TL3843: To replace competitor - UC3843B

chentsu chung

Part Number: TL3843
Other Parts Discussed in Thread: UC3843, UC2843

Hi Team,

Our customer use TL3843 to replace UC3843B, but found that the Eff. of TL3843 is lower than UC3843B.

1. RD test TL3843 by directly replacing without any hardware modification like X'mer, MOSFET, LAYOUT, etc., what parameter makes this difference?

2. This is an old project, so we can only adjust the value of Caps and resistors, how TI recommend us to do for better performance?

Eff. testing table:

Vds waveform: (white one is TI's TL3843, yellow one is UC3843B)

Thank you.

Best regards,

C.T.

over 6 years ago

0 Teng Feng over 6 years ago

TI__Genius 13660 points

HI chentsu,

TL3843 is pin-for-pin compatibility to UC3843 without circuit change.

I found that the efficiency of UC3843 is tested when input power is 18W while TL3843 is tested at 20W, this will cause different results. Please compare the efficiency at some input power.

Besides, the efficiency data is not calculated enough precise, please account the data to two decimal places.

Regards,

Teng

0 Teng Feng over 6 years ago in reply to Teng Feng

TI__Genius 13660 points

Hi chentsu, I haven’t heard back from you, I’m assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has locked due to time-out) – thanks, Teng

0 chentsu chung over 6 years ago in reply to Teng Feng

Mastermind 6180 points

Hi Teng,

Thanks you, but may I ask what makes the different Vds waveform? The peak voltage of Vds looks highier than competitor's.

Thank you.

0 Teng Feng over 6 years ago in reply to chentsu chung

TI__Genius 13660 points

Hi chentsu,

May I know which competitor is UC3843B from? so I can compare its deference to TI TL3843.

If you don't want share the information here, you can email me at teng_feng@ti.com

Thanks

0 chentsu chung over 6 years ago in reply to Teng Feng

Mastermind 6180 points

Hi Teng,

It's ST's 3843B, thanks for your great help.

Best regards,

C.T.

0 Teng Feng over 6 years ago in reply to chentsu chung

TI__Genius 13660 points

Hi Chentsu,

I haven't found obvious difference between UC3843B and TL3843, which can cause different Vds.

Are these two waveform tested under same Vout and output power? and which topology in this application? If a schematic can be provided, it will better.Thanks.

Teng

0 chentsu chung over 6 years ago in reply to Teng Feng

Mastermind 6180 points

Hi Teng,

Schematic: APP-10.7WL sch.pdf

The testing method is, just replace UC2843 to TL3843, and no load condition change.

When use TL3843, the load current will increase without any modifiaction.

Please help on this issue, thank youvery much!

C.T.

0 Teng Feng over 6 years ago in reply to chentsu chung

TI__Genius 13660 points

Hi chentsu,

TL3843 recommends a value of 5 kΩ or greater for RRT. could you adjust R54 and C15.

Besides, are you using an electric load or a resister load? I am confused that why output current will increase. Is that because output voltage increases?

Regards,

Teng

0 Teng Feng over 6 years ago in reply to Teng Feng

TI__Genius 13660 points

Hi chentsu, the thread will expire soon, I will close the thread for now, but if you have any further questions you can create a new thread. Thanks——Teng.

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TL3843: To replace competitor - UC3843B