LM5145-Q1: Output Current sinking

Dave Chowning

Prodigy 110 points

Part Number: LM5145-Q1
Other Parts Discussed in Thread: LM5145, TPS40170

Can the output sinking FET of the LM5145 sink 8 amps of current from the load?

over 2 years ago

0 Timothy Hegarty over 2 years ago

TI__Guru 59187 points

Hi Dave,

"Output sinking FET" is non-standard terminology, I assume you mean the low-side FET. The LM5145 is a buck controller with current sourced to the load. Current sinking only happens transiently if Vout overshoots its setpoint (e.g. during a load-off transient). in this case, the low-side FEt is left on to ramp the inductor current negative and discharge the output cap as needed.

Regards,

Tim

0 Dave Chowning over 2 years ago in reply to Timothy Hegarty

Prodigy 110 points

The voltage from the load will be higher than the buck controller output so it needs to sink current for a specified time interval. The buck controller will also source current for a specified time interval.

This worked for the TPS40170 which I used in the past. I want to switch over to the LM5145 for the same app.

0 Timothy Hegarty over 2 years ago in reply to Dave Chowning

TI__Guru 59187 points

Ok, if it worked for the TPS40170, then the LM5145 should be fine (the loop architecture is effectively the same in both parts). The controller itself doesn't sink any current, it's the power stage. The loop will respond to bring VOUT down to its programmed setpoint.

Regards,

Tim

0 Dave Chowning over 2 years ago in reply to Timothy Hegarty

Prodigy 110 points

Thanks Tim I'll try it out to be sure

0 Timothy Hegarty over 2 years ago in reply to Dave Chowning

TI__Guru 59187 points

Thanks, Dave.

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LM5145-Q1: Output Current sinking