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ADS1284: Ways to increase efficiency

Ying Rui Sebestian Tan
Prodigy 125 points
Part Number: ADS1284
Other Parts Discussed in Thread: LM27761, TPS7A05

My customer is using an ADS1284.

Presently, he is using an LDO (TPS79325DBVR) to generate the +2.5Volt rail from the 3.0Volt rail that I have for the digital side of the electronics, and then used a Charge Pump (TPS60400DBV) to invert the 3.0Volt rail, then followed this with an LDO (TPS72325DBVT) to get the -2.5Volt rail. The best efficiency he can get for the +2.5Volt rail (assuming that we are starting from 3.0Volts) is 83%. It is worse for the negative rail because of the efficiency of the charge pump device. 

He is asking whether is there any other options to generate the +/-2.5Volt rails efficiently. 

Sebestian 

Field Applications Associate  

 

 

  • 0
    TI__Guru*** 147250 points

    Hi Sebastian,

    What is the load current on the positive and negative 2.5V?

    We have the LM27761 as an integrated inverting charge pump + LDO.  

    For the positive rail, the easiest way to increase the efficiency would be to use a DC/DC.

  • 0
    TI__Mastermind 34755 points

    Hi Sebastian,

    The negative linear regulator the customer has chosen is at the bottom of the IQ current draw range, so that will be challenging to improve upon.  The customer may wish to change the positive linear regulator to the TPS7A05 which comes in 2.5V fixed versions.  The ground current for the TPS7A05 is orders of magnitude less than the current selection by the customer (TPS79325DBVR).  As Chris asked, it may be more efficient to use a switching converter if the positive rail needs to provide a lot of current.  If the customer could provide the load information, we could further assess the best path forward.

    Thanks,

    - Stephen