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LM27762: IC which will provided boosted dual supply from 0.7V of 3.3V with integrated LDO

TapasXplore
Expert 1280 points
Part Number: LM27762
Other Parts Discussed in Thread: TPS61220, , LM27761, TPS65133

Hi,

I am using single cell NiMH cell (0.7V) to boost the power to 3.3V using TPS61220 (Low Input Voltage, 0.7V Boost Converter), the intended application is for audio amplifier, hence positive and negative supply is required (+/-1.5V) with integrated LDO. My bet is on LM27762 (Low-Noise Positive- and Negative-Output Charge Pump With Integrated LDO). But I am confused between LM27761 (Low-Noise Regulated Switched Capacitor Voltage Inverter) or TPS65133 (Split-Rail Converter, ±5V, 250mA Dual Output Power Supply).

Is there any integrated circuit which will boost the voltage from single cell NiMH (0.7V) to 3.3V and at the same time provide dual supply output with integrated LDO. Any suggestions will be appreciated. 

Regards,

Tapas

  • 0
    TI__Guru**** 150610 points
    Hi Tapas,

    Your current solution is likely the best you will find. It is difficult to make a boost operate from a single cell battery and then follow it with an inverter and LDOs in the same package.
  • 0 in reply to Chris Glaser
    Expert 1280 points

    Hi Chris,

    I will use TPS61220 for boosting (from 0.7 V to 3.3V) After that there is requirement for clean positive and negative supply (+/-)  for op-amp. Just to mention I am not using any microcontroller in the circuit. 

    So one of the following (LM27762 or LM27761 or TPS65133) IC will required after previous boost stage.  According to power house blog by Antony Pierre Carvajales from TI, capacitive and inductive topologies are better than virtual ground. If we compare output ripple and noise as a parameter then capacitive topoplogy will emerge as a winner.   

    Can you help between choosing LM27761 or LM27762.  

    Below, I have attached screenshot taken from datasheet. It mentions topology of LM27762 as Buck/Boost and of LM27761 as Inverting. I am already using boost IC TPS61220 hence Buck/Boost is not required (this is what I think, you can correct me if I am wrong) Can you explain why Vin (Min/Max) of both the IC's are same, so whats the advantage of having buck/boost in LM27762. And why LM27762 is not providing negative supply as mention below (Vout min) in the screenshot. 

    According to my my observation LM27761 is best fit for me, I need your opinion. What difference will it make if I choose LM27762 instead of LM27761.

     

    Regards,

    Tapas

  • 0 in reply to TapasXplore
    TI__Guru**** 150610 points
    The LM27762 is basically a LM27761 with a positive LDO added. It sounds like you need a positive LDO, so the LM27762 would be best.

    See my blog: e2e.ti.com/.../one-family-the-right-inverting-charge-pump-for-you