TPS61500: The design issu for TPS61500

Zhang Liang

Part Number: TPS61500

Tool/software:

Hi,

We use the TPS61500 for the LED drvie, the input voltage is 5V and the output voltage is 26V, the PWM frequecy is 40KHz, 3.3V, the duty is 57.5, the design is OK;

Now, we change the input voltage to 10.4V, and then the SW has no output signal waveform;

We has below solution to solve this issue:

1. Without powering off, by using software instructions to increase the PWM duty cycle to above 58.2%, normal operation can be immediately restored.

(However, it is necessary to increase the duty cycle to restore it, and decreasing the duty cycle cannot restore it);

2. Without powering off, short-circuit the enable pin to ground through hardware and restore it, with an 80% chance of the customer returning to normal;

Please kindly review below schematic diagram and advise if there are any modification for this design when we change the input voltage from 5V to 10.4V? Thanks.

2 months ago

0 Patrick Yao 2 months ago

TI__Mastermind 26370 points

Hi Liang,

What is the power on sequence of VIN and PWM?

And for the VIN voltage, did customer firstly power on with 5V and then ramp up to 10.4V? Or they directly power on with 10.4V?

Patrick

0 Zhang Liang 2 months ago in reply to Patrick Yao

Expert 2615 points

Hi Patrick,

Patrick Yao said:
What is the power on sequence of VIN and PWM?

The first Vin and then PWM;

Patrick Yao said:
And for the VIN voltage, did customer firstly power on with 5V and then ramp up to 10.4V? Or they directly power on with 10.4V?

They directly power with 10.4V.

0 Patrick Yao 2 months ago in reply to Zhang Liang

TI__Mastermind 26370 points

Hi Liang,

So has the PWM supplied after the VIN is already steady? Did they capture any waveform of the power on?

Patrick

0 Zhang Liang 2 months ago in reply to Patrick Yao

Expert 2615 points

Hi Patrick,

Patrick Yao said:
Did they capture any waveform of the power on

Please advise you need to the Vin waveform, right?

And can you kindly review our schematic diagram? please advise why we need to re enable when the power supply change from 5V to 10.4V,

And if we can use the same design when the power supply is 5V or 10.4V? thanks,

0 Patrick Yao 2 months ago in reply to Zhang Liang

TI__Mastermind 26370 points

Hi Liang,

Yes, just to confirm the VIN is really build and then PWM begin its input.

Schematically it seems fine, so I need more waveforms to analyze and locate the root cause. Thanks for your support.

Patrick

0 Zhang Liang 2 months ago in reply to Patrick Yao

Expert 2615 points

Hi Patrick,

Plesae refer to the Vin and Vout waveform, thanks.

0 Patrick Yao 2 months ago in reply to Zhang Liang

TI__Mastermind 26370 points

Hi Liang,

Will the IC restore if firstly power on with 10.4VIN and below 57.5% duty PWM (50% for example), and then increase the PWM duty to 57.5%?

And will change the PWM frequency do any help?

Patrick

0 Zhang Liang 1 month ago in reply to Patrick Yao

Expert 2615 points

Hi Patrick,

We set the PWM duty to 15% that the power on is abnormal, the above 64% is normal, there are significant abnormalities in the comparison of the results, thanks

0 Patrick Yao 1 month ago in reply to Zhang Liang

TI__Mastermind 26370 points

Hi Liang,

Will short R536 and remove R538 have any help?

Patrick

0 Zhang Liang 1 month ago in reply to Patrick Yao

Expert 2615 points

Hi Patrick,

There are no improve for this modification, so can you help to check this issue in the TI's demo, thanks.

0 Patrick Yao 1 month ago in reply to Zhang Liang

TI__Mastermind 26370 points

Hi Liang,

OK, I will run some test with our EVM and give you feedback later.

Patrick

0 Patrick Yao 1 month ago in reply to Zhang Liang

TI__Mastermind 26370 points

Hi Liang,

I have setup the EVM with similar condition, the IC still works normally. May I know if customer could also send me their layout for double check? You can send it to me through private message if customer has confidential concern.

Patrick

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TPS61500: The design issu for TPS61500