, or does this specific part number only support FPWM?).  

For a test board, there are only three other components--they are used for input protection: resistor, diode, TVS diode.  Resistor is only consuming about 4.5 mW when 50 V is supplied.  Just going by heat produced, the 38010 is the component that generates significant heat, reaching 50 C on the package surface at room temperature (with load and without load).  

Best

Hello,

Have you tested this on multiple devices or is it just one device? If you have just seen it on one device can you try swapping that device for another. 

Have you tested this device on the EVM and seen this occur? 

Regards,

Harrison Overturf 

Hi Harrison,

I did use the LMR38020EVM board (but swapped out the 8020 for the 8010 and removed/added passives to match the above schematic, and it shows similar behavior.  The buck only heats to about 30 C on the eval board due to the much better heat sinking from what I can tell.  The numbers I have with the modified EVM board are 0.568 W no load @ 50 V input.  1.43 W with a 30 ohm load @ 50 V input.  Switching frequency set to about 1.3 MHz, 3.3 V output voltage.  

I've tested two of our own boards total so far--one with just the power circuitry and one with additional electronics.  Same behavior.  

I just purchased a second EVM which I wanted to test unchanged to get a baseline.  Should get it by Monday.  

Best

Hello,

Is the 0.568W in reference to the amount of power dissipated by the IC? For 50Vin, no load that would be around 11mA input current, is this what you're measuring? 

Regards,

Harrison Overturf 

Hi Harrison,

That is correct, I measure between 11-13 mA on our pcb (just the buck converter and power protection components populated). 

I just plugged in a new LMR38020EVM to a 50 V input.  No load is attached at the output and 5 V is measured.  The current @50 V is about 9.8 mA.  Is this expected?  

Best

Hello,

I generated a Webench design based on this situation and it appears that this input current is to be expected (I checked for the case of 50Vin, 3.3Vout / 5Vout, 110mA load, FPWM, 1MHz).

Here is the link to the design for your review: Power Designer (ti.com) 

Regards,

Harrison Overturf 

Hi Harrison,

I'm unable to see the design.  I get: 

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What is expected for a no load condition?  I measure about 9.8 mA without a load attached.  

Best

Hi Denislav,

Thanks for the reply.  Where does the 1 mA come from?  Is it consumed as part of the feedback?  

PFM mode would mean a different version of the chip?

Best

Hi Denislav,

Thanks.  

The 9.8 mA @50 V was measured on an EVM board for the 8020, nothing attached to the output (Vout).  What would be responsible for that current draw?  I may be missing where that 1mA you mentioned is coming from.  

Best

Hi Denislav,

Sounds good, thanks!

Best