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Looking for device

Renan Santos Adriano
Genius 17740 points
Other Parts Discussed in Thread: LM5180, LM5017

Hello Team,

My customer is designing an SMPS application that is a bit different and struggling to find a chip that will work.  Low power (about 1 watt), half-bridge, the tiny overall size (10mm).  

So they need 
-wide input voltage range (3.0v to 36v) negotiable
-internal switches (1-2A) high-side and low-side
-PWM controller, 
-adjustable frequency (400KHz-1MHz) negotiable 

Desirable features
-soft start
-pulse by pulse current limit
-OV/UV lockout

1) Buck controllers seem likely, but it is not clear if switch current can be positive AND negative (half bridge current is symetrical positive and negative).  Will the low side switch SINK current?  

2) Is there a half-bridge controller appropriate for 1W power levels?  

Regards
Reanan

  • 0
    TI__Mastermind 28660 points

    Hello Reanan,

    A buck converter will not work for a half Bridge topology.  The logic of a half bridge is that of an interleaved isolated buck.  In other words the D period is split between the HS and the LS FET; D1 and D2 respectively.  The 1-D1 and 1-D2 periods occur when both HS and LS FETs are off.  Compare to the Buck (obviously non isolated) with the D period occurring when the HS FET is on and the 1-D period occurring when the LS FET is on.  You will need to us a dedicate Half Bridge converter or a push pull for this application.

    However, if your power requirement are only 1W, I suggest you consider the Fly-Buck topology or a Fly-Back topology.  Please consider the LM5017 or the LM5180 respectively,  Hope this helps?

    David Baba.