• TI thinks resolved


For a Master-Project from my University we have to power three actors in a 3D stereo lithographic printer.

We would like to use the IC LM22676MRE-5.0/NOPB with an Input of Vin: 12V and we need Vout: 5V/4,5A.

In the Datasheet they say the CL Current Limit is Min: 3.3A and Max: 5.5A. Is it possible to get 4,5A with the normal configuration?

Or do we need a special configuration? Many thaks in advance!

Benjamin Mattmüller

  • Benjamin,

    LM22676 is a nominal 3 A output.  LM22676 may enter current limit at output currents as low as 3.3 A.  For 4.5 A output TPS54620 might be a good choice for you.  I'm sure there are many other options.  I would suggest you try the Webench on line tool:

    You can enter your requirements and Webench will return a list of possible options by Module, Converter or Controller.  Let us know what you think

    John Tucker

    BSR-CCP LV/MV DC/DC Applications

  • In reply to JohnTucker:

    Hello Tucker, thanks for your reply. The problem which we have is, that we already routed our board with the using of the LM2672 (1A). Our power consumption raised up to 4,5A but the board is already fixed. The LM22676MRE-5.0 would fit to the same pins which we configured. In the datasheet I found  a formula (12 inductor) were you can determine the coil for user application. In my result I have to use an inductor with 4.3µH to get 4.5A.... is that possible? 

  • In reply to user4222980:

    The LM22676MRE-5.0 uses peak current limit.  During the high side switch on time the switch current is rising.  If it reaches the current limit threshold during the on time, the the high side switch is turned off and the low side switch is turned on, limiting the duty cycle to less than required for proper regulation.  So the maximum load current is equal to the current limit threshold minus one half the peak to peak inductor current,   See section 7.4.1 in the datasheet which explains this and contains the formula for you to calculate the maximum load current for your design,  For Vin = 12 V, Vout =5 V and Lout = 4.3 uH:

    ILp-p = 1.36 A

    Current limit is 4.2 A nominal and 3.35 A minimum over temperature so your maximum load current = Icl - ILp-p / 2 = 3.52 A nominal or 2.672 A worst case.  It is best to design for the worst case.  You can increase the maximum load current by increasing the inductor value, but you will never get a reliable 4.5 A.

    John Tucker

    BSR-CCP LV/MV DC/DC Applications