TPS65266: TPS65266RHBT

Jay Kevalramani

Part Number: TPS65266

Tool/software:

Hello ,

We have used TPS65266RHBT multi-switcher IC to meet specific parameters for our project. Here are the requirements:
Input Voltage: 5V
Output1: 0.9V @ 3A
Output2: 1.5V @ 1.5A
Output3: 1.8V @ 1.5A

for which after Load testing results

1) For 0.9 V at low load

Vin(V)	5
Iin (A)	0.15
Vout(V)	0.79
Iout(A)	0.502
Total Load(ohm)	1.574
Input power(watt)	0.750
Output power(watt)	0.397
Efficiency(%)	52.87733333

For 1.5V at low load

Vin(V)	5
Iin (A)	0.14
Vout(V)	1.48
Iout(A)	0.302
Total Load(ohm)	4.901
Input power(watt)	0.700
Output power(watt)	0.447
Efficiency(%)	63.85142857

we have observe very low efficiency that doesn't meet our requirement as we want more than 90% efficiency

We have also confirmed the design before fabrication in these Thread: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1350417/tps65266-tps65266rhbt/5166714#5166714

I'm attaching the snapshot of schematic and layout please suggest us required changes to meet our expectations.

over 1 year ago

0 Lucia Gao over 1 year ago

TI__Mastermind 30421 points

Hi Jay,

Pls kindly let me check and get back to you during these days. Thank you!

BRs

Lucia

0 Jay Kevalramani over 1 year ago in reply to Lucia Gao

Prodigy 30 points

Hi Lucia,

Thank you for your message. I understand you need some time to review. If possible, could you please provide your feedback at your earliest convenience? Your prompt response would be greatly appreciated.

Best regards,
Jay

0 Lucia Gao over 1 year ago in reply to Jay Kevalramani

TI__Mastermind 30421 points

Hi Jay,

Pls try below:

(1) Check whether your efficiency test method is good. One way is that you can check TPS65266EVM to see whether you can get 90% efficiency. And when you test 0.9V rail, did you disable other power rails (EN pull down)? And only see efficiency low with 0.9V rail and 1.5V rail? How about 1.8V rail?

Performing Accurate PFM Mode Efficiency Measurements (Rev. A)

(2) Pls capture the waveform of LX1 and LX2 to double confirm if you see any unstable like multi-pulse?

Thanks!

BRs

Lucia

0 Jay Kevalramani over 1 year ago in reply to Lucia Gao

Prodigy 30 points

Hi Lucia

Thank you for quick response, As you say to isolate the two rails and to check the efficiency of single rail. I've done that and here are the Results below for 0.9V and also for 1.5 and 1.8 (Without isolation) . We are more concern about 0.9V rail as its efficiency is very less please help if any changes are required.

1) 0.9V Rail With Isolation

0.9V	Low Load	typical Load	High Load
Iin (A)	0.11	0.36	0.66
Vout (V)	0.915	0.914	0.914
Iout (A)	0.502	1.502	2.502
Efficiency(%)	83.51454545	76.26	69.29781818

2) 1.5V Rail without Isolation

1.5V	Low Load	typical Load	High Load
Iin (A)	0.12	0.12	0.36
Vout(V)	1.51	1.51	1.51
Iout (A)	0.303	0.303	1
Efficiency(%)	76.255	80.32	83.88888889

3) 1.8V Rail without Isolation

1.8V	Low Load	typical Load	High Load
Iin (A)	0.22	0.43	0.65
Vout(V)	1.82	1.82	1.82
Iout(A)	0.502	1	1.502
Efficiency(%)	83.05818182	84.65116279	84.112

Best Regards,

Jay

0 Lucia Gao over 1 year ago in reply to Jay Kevalramani

TI__Mastermind 30421 points

Hi Jay,

Where did you test the input voltage and output voltage? For example, did you measure the Vout from the output capacitor?

Thanks!

BRs

Lucia

0 Jay Kevalramani over 1 year ago in reply to Lucia Gao

Prodigy 30 points

Hi Lucia,

The Output voltage is measured across the capacitor C17 ,C25,C35 respectively for the particular rail and the Input Voltage is being provided through DC supply at the power section of PCB

Best Regards,

Jay

0 Lucia Gao over 1 year ago in reply to Jay Kevalramani

TI__Mastermind 30421 points

H Jay,

When you are measuring the efficiency, I would recommend you can measure the input voltage from the input capacitor which is closer to VIN pin and measure the output voltage from the output capacitor to get more accurate result. If measuring from the actual power supply or the load, the effect of the wire loss could not be ignored especially with heavier loading. Thanks!

BRs

Lucia

0 Jay Kevalramani over 1 year ago in reply to Lucia Gao

Prodigy 30 points

Hi Lucia ,

The Input voltage is constant which is 5V which we are observing and also the output voltage is being measured at the output capacitor by keeping the length of the wire as short as possible to reduce the loss.

Best Regards,

Jay

0 Lucia Gao over 1 year ago in reply to Jay Kevalramani

TI__Mastermind 30421 points

Hi Jay,

Pls kindly let me check and get back to you during these days. Thank you.

BRS

Lucia

0 Jay Kevalramani over 1 year ago in reply to Lucia Gao

Prodigy 30 points

Hi Lucia,

Your prompt feedback would be greatly appreciated.

Best Regards,

Jay

0 Lucia Gao over 1 year ago in reply to Jay Kevalramani

TI__Mastermind 30421 points

Sure.

BRs

Lucia

0 Lucia Gao over 1 year ago in reply to Lucia Gao

TI__Mastermind 30421 points

Hi Jay,

Since it's integrated MOSFET device, if you would like to further improve the efficiency with heavy load, I would recommend you can try the inductor with higher inductance like 3.3uH and lower DCR to see if there is any improvement.

Thank you!

BRs

Lucia

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TPS65266: TPS65266RHBT