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LM26480-Q1: LM26480-Q1 Sequence with EN and some questions

Part Number: LM26480-Q1

Hi Team, 

My customer is interested in LM26480-Q1

The required output sequence is below;

  • Vin 3.3V -> 1.8V  (Back1)
  • Vin 3.3V -> 1.1 (Back2) 
  • LDO1 3.3 -> 2.8 
  • NPOR (1.8V) 

Under the above condition, can ENSW2 be enabled by 1.8V (Back1)? 

Or, can ENLDO1 be enabled by 1.1V (Back2)? 

2) Raising time of each Vout 

Would you please let me know each of raising time? the details is below.

What the raising time of Back1 if it set to 1.8V? and Back2 is 1.1V, LDO1 is 2.8?

Regards, Naoki Yada

  • Yada-san,

    The regulators are not programmable, they are only enabled with external pins. The customer should be able to connect Buck1 to ENSW2, and Buck2 to ENLDO1. Enable high level is 0.7xAVDD, so the Buck1 and Buck2 voltage may not be high enough. If LDO2 is un-used, can the customer enable LDO2 by default at 3.0V and use this as a logic level. Buck1 and Buck2 voltages can drive small NFET transistors with VT<1V to Enable the next rails in sequence.

    Will this work?

    The buck regulators have soft-start after VIN is >2.8V. Soft-start increases the current limit from 250mA, to 500mA, to 950mA, and finally to 2A in what appear to be 100uS increments according to Fig. 30 and Fig. 31 in the datasheet. Actual rise time of the regulator will be dependent on load and capacitance.

    NPOR only seems dependent on Buck1 and Buck2, not LDO1.