LM27762: LM27762DSSR Schematic review

Hi any updates?.Please provide your comments for the above

My input voltage range is around 3.3V

Hi Nivethitha,

The +ve output rail is achieved by using an LDO between input and output. So it won't be possible to get a +5V from a +3.3V input.

For the negative rail, the position of the R99 (95.3K) and R101 (56K) resistors seem to be swapped.

Best regards,

Varun

Thanks for the comments varun. Do you suggest any chargepump for +5V and -3.3V supplies?

Same part??

Hi Nivethitha,

Do you have only a 3.3V input supply? Or is there a higher rail available?

Best regards,

Varun

Yes..only 3.3Vwill be available.  any solution possible???

Hi Nivethitha,

I think you would need a boost converter to convert 3.3V to 5V. Can you please create a new thread for recommendations on boost converters?

The LM27761 can then be used to create the -3.3V using the 5V from the boost converter. It's better to run the LM27761 using the 5V supply rather than 3.3V supply to take care of the built in charge pump voltage loss and LDO drop out voltage.

Best regards,

Varun

Thanks for the suggestion varun.

Is any charge pump which does not use LDO output , but supplies both -3.3v and 5v(3.3V input should be pumped up) available?

Hi Nivethitha,

We don't have other dual rail charge pumps. However for the 3.3V in to 5V out you can consider the TPS60151,  LM2775, LM2750.

For the -3.3V output, you could consider the TPS60400 and LM2776 (both unregulated: VOUT= -VIN). If you use the +3.3V rail as input, the absolute value  of the output voltage will be slightly lower than 3.3V due to the losses across the charge pump resistance. The losses increase with output current.

The alternative would be to use +5V as the input and use a regulated charge pump like LM27761 (with integrated LDO) to obtain an exact -3.3V.

You will need to calculate if the max load currents of the charge pumps you use are high enough for your application.

Best regards,

Varun

Could you suggest a high efficient 5V boost converter which might have load current of around 100mA and Negative voltage converter or Charge pump to give -3.3V load current 10mA.

Our architecture for your reference ,

Do you suggest any? 

1) What will be the best efficient configuration?

2) Boost converter for 5V?

3) Charge pump for -3.3v?

the system should be efficient and current drawn from the battery shall be low as possible

Hi Nivethitha,

Boost converters belong to a different product line. You would have to create a separate thread so that the right product line is tagged to support you on boost converters. 

In terms of efficiency, for the -3.3V rail, it would be best to use TPS60401 running from +3.3V input. 

The output voltage will be around -3.2V with 10mA of load current.

Best regards,

Varun