LM5145: UVLO function with IBB configuration

Taketo Sato

Genius 9475 points

Part Number: LM5145
Other Parts Discussed in Thread: TLV6713

Hello team,

I want to use LM5145 with inverting buck boost configuration; Vin = +26V, Vout = -43V.

In this case, can we set UVLO by resistors, like datasheet figure8-3?

My target is Vin(on) = +20V and Vin(off) = +18V.

I would appreciate if you could advise how to consider UVLO with inverting buck boost configuration.

Best regards,

over 3 years ago

0 Timothy Hegarty over 3 years ago

TI__Mastermind 49947 points

Sato-san,

Please see this app note snva856 for more detail on level shifting for the UVLO circuit.

Regards,

Tim

https://www.ti.com/lit/snva856

0 Taketo Sato over 3 years ago in reply to Timothy Hegarty

TI__Genius 9475 points

Hello Tim-san,

Thank you for the comments.

snva856 includes level shifter information for EN but it has only short description for UVLO.

Could you please let me know how we can use TLV6713 for UVLO? It would be helpful if you could share simplified schematic for reference.

What customer would like to do is below.

Vin(on)=+20V, Vin(off)=+18V with condition of +26Vin and -43Vout.

Best regards,

0 Timothy Hegarty over 3 years ago in reply to Taketo Sato

TI__Mastermind 49947 points

Sato-san,

You can use the TLV6713 comparator with 400mV reference (falling threshold) and use a level shifter (see Fig 10b in app note snva856) to interface to the EN/UVLO pin of the LM5145.

However, the hysteresis is only 5.5mV (1.35%) or 270mV on a 20V input -- not the 2V as required. You need 10% hysteresis.

Regards,

Tim

Power management

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LM5145: UVLO function with IBB configuration