Post Go back to editing

Paralleling LT8642S with RT

Category: Hardware
Product Number: LT8642S

To whom it may concern,

I connected LT8642S in parallel as shown below. You can find it in datasheet, Page-22. However, the datasheet did not clearly say how to connect pin RT, which is clock/frequency setting.

From the simulation (LTSpice 24), I had a single RT for both devices (Master/Slave) and the simulation worked fine for 3.3V and 1.8V configurations as expected in Forced Continuous Mode. However, when I built the same circuits on PCB, the 3.3V worked as expected but not 1.8V. The 1.8V stucked in Burst Mode Operation.

From the senior power engineer, he suggested to have 2 seperate resistors for RT pins even in paralleling. It worked!

My question is: Why did it NOT work for 1.8V but worked for 3.3V? Do you have any clear explaination for RT pin in Paralleling? If you have any White Paper about RT in Paralleling, please point me to that direction.

Thank you.

  • As a general rule of thumb, use a discrete/unique frequency-setting resistor for each converter unless explicitly stated otherwise in the datasheet. 

     

    I can't say for certain why the implementation worked in 1.2V and not the 3.3V case without knowing more about your implementation.  One possibility is that the loading on the 1.2V rail is less, which would allow the part to operate in burst mode. 

Before You Switch


Switching languages will make ADI Explorer unavailable. Resume your session by switching back to English and reopening ADI Explorer.