TLC59401: VLED dropped when OUTx set to low

Sara Jia

Part Number: TLC59401

Dears,

I hanve tested TLC59401 in my design. I met some problem when OUTX set from H to L ,and OUTX is L , VLED is also dropped low, I think there is some incorrect in my sch,So pls check it for me,

Thanks a lot.

over 6 years ago

0 ivan yakimenko over 6 years ago

Prodigy 80 points

hi think its short-circuit happened. what is VLED in your design? pls send full sch to review

0 ivan yakimenko over 6 years ago in reply to ivan yakimenko

Prodigy 80 points

set IREF to 10K before testing

0 user5097458 over 6 years ago in reply to ivan yakimenko

Prodigy 30 points

Hi，Ivan：

Thank you for your reply! I am the tester and who is facing the problem and the VLED schematic is shown below：

The problem is that when OUTx is ON, it will drop to nearly 0V at first,and then rise to a normal ON level(the normal ON level depands on the LED number in a strip and the VLED value).so at the OUTx-0V time,the VLED is dropped too.According to my test,the problem disappears when I decrease the OUTx current, but the max current I have set is no more than 40mA/OUTx ever and the datasheet shows that I can get 120mA MAX current per OUTx. So I am confused,is there something wrong ?

0 ivan yakimenko over 6 years ago in reply to user5097458

Prodigy 80 points

C15 should be 100.0 uF (tantalum LOW ESR) in parallel with 1.0 ceramic capacitor, trace current loop SW->D2->C15->GND should be as short as possible. Also C14 you can remove it for faster feedback

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TLC59401: VLED dropped when OUTx set to low