UA723: Foldback circuit resistors value

Bala Thirumavalavan

Prodigy 110 points

Part Number: UA723

Hi Stephen,

Could you tell me how to calculate R3 and R4 for foldback current limiting circuit (figure 6)?

Thanks,

over 4 years ago

0 JCHK over 4 years ago

TI__Mastermind 44790 points

Hi Bala,

Stephen is out of office for the next two weeks. R3 and R4 will be a function of your output. Please see the table below for suggested values:

Does this answer your question?

0 Bala Thirumavalavan over 4 years ago in reply to JCHK

Prodigy 110 points

Hi John,

I am trying to figure out the Foldback current limiting function, not the Vout. According to Table 2, R3 and R4 on figure 6 are function of Foldback current limiting. I don't see any reference to current limiting on table 1.

Thanks,

0 JCHK over 4 years ago in reply to Bala Thirumavalavan

TI__Mastermind 44790 points

Hi Bala,

The current limit (IKNEE) is set by this:

Does this help to clarify?

0 Bala Thirumavalavan over 4 years ago in reply to JCHK

Prodigy 110 points

No, current limit knee is set by: (VoR3+(R3+R4) *65)/Rsc * R4 for figure 6

0 Jason Song over 4 years ago in reply to Bala Thirumavalavan

TI__Mastermind 23361 points

Hey Bala,

Have you solved the problem yet? In table 2, there is an equation for the current limit calculation. As long as the values of R3 and R5 give you the limit you need, there is no special requirement on the values of the two resistors.

Regards,
Jason Song

Power management

Power management forum

UA723: Foldback circuit resistors value