LM5117: CC/CV Configuration at high voltage

Keshav Raj

Part Number: LM5117
Other Parts Discussed in Thread: LMV431

Hello,

I am trying to use the LM5117 in CC/CV mode to charge a 10 cell lithium ion battery pack. In order to do this, I intend to configure the LM5117 for a constant current of 2A with an output voltage of 42V once the battery enters saturation charge.

I used application note SNVA829 to help with this, however have gotten stuck in selecting a precision voltage reference as the LMV431 only goes up to 30V. I short search for alternatives didn't yield any results supporting a high enough voltage.

My current thoughts are to perhaps use a zener(s) (e.g. 20V zener voltage) in series with the LMV431 to reduce the reference voltage requirement.

Would this work? But also am I going in the right direction by using the LM5117 for this purpose in the first place?

Cheers,

over 3 years ago

+1 David Baba over 3 years ago

TI__Mastermind 28660 points

Hello Raj,

The idea of adding a Zener in series with the Reference to reduce the cathode voltage within specification limits will work.

Hope this helps?

David.

0 Keshav Raj over 3 years ago in reply to David Baba

Prodigy 170 points

Hi David,

Thanks for your help.

Cheers,

Keshav

0 Keshav Raj over 3 years ago in reply to David Baba

Prodigy 170 points

There is one further question I have, but rather trivial. The top of the resistive divider that controls the Vref voltage should be at the cathode of the LMV431 correct?

Cheers,

EDIT: I will make this a related question instead.

+1 David Baba over 3 years ago in reply to Keshav Raj

TI__Mastermind 28660 points

Hello Raj,

No, the top FB resistor should be placed as shown in the application note referenced above. You need the resistors positioned in a place the monitors the voltage you wish to regulate. Thanks.

David.

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LM5117: CC/CV Configuration at high voltage