Buck - Boost design using LTC3112

I see LTC3119 more opt for this.

Please answer for Questions 2 & 3 keeping LTC3119 as regulator.

Hi,

 LTC3112 starting operating voltage is 2.7V so it might not be apt for the application.

Given the operating range for the application, LTC3119 is a suitable part. Since the boost ratio is not much in this case, LTC3119 should be able to support the required max load even while in boosting. For your reference, on page 9 of the datasheet, there are efficiency graphs for various output voltage wrt load current at different input voltages. This would give you an idea of the max current capability at a desired input voltage.

 LTspice has an application circuit for LTC3119 in its library. First add component LTC3119 in the LTspice schematics page --> After adding right click the model --> Select first option i.e. 'Open this macromodel's test fixture'. This will open the application reference circuit which you can update and simulate based on the requirement. Page 27 and 28 of the datasheet has few application circuits for 3.3V output voltage. You can use these values to simulate the circuit.

Alternatively, we have demo board DC2129A available for LTC3119. You can use the demo board for your application after configuring it for the requirement.

Let us know if you have further questions.

Thanks 

Hi,

 LTC3112 starting operating voltage is 2.7V so it might not be apt for the application.

Given the operating range for the application, LTC3119 is a suitable part. Since the boost ratio is not much in this case, LTC3119 should be able to support the required max load even while in boosting. For your reference, on page 9 of the datasheet, there are efficiency graphs for various output voltage wrt load current at different input voltages. This would give you an idea of the max current capability at a desired input voltage.

 LTspice has an application circuit for LTC3119 in its library. First add component LTC3119 in the LTspice schematics page --> After adding right click the model --> Select first option i.e. 'Open this macromodel's test fixture'. This will open the application reference circuit which you can update and simulate based on the requirement. Page 27 and 28 of the datasheet has few application circuits for 3.3V output voltage. You can use these values to simulate the circuit.

Alternatively, we have demo board DC2129A available for LTC3119. You can use the demo board for your application after configuring it for the requirement.

Let us know if you have further questions.

Thanks 

OK,

I will design the required configuration using LTC3119 and come back.

Thanks

I see a graph for Boost ratio vs Output current in Page 10.

Is the same graph available for Output 3.3V. or can we use this same graph for 3.3V output case also.

Hi,

That graph is  for Vout=12V. Since boost ratio for your application very small (boost from 2.5V to 3.3V) , the part should be able to support the max load current(1A). If you wish to know the max current for 3.3V out at 2.5V input ,you can refer the first three efficiency vs load current graphs at page 9 for 3.3V out at different input voltages.

Thanks