Buck converter and LDO usage

Hello Vignesh,

As John Tucker mentions, The TPS5401 is a reasonable device to begin your search with.

The efficiency of a switcher can be very good over a wide load range, depending on the modes of operation.
There is very little change from 0.3A to 0.1A ~90% in this 12Vin 5Vout, TPS5401 datasheet example.

TPS5401 has High Efficiency at Light Loads With a PulseSkipping Eco-mode™ Control Scheme

              

LDO current : 0.1A
               LDO efficiency is always Vout/Vin,  3.3Vout/30Vin = 11%

For an LDO to be effective, the load current needs to be much much less, falling off the left edge of the efficiency graph shown.
If indeed your currents are 0.3A to 0.1A then a high efficiency switcher with light load optimization will be your best solution.

 

Here is a Webench design for TPS5401 ‑ 20V-30V to 3.30V @ 0.3A

               https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=63B7EE26E6CD8AE4

The efficiency is very good at low load currents. Better than an LDO could achieve.

 

              

 

 

Next, here is a Webench design for LMR23610 ‑ 20V-30V to 3.30V @ 0.3A

               https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=EB345E3483874BB4

 

The efficiency is excellent at very low load currents.
This device has improved light load efficiency, better than the TPS5401.

               (note the Log-Scale on the lower graph)

              

 

 

There are also reference designs for E-Bike type of applications.
These will provide a good baseline for your design to follow.

http://www.ti.com/solution/battery-pack-ebike-escooter-light-electric-vehicle-lev?variantid=30605&subsystemid=31053

http://www.ti.com/solution/ebike_hmi?keyMatch=bike&tisearch=Portal%20Search%20Application-&INTC=Portal%20Search%20Application-

http://www.ti.com/solution/e_bike?keyMatch=bike&tisearch=Portal%20Search%20Application-&INTC=Portal%20Search%20Application-

 

 

Vignesh,

TPS5401 is probably a better fit for you than TPS54061. TPS54061 is only rated to 0.2 A and you stated above that you require up to 0.3 A. Also TPS5401 has lower high side FET on resistance and a lower unit price than TPS54061.

Thanks John,

Now we are planning to design 24V,36V BMS. for 24V pack input voltage 20V to 30V and for 36V pack input voltage 32V to 43V. We are targeting to use one buck converter for both application in order reduce the line item in our BMS design. so TPS5401 absolute max is 42V it won't fit or 36V BMS ( 43V is pack max voltage) and our current roughly about 0.2 to 0.3A (not confirmed) so we are exploring better match for our application. please give your suggestion on this

Thanks,
Vignesh

Vignesh,

For lowest cost I would look at TPS5460A:
www.ti.com/.../TPS54060A

For lowest Iq at slightly higher cost LM36006:
www.ti.com/.../LMR36006