Using the external clock ,default-freqency setting use the RT resister

masa0301

Other Parts Discussed in Thread: TPS54340

Could you tell me RT resister at TPS54340.

I checked below.

Design the external synchronization circuit
such that the default-frequency set resistor connects from the RT/CLK pin to ground when the synchronization
signal is off.

In this case default-freqency setting use the RT resister, how much accuracy do you are allowed.

masa

over 11 years ago

0 JohnTucker over 11 years ago

TI__Guru**** 191445 points

What frequency are you trying to operate at? Eq. 5 on page 13 of the datasheet gives the equation for calculating the RT resistor.

0 masa0301 over 11 years ago in reply to JohnTucker

Intellectual 960 points

John

I will set 635kHz、615kHz.

I know this calculation formula.

My question is if I set 600kHz, Do you allow RT resister set for example 500kHz ?

Can you accept how much accuracy of the external clock,

masa

0 JohnTucker over 11 years ago in reply to masa0301

TI__Guru**** 191445 points

The external frequency synchronization is done via PLL. I think the actual switching frequency vs sync frequency is exact. Usually you should set the RT frequency to be as close as possible to the sync frequency. there is no hard requirement for this as far as the PLL is concerned, but the inductor ripple current will vary proportionally to the switching frequency.

0 masa0301 over 11 years ago in reply to JohnTucker

Intellectual 960 points

Hi Jonh

Thank you for your quick reply!

I understand need the set close to external clock.Because of inductor ripple current will vary proportionally to the switching frequency.

masa

0 priyank mani over 9 years ago in reply to JohnTucker

Intellectual 290 points

Dear John,

I need to know the best suitable frequency for the TPS54340 @ 5V / 3.5Amp load ,. so that there is n issue of EMI/EMC.
If you can send me some relevant application note . that will be awesome.

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Using the external clock ,default-freqency setting use the RT resister