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Original question:

LM5170EVM-BIDIR: when use buck mode, input voltage is 48V, but the output is not 12V

LM5170EVM-BIDIR: LM5170EVM

Vishnu Maheswar
Prodigy 70 points
Part Number: LM5170EVM-BIDIR
Other Parts Discussed in Thread: LM5170

We are using LM5170 EVM as 12 V Lead Acid battery charger. (48 V i/p, 14.5 V o/p)

We need to set the current limit as 60 A and keep the voltage regulated around 14 V (keeping it safe within battery voltage specs).

Is there any way to set the o/p current  (using ISETA pin ) and still keeps the output voltage regulated around 14 V?

  • 0
    TI__Guru* 78200 points

    Hi Vishnu,

    Thank you for posting.  I just answered your other post.  You can only regulate the voltage or current, but not both at the same time, because only one loop can be in control but not both.  To charge the battery, what you need to do is to limit the ISETA as mentioned in my answer to your other post, and use the voltage loop to limit the max voltage to be at 14V (The EVM voltage setting is at about 14.5V).

    Hence, when the battery voltage is less than the targeting voltage, the circuit will run in constant current limited by the ISETA clamp, which is set by the resistor divider of R86 and R81.   When the battery voltage is close to the setting voltage, the voltage loop will reduce the ISETA to maintain the voltage not exceeding the setting point, namely you regulate the output voltage at it.  All these functions have been covered by the EVM circuit when you use output voltage loop control circuit  by closing the following jumpers:  J34, J35. J36, and J37.

    Hope this clarifies. 

    Best Regards,

    Youhao Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    Prodigy 70 points

    Hi Youhao,

    Thank you so much for the quick response.

    I think we can go ahead with the way you proposed.

    Once again than you so much for the instant solution provided.