TPS61165: Voltage drops from 15V - 0V on power up

Rangarajan Krishnamachari

Part Number: TPS61165

Hello,

I am debugging a legacy design where we have the ctrl signal connected to 1.8V, VIN - 5V and rest of the circuit follows your recommended schematic as shown below. Previously, I was measuring 0V at the output but then that was caused by the reverse polarity of the Diode on CTRL pin and after fixing that issue, I am measuing the correct voltage on ctrl pin. I am not sure what might be causing the voltage drop from required voltage to zero. Any recommendations on what might be causing this issue?

Thanks

Ranga

over 4 years ago

0 Charles-Chen over 4 years ago

TI__Genius 11836 points

Hi Rangarajan,

Proper engineer has been assigned to look at this and will reply to you soon.

0 Sean Zhou over 4 years ago

TI__Mastermind 22745 points

Hi Sir,

I'm not very clear about your question, you mean you have measured the 0V at the output when Vin=5V and CTRL pin is 0V? this is very strange since for boost topology there is always a power path even there is no switching.

And you have mentioned that you have fixed the issue, what you have done with the issue?

BTW, what's your reason of using U5 part?

Regards

Sean

0 Rangarajan Krishnamachari over 4 years ago in reply to Sean Zhou

Intellectual 280 points

Hi Sean,

The question is any idea why I might see the voltage at DAB_BLD_A would be reducing from 15V - 0V?

I measured 5V at output not 0V as previously mentioned when ctrl was @ 0V. When I fixed the error on our board with the diode orientation on Ctrl pin. I measured high voltage at output 15-18V but see this voltage dropping rather than being fixed at that voltage.

U5 is a buffer circuit and part of our legacy circuit.

Thanks

Ranga

0 Sean Zhou over 4 years ago in reply to Rangarajan Krishnamachari

TI__Mastermind 22745 points

Hi Ranga,

From your description, it seems that the reason is the diode connected to "CTRL" pin. It seems that this Diode has clamped to a low voltage when you connect wrong. Now you have fixed the question, so is there any other question? Thanks.

Regards

Sean

0 Rangarajan Krishnamachari over 4 years ago in reply to Sean Zhou

Intellectual 280 points

Hi Sean,

I fixed the diode before posting the question. Before the diode was fixed the output was fixed at 5V but with the fix ,it actually goes to the required high voltage 15V but for some reason does not stay at 15V and drops to 5V again. I am trying to figure out what might be causing this drop? Any suggestions?

Thanks
Ranga

0 Sean Zhou over 4 years ago in reply to Rangarajan Krishnamachari

TI__Mastermind 22745 points

Hi Range,

I don't have more commons, please let me know if you have any update, thanks.

Reagrds

Sean

0 Rangarajan Krishnamachari over 4 years ago in reply to Sean Zhou

Intellectual 280 points

Hi Sean,

I purchased the TPS61165 EVM kit and made sure it worked fine before I tried to recreate my issue. I was able to create similar drop in VLED+ voltage when JP2 jumper is disconnected. My question is that if it is possible the IC is damaged on my board?

0 Sean Zhou over 4 years ago in reply to Rangarajan Krishnamachari

TI__Mastermind 22745 points

Hi Sir,

When you disconnect the JP2, have you connect the LED load between J3 and J4 and short R4? Since you have disconnected all the load, the voltage on J3 should be close and lower to Vin.

Regards

Sean

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TPS61165: Voltage drops from 15V - 0V on power up