LM20136 Load Regulation

Ryuji

Guru 20090 points

Other Parts Discussed in Thread: LM20136

Hello,

I would like to know about the Load Regulation of LM20136.

(1) Condition of Electrical Characteristics of Load Regulation

There are the Figure and the Electrical Characteristics of Load regulation at the datasheet of LM20136.

For Figure (DS 6P.), there are the conditions of the L , R, Fsw and C.

But, for Electrical Characteristics there are not these conditions. Voltage and temperature condition only.

Please let me know the L, R, Fsw, C conditions of Electrical Characteristics of Load Regulation.

(2) Cause of the Load Regulation

Please let me know what parameters was affect Load Regulation.

Refference Voltage ? Gain of Amp ? line of feed back loop ?

Why voltage was changed when changing output current by that parameters?

Best Regards,
Ryuji Asaka

over 12 years ago

0 Vincenzo Pizzolante over 12 years ago

TI__Mastermind 24976 points

simply, the current is sensed interanlly...

the sense R increases with temperature and temperature increases with IOUT, so...

this "drift" has been characterized and shown in the device datasheet...

0 Vincenzo Pizzolante over 12 years ago in reply to Vincenzo Pizzolante

TI__Mastermind 24976 points

PS: if you see, the VOUT drift Vs IOUT follows (same shape) the FB voltage drift Vs temperature,

both the chart on page 6...

0 Daniel Tennant over 12 years ago

TI__Prodigy 320 points

Hi Ryuji,

1.) The load regulation in the EC table is probably based on the same circuit used to take the typical characteristic curves.

2.) The DC load regulation is dictated largely by the open loop gain of the control loop. The larger the open loop gain, the less the closed loop output resistance will be and therefore the better the load regulation (Zout ≈ Zopen_loop/(1+Open Loop gain). Load regulation can also be largely dictated by how VOUT is being sensed by the feedback loop. Incorrect sensing can cause the load regulation to either increase or decrease with load.

-Dan

0 Ryuji over 12 years ago in reply to Daniel Tennant

Guru 20090 points

Hello Vincenzo, Dan,

Thank you very much.

I understand that Load regulation is dicated some parameter's.

And Open loop gain is main cause of Load regulation.

Best Regards,

Ryuji Asaka

Power management

Power management forum

LM20136 Load Regulation