Using the LMZ21701SILT - Controlling Input Surge

Roger Dallas

Other Parts Discussed in Thread: LMZ21701, LMR14206

Hello,

I would like to use the LMZ21701SILT module in an application where 12V DC is the "typical" voltage (car battery supply and charge system) The nominal current from the module to the load would be 350-400mA, maximum current could peak occasionally to 750mA.

In this industrial system, surges can typically occur up to 20 or more volts due to the poor quality of the charging system. Fixing problems in that is not an option, so I am hoping to somehow protect the module from these surges. They are typically < 300 milliseconds.

Additionally, the input will be protected by a PTC.

With the maximum 17V DC input for the LMZ21701SILT, what's the best way to do this?

Thank you...

over 7 years ago

0 Denislav Petkov over 7 years ago

TI__Mastermind 18940 points

Hello Roger,

You will definitely need some kind of clamping circuit in front of the LMZ21701 to protect the input from going above the absolute maximum rating of the part.

Consider using a TVS or an active transient protection solution, like the ones used in automotive systems.

Is this a space constrained application?

You may also want to consider just using a device with higher input voltage rating than the LMZ21701 and eliminate the front-end protection circuitry all together. The module is a nice solution, but if you need to add additional circuitry it may defeat the purpose of using a module. The overall solution may be as large as just using a SIMPLE SWITCHER regulator IC instead of a module. There are many 36Vin (and higher) devices available from TI.

Here are a few examples:

http://www.ti.com/product/LMR23610

http://www.ti.com/product/LMR14206

http://www.ti.com/product/LM43601

Regards,

Denislav