TPS563201: TPS563201-FB FB voltage is too high

switch

Part Number: TPS563201

Hi ti Team，

I have a project using TPS563201, and found that the voltage is as high as 0.81V at light load，This voltage has exceeded the specification range, as follows:

over 4 years ago

0 Edwin Zang over 4 years ago

TI__Expert 6425 points

Hi,

would you like to capture SW and Vout waveform to share to me? please share me schematic to review.

BRs,

Edwin.

0 switch over 4 years ago in reply to Edwin Zang

Genius 3760 points

Hi Edwin,

FYI

1，Schematic diagram

2，Vin=12V Vout=5V Light load SW Waveform

3，Vin=12V Vout=5V Iout =0.2A SW Waveform

4，Vin=12V Vout=5V Iout =0.5A SW Waveform

6，Vin=12V Vout=5V Iout =2A SW Waveform

0 Gerold Dhanabalan - Online Design Tools over 4 years ago in reply to switch

TI__Genius 14455 points

Is your question on the reference voltage and the voltage at the feedback pin?

If so, the Vref specification is at Vo=1.05V. In your case as Vout is 5V, and you can expect this difference from the nominal value.

Regards,

Gerold

0 switch over 4 years ago in reply to Gerold Dhanabalan - Online Design Tools

Genius 3760 points

Hi Gerold，

Yes, this voltage comes from tps563201 FB pin .

The no-load output ripple is about 130MV, why does the FB voltage exceed the specification by so much?

0 Vincent Zhang(BSR) over 4 years ago in reply to switch

TI__Expert 4795 points

Hi Switch,

The 814mV you measured is FB voltage RMS value. The FB node voltage should have ripple so the RMS value is a little bit larger than average value. You can use smallest loop to measure the waveform across the bottom feedback resistor to double confirm. The average voltage of Fb node is the Fb voltage.

Meanwhile, you can also use below method to check Fb voltage, that's what we did in final test:

1. Remove R1 and R2

2. Add external supply on FB node

3. Sweep the power supply from 0.6V to 0.9V, monitor SW waveform. When Vsupply < Vfb, SW is maximum duty cycle; when Vsupply > Vfb, SW is keeps low.

4. The voltage make SW change from maximum duty cycle to low is the Fb voltage.

0 switch over 4 years ago in reply to Vincent Zhang(BSR)

Genius 3760 points

Hi Vincent,

I want to know what is the minimum and maximum FB voltage for Vo = 1.05, Iout = 10mA Eco mode operation, the specification does not indicate

0 Vincent Zhang(BSR) over 4 years ago in reply to switch

TI__Expert 4795 points

Hi,

Let me check with my colleague and feedback to you tomorrow.

0 Vincent Zhang(BSR) over 4 years ago in reply to switch

TI__Expert 4795 points

Hi,

The minimum and maximum FB at VO=1.05, IOUT=10mA condition is 754mV / 792mV.

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TPS563201: TPS563201-FB FB voltage is too high