LM5177: LM5177:

Hi Roy,

thanks you for using the E3E forum.

Depending on the Vin to Vout ratio different requirement are given for the Boost and the Buck mode. So you need to select the more critical value of the two modes.

May you can direct me to the two location where you have found the mismatch in the formulas.

Best regards,

 Stefan

here I attached some inductor formula for buck boost converter that are given by TI

Here two value of inductor we find and which one i will choose and why ?

Hi Roy,

as the formula show the inductor should be greater then, so the big of the two calculated values.

Please note: you can also use the quickstart calculator tool (excel based) which you can find on the product page.

Best regards,

 Stefan

From here two inductor value is calculated and according to you i can choose 5.91 micro H , but here choose 3.3 micro H.

i go through excel sheet  also , but in excel sheet K is taken for buck mode is 80 % and boost mode is 20 to 40 % .

but in above replay it written 20 t0 40 % we can take

Hi Roy,

there is always the task to balance out what is most important for the design.

In this case it was decide to support up to a very high voltage but efficient at ~ 12 V and lower inductor size was set to be more important.

Setting deepest Boost to 20-40% is a good starting point but it also depends on the application and where the best performance should be reached in the whole operation range.

Best regards,

 Stefan

LM5177 can you explain me what is used  of CSA, CSB pin , details explains

Hi Roy,

this is the input of the current sense of the inductor current.

This controller uses the current control mode to control the switching therefore the inductor current needs to be measures.

A lot of device uses a shunt between the low side FETs and the GND for that but in this case it is done directly in front of the inductor.

Best regards,

 Stefan

IN this LM5177 is any OCP and OVP feature available in this IC

Hi Roy,

you can easily find this information if you search within the datasheet for "overvoltage" and "overcurrent"

Just let me know if any information is missing.

Best regards,

 Stefan

i think in LM5177 Four switch buck boost converter working principal is different from LM7175

Hi Roy,

the basic principal is identical like for all 4 switch buck boost converter. There are some difference in the control and the transition of the different modes.

Esp. in the Buck-Boost mode the switching frequency is different:

LM5175: fsw is identical at inductor for all modes

LM5177: fsw is identical at Gate of FETs for all modes

Best regards,

 Stefan

can u suggested one ic that have facility as a input AC=115 V and 400 Hz or DC=28 V one at a time and out as 5 V DC and 1 A 

This Lm5177 qualify the MIL-HDBK-217F