TPS54260-Q1: TPS54260QDGQRQ1

ABDUL RAHUMAN

Part Number: TPS54260-Q1

Tool/software:

Hi Team,

We are currently facing a CISPR 25 Class 3 CE compliance failure. During testing, we observed that the failure frequencies are directly correlated with the switching frequency of the TPS54260QDGQRQ1, which operates at a switching frequency of 336 kHz.

Further investigation revealed that when a USB pendrive is connected—drawing less than 5 mA—the TPS54260QDGQRQ1 enters pulse skip mode. We suspect that this operating mode is causing the emissions that lead to CE failure.

Our customer requires the system to pass CISPR 25 Class 3 testing even when a USB pendrive is connected. Could you please advise us on how to resolve or mitigate this issue?

2 months ago

0 EricLee 2 months ago

TI__Guru 58941 points

Hello Abidul

Please test again following this

Step1. Remove USB pendrive, add 5 mA equivalent resistor load, and measure CE again.

Step2. Add RC snubber (10ohm + 470pF) at PH node, and measure CE again .

-EL

0 ABDUL RAHUMAN 2 months ago

Prodigy 30 points

Hi EricLee,

I am adding a snap of our circuit. We already have 10E 1500pF snubber circuit. After adding a 5mA equivalent load resistor the IC working in the DCM mode. I am attaching the switching frequency when 5mA load added. As per the datasheet, the TPS54260QDGQRQ1 will operate FPWM when the load current is greater than 337mA. Is DCM mode give the good results in CE? There is any option to operate the TPS54260QDGQRQ1 in FPWM mode at Pendrive connected case.

0 EricLee 2 months ago in reply to ABDUL RAHUMAN

TI__Guru 58941 points

Hello Abdul

Please make it sure that one of C203,204,205 capacitors are physically located between #2 pin and the anode connection of D20.

-EL

0 ABDUL RAHUMAN 2 months ago in reply to EricLee

Prodigy 30 points

Hi Eric lee,

I am attaching the our PCB placement below

Is there anyway to operate the TPS54260QDGQRQ1 in PWM mode when a pendrive is connected?

0 EricLee 2 months ago in reply to ABDUL RAHUMAN

TI__Guru 58941 points

Hello Abdul

In order to make the converter operates in CCM at light load, switching frequency should be increased and the inductance of the power inductor should be increased together.

In there any input EMI filter ?

-EL

0 ABDUL RAHUMAN 2 months ago in reply to EricLee

Prodigy 30 points

Hi Eric,

We have the Pi filter in input 12V side.

How to increase the switching frequency?

0 EricLee 2 months ago in reply to ABDUL RAHUMAN

TI__Guru 58941 points

Hello Abdul

Please reduce R178, R181 values in order to increase the switching frequency.

Please populate ~ 10u-20uF in parallel with C259 and check if any EMI improvement.

-EL

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TPS54260-Q1: TPS54260QDGQRQ1