LM5069: LM5069 replace LT4363

Yang Wu

Part Number: LM5069
Other Parts Discussed in Thread: LM74800-Q1, TPS2663

Hi Team,

My customer is considering using LT4363 for surge protection. I find that LM5069 is very similar to LT4363. However, LM5069 supports minimum 9V and LT4363 supports 4V. The input voltage range of cusstomer's project is 8V ~ 30V.

Do we have device supports lower input voltage for surge protection? Or do you have other solution?

thanks a lot.

Best regards,

Yang

over 5 years ago

0 Rakesh over 5 years ago

TI__Guru** 105361 points

Hi Yang,

What is the max load current. ? For systems, up to 6A load current TPS2663 can be used. For higher current systems, LM74800-Q1 can be used for protecting the load from surges.

Best Regards, Rakesh

0 Yang Wu over 5 years ago in reply to Rakesh

TI__Expert 3320 points

Hi Rakesh,

Thanks for your reply, Let's communicate offline then I can provide the SCH.

Best regards,

Yang

0 Yang Wu over 5 years ago in reply to Yang Wu

TI__Expert 3320 points

Hi Rakesh,

The max current is lower than 2A, so I have promoted TPS26600 to customer.

Based on EVM test, customer found that for startup, it has no surge current and Vout ramps up gradually. While if there has input transient from 10V to 30V, there has huge inrush current as shown below in pink. Yellow is input voltage.

Do you know why it happens and how to solve it?

thanks.

PS, what's your email address? we may communicate offline.

Best regards,

Yang

0 Rakesh over 5 years ago in reply to Yang Wu

TI__Guru** 105361 points

Hi Yang,

What is the output capacitor during this test ?

The device is already ON with Vin=10V. so, when you apply input step from 10V to 30V in 2ms, the output capacitor draws current I=Cout*20V/2ms. Can you verify that?

Best Regards, Rakesh

0 Yang Wu over 5 years ago in reply to Rakesh

TI__Expert 3320 points

Hi Rakesh,

The test is based on EVM:https://www.ti.com/tool/TPS26600-02EVM

Customer modified C6 to 100nF.

In addition, this post is actally the same as this one I asked you before:https://e2e.ti.com/support/power-management/f/196/p/910467/3365546#3365546

About the value of internal pull-up resistor on \SHDN pin, you said it's 1Mohm. I suppose it's typical value, what's min and max values?

Customer's requirement is very simply, limit the surge current below 100mA during 10V to 30V transient.

thanks a lot.

Best regards,

Yang

0 Rakesh over 5 years ago in reply to Yang Wu

TI__Guru** 105361 points

Hi Yang,

Can you also check and inform us the value of output capacitance Cout

Best Regards, Rakesh

0 Yang Wu over 5 years ago in reply to Rakesh

TI__Expert 3320 points

Hi Rakesh,

As you can see above SCH, Cout is C5 as 47uF.

thanks.

Best regards,

Yang

0 Rakesh over 5 years ago in reply to Yang Wu

TI__Guru** 105361 points

Hi Yang,

Something looks strange. With 47uF, the inrush current would be = 47uF * 20V/2ms = 470mA for 20V step input in 2ms rise time.

Can you share Vin, Vout, input current and dvdt pin voltage during 10V to 30V transient. The device is already ON with 10V input. You will need to increase the UVLO threshold to make the soft-start to function.

Best Regards, Rakesh

0 Yang Wu over 5 years ago in reply to Rakesh

TI__Expert 3320 points

Hi Rakesh,

I understand. if customer wants to limit inrush current, one solution is that they can retoggle Enable? right?

I post another question in our previous post, could you also help reply?

https://e2e.ti.com/support/power-management/f/196/p/3366157/reply?ReplyToContentTypeID=1

thanks a lot.

Best regards,

Yang

0 Rakesh over 5 years ago in reply to Yang Wu

TI__Guru** 105361 points

Correct Yang.

Best Regards, Rakesh

Power management

Power management forum

LM5069: LM5069 replace LT4363