TLC5916: Question about output current difference

Satoshi

Guru 19495 points

Part Number: TLC5916

On the testing TLC5916, output current is set 15mA by configuration, but test result was 10mA.

Please let me know about why output current was differ.

Test condition is below;

・VDD：5V, 100Ω load

・Control signal(by FPGA) is attached below,

　Configuration is 15mA: 0xA6 at special mode and OUT0~5 output: 0x3F at normal mode

・REXT is fixed 500Ω

・Measured OUT0~5 voltage were 1.018V(100Ω load, 10mA)

　OUT6~7 are 0V by correct setting

Best regards,

Satoshi

over 5 years ago

0 Kenneth Du over 5 years ago

TI__Genius 14295 points

Hi, Satoshi,

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

Due to Chinese new year holidays, response maybe delayed.

Thanks for your understanding.

Regards,
Kenneth

0 Satoshi over 5 years ago in reply to Kenneth Du

Guru 19495 points

Kenneth-san

Thank you for reply, I understood.
I looking forward any update after holidays.

Best regards,
Satoshi

0 Shawn Ding over 5 years ago

TI__Expert 3190 points

Hi Satoshi,
the sequence and the configuration that you attached is right.

What is the supply voltage for LED? could you test the voltage on the resistor to get the output current?

Thanks!
Regards,

Shawn.

0 Satoshi over 5 years ago in reply to Shawn Ding

Guru 19495 points

Shawn-san

Thank you for reply,
Supply voltage for LED is 5V, and voltage on the resistor is 1.018V.

By the way, R-EXT(15pin)～GND voltage is 0.99V

Please advice me if there any cause or require test spec.

Best regards,
Satoshi

0 Shawn Ding over 5 years ago in reply to Satoshi

TI__Expert 3190 points

Hi Satoshi,
It seems that the Vref is not right. it should be 51/128*1.26=0.5V.
could you test the real waveform of the CLK/LE/OE/SDI?

Regards,
Shawn.

0 Satoshi over 5 years ago in reply to Shawn Ding

Guru 19495 points

Shawn-san

I attached real waveform of the CLK/LE/OE/SDI below.

※ch1: CLK, ch2: LE, ch3:OE, ch4: SDI

If there any noticed point, please let me know.

Best regards,

Satoshi

0 Shawn Ding over 5 years ago in reply to Satoshi

TI__Expert 3190 points

Hi Satoshi，
Theoretically it should be right.
I would suggest to remove the last clock of the switch mode command, just send 4 clocks and then followed by 8 clocks for data.
Please have a try and let me know if it works.

Thanks,
Shawn.

0 Satoshi over 5 years ago in reply to Shawn Ding

Guru 19495 points

Shawn-san

About 4 clock, is below signal correct?

Results was not change this issue.

Additional information is below;

・R-EXT(15pin)～GND: 0.99V

・Iout: 10mA (100Ω_load)

・Port setting are OK (OUT0: ON, OUT6: OFF)

Best regards,

Satoshi

0 Shawn Ding over 5 years ago in reply to Satoshi

TI__Expert 3190 points

Hi Satoshi,
Yes, that is correct.
Let's move to the email, and would you mind to send the schematic?
my email: shawn-ding@ti.com
Regards,
Shawn.

0 Shawn Ding over 5 years ago in reply to Satoshi

TI__Expert 3190 points

Hi, Satoshi,
I repeated the solution from email to here for the other customer reference.
It is the data transmitting sequence problem, change from LSB->MSB to MSB->LSB, and the problem resolved.

Please help to click "resolved", thanks!

Regards,
Shawn

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TLC5916: Question about output current difference