TPS92692-Q1: about the TPS92692 led OUTPUT current

qinlei

Intellectual 430 points

Part Number: TPS92692-Q1
Other Parts Discussed in Thread: TPS92692

hello, i have one question about the TPS92692 ,

When i use the TPS92692 buck boost cc MODE, I test the LED output current wave .

i did not use the PWM dimming.

LED output current wave as following:

the output current is not straight and fluctuates up and down , the max value is 480mA,the min value is 400mA， why is this happening ?

and i used the dither frequency, i found that if i do not use the dither frequency function, the output current will become a straight line, could you help explain this for me ?

over 1 year ago

0 Tuan Tran74 over 1 year ago

TI__Mastermind 18890 points

Hello,

The dithering as you mentioned is really the spread spectrum in which we modulated the frequency to lower EMI. This can lead you some amplitude variation as you mentioned. You can read about it in section 8.3.3 of the data sheet.

0 qinlei over 1 year ago in reply to Tuan Tran74

Intellectual 430 points

please refer to the above picture.this is normal?

and i have checked the datasheet 8.3.3 and i think Spread Spectrum Frequency Modulation is the effect on the switching frequency,why does it affect the V(CSP-CSN) ? i also tested the V(CSP-CSN) wave and found the V(CSP-CSN)fluctuates up and down, so the led output current follows the V(CSP-CSN).

could you help explain this for me ?

thank you

best regards

0 Tuan Tran74 over 1 year ago in reply to qinlei

TI__Mastermind 18890 points

Qinlei,

It modulates switching frequency with the lower spread spectrum frequency and therefore you will see the lower modulation frequency on the output current.

Thanks Tuan

0 qinlei over 1 year ago in reply to Tuan Tran74

Intellectual 430 points

hello, i think the LED current should be Continuoued,I don't understand why the current fluctuates up and down. I didn't use PWM dimming.please help explain

0 Tuan Tran74 over 1 year ago in reply to qinlei

TI__Mastermind 18890 points

Qinlei,

Again, it the modulation of the lower spread spectrum frequency that does not. Please read the data sheet on this section. It's not related to PWM dimming at all.

Thanks Tuan

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TPS92692-Q1: about the TPS92692 led OUTPUT current