LM3697: Seeing 5V on the current sink

Cameron Wutzke

Part Number: LM3697

Tool/software:

Hey Folks!

We are driving a string of 7LEDs, about 24Vout . Our sink pin is reading 5V, we think some type of register setting is off... Have you seen this before?

Our fear is burning some unnecessary power on the 5V pin on the sink

Thanks,

Cameron

10 months ago

0 Patrick Yao 10 months ago

TI__Mastermind 34820 points

Hi Cameron,

What is their register setting of 0x1A?

Patrick

0 Cameron Wutzke 10 months ago in reply to Patrick Yao

TI__Expert 3602 points

value 0x02

0 Patrick Yao 10 months ago in reply to Cameron Wutzke

TI__Mastermind 34820 points

Hi Cameron,

May I have a look at their schematic as well? Please also check the register setting of 0x19.

Patrick

0 Cameron Wutzke 9 months ago in reply to Patrick Yao

TI__Expert 3602 points

Hey Patrick!

I got some more data:

Register 0x19 is/was set to 0x03 (00000011b) – but I think it should be set to 0x01 (00000001b), so we are making that change now; please confirm that my understanding is correct?

I will email relevant PCB schematic

the display backlight has a single string of (7) LEDs with total Vf ≈ 19.25V

0 Patrick Yao 9 months ago in reply to Cameron Wutzke

TI__Mastermind 34820 points

Hi Cameron,

Yes, please set the 0x19 register to 0x01, let me know if this issue is not resolved.

Patrick

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LM3697: Seeing 5V on the current sink