TPS2394 different current ramps

Vitali Lach

Expert 1130 points

Other Parts Discussed in Thread: TPS2394

Hello,

I’ve got TPS2394 in my design whose behavior is different to evalboard.

They have also slightly different labels:

on Eval-Board: TPS2394 05KG4 D5LO

In Design: TPS2394 23K04 ALLR.

I’ve changed evalboard for design tests: Q1=AOB260L, C6 (flt timer)=4.7µF and C7 (ramp==1µF), Rsense=4mOhm. The load is 47000µF and 25 Ohm in parallel.

The problem is that the hot swap controller in the design has some turn on delay and a different current ramp that is more adverse for my MOSFET. I cant measure that behaviour on evalboard.

Do you have any idea what is wrong in the design? Was TPS2394 changed?

Best Regards.

Vitali

over 11 years ago

0 Vitali Lach over 11 years ago

Expert 1130 points

Hello,

this is the scope shot from evalboard. No delay there, max. current 5-6A for 200ms.

CH1: U out

CH2: UV-On signal

CH3: I out

0 Vitali Lach over 11 years ago in reply to Vitali Lach

Expert 1130 points

And this one is the scope shot from my design. There is a certain delay (700ms), current up to 7A, current ramp is different.

CH1: U out

CH2: UV-On signal

CH3: I out

0 Vitali Lach over 11 years ago in reply to Vitali Lach

Expert 1130 points

Hello,

would someone please answer the question up about?

I need urgently some solution for my project.

Best Regards.

0 Eric Wright over 11 years ago in reply to Vitali Lach

TI__Mastermind 42795 points

47000uF (0.047F?) is probably way too much output C for a controller of this sort (ie, this controller most likely cannot guarantee protection of the MOSFET with ultra-large output capacitance). You might look at the LM series of negative hotswaps with FET SOA protection.

0 Vitali Lach over 11 years ago in reply to Eric Wright

Expert 1130 points

Hello,

you are right, but LM series have long initialization delay and I need the one who acts like a switch. I also need 12V ability.

My question is related to difference between evalboard und my project: this ist what I cannot understand.

Best Regards

0 Vitali Lach over 11 years ago in reply to Vitali Lach

Expert 1130 points

Hello Eric,

I think that was something defective in PCB.

With another unite the current ramp is exactly the same like on the eval board.

Thank you for supporting me.

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TPS2394 different current ramps