LMR36015: Asking for the LMR36015 peak an abnormal issue

SHH

Part Number: LMR36015

Hi Team,

Customer is using LMR36015 as 5V system power.

Please kindly help for cusotmer's four question here.
1. the system load varies widely as WIFI and image sensor function, load current(max load condition) measured result as below:
system overall load is not high, but peak current is high;

2. In datasheet, it shows that LMR36015's limit current is 1.5A. This limit current is peak current or continues current?

3. customer found the design will lose 5V output sometimes. Does this have anything to do with system load(max load condition)?

4. Do you have any comments that the design can improve the current varies at LM36015 side?

BR,
SHH

over 6 years ago

0 Katelyn Wiggenhorn over 6 years ago

TI__Genius 11040 points

Hello,

The maximum current of 1.5A is continuous.

Loosing regulation will happen in an overload condition. The current limits can be found in the datasheet. If the minimum inductor current goes above the low side current limit, the output voltage will droop. The maximum inductor current will also be limited by the high side current limit.

Could you share the schematic for review?

Thanks,
Katelyn

0 SHH over 6 years ago in reply to Katelyn Wiggenhorn

TI__Mastermind 32206 points

Hi Katelyn,
thanks for reply.

Would you tell us the peak current limit of LMR36015?
customer's system have high peak current, average current is not high.
they are trying to lower the peak current, do you have any comments?

customer only can share DC/DC related as attached.
txn.box.com/.../188zzuv7kivxkxejksn0zixdk6nzcp4e

BR,
SHH

0 Katelyn Wiggenhorn over 6 years ago in reply to SHH

TI__Genius 11040 points

Hello,

You can find the peak current command in the datasheet EC table as (ISC). The minimum is 2A and the maximum is 2.8A. Do you have a waveform of the inductor current during this condition?

Also, thank you for sharing the schematic. There is not anything that I would expect to cause this problem in the schematic.

Best Regards,
Katelyn

0 Katelyn Wiggenhorn over 6 years ago in reply to Katelyn Wiggenhorn

TI__Genius 11040 points

Hello,

Could you share a waveform of the output voltage and the inductor current when the output voltage drops? This will help us understand the conditions which cause the output voltage to drop.

Thank you,
Katelyn

0 SHH over 6 years ago in reply to Katelyn Wiggenhorn

TI__Mastermind 32206 points

Hi Katelyn,

the following picture is the current after L(peak 2.04A is max value).

please share your comment on this waveform.

BR,

SHH

0 Katelyn Wiggenhorn over 6 years ago in reply to SHH

TI__Genius 11040 points

Hello,

Would you be able to share a zoomed in view to about 2-5us per division when the output voltage drops? From this image it is possible that the device is entering current limit.

Thank you,

Katelyn

0 Katelyn Wiggenhorn over 6 years ago in reply to Katelyn Wiggenhorn

TI__Genius 11040 points

Hello,

I want to follow up with you. Have you had a chance to take a zoomed in waveform?

Thank you,

Katelyn

0 Katelyn Wiggenhorn over 6 years ago in reply to Katelyn Wiggenhorn

TI__Genius 11040 points

Hello,

Due to inactivity, I am going to close this thread. If you have any remaining questions, please feel free to respond to this post and the thread will reopen.

Thank you,

Katelyn

0 SHH over 6 years ago in reply to Katelyn Wiggenhorn

TI__Mastermind 32206 points

Hi Katelyn,

Customer found Voltage drop due to Vin dropped<5V, no related to DC/DC.
But customer still trying to lower peak current, do you have comments on this(faster response to load change)?
As the peak current affected VIN input,the source of VIN was from AC transformer,
When peak current is high, it will cause a high drop voltage on VIN.

BR,

SHH

0 Katelyn Wiggenhorn over 6 years ago in reply to SHH

TI__Genius 11040 points

Hello,

Is this waveform above of the load current? Would you also be able to reshare the schematic? I want to review again to see if there is anything that can be done to improve transient performance.

Thank you,

Katelyn

0 Katelyn Wiggenhorn over 6 years ago in reply to Katelyn Wiggenhorn

TI__Genius 11040 points

Hello,

Due to inactivity, I am going to close this thread. Please respond to reopen this thread, or feel free to send me an e-mail.

Best Regards,

Katelyn

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LMR36015: Asking for the LMR36015 peak an abnormal issue