BQ24610 ... ISET1 noise sensitivity?

John Bendel

Other Parts Discussed in Thread: BQ24610

Hello

I am working with the BQ24610 in an initial prototype board. I am getting noise on the ISET1 pin, which appears to be beyond the standard switching noise, so I suspect there could be noise coupling through another pin. Outside of the standard culprits ... Vcc, SRP ... has anyone found a pin that is particularly sensitive / needs better bypassing?

Is there a more detailed block diagram of the device ?

Thank you,

John

over 14 years ago

0 Wang5577 over 14 years ago

TI__Guru 56650 points

Does the noise frequency is same as the switching noise? I don't think the noise comes from the bq24610 internal circuit. Would you send me the ISET1 waveform? Is the output current stable? Does the output current follow that noise?

0 John Bendel over 14 years ago in reply to Wang5577

Prodigy 30 points

Hello Wang,

I have attached the file. The Current is stable with respect to line regulation (5V to 7V), but it's just not accurate ~20%. The Switching noise I can understand (although it's not good) .. it is what is happening in between the noise that I don't.

Thank you,

John

7484.iset1_8V_TI.tif

0 Wang5577 over 14 years ago in reply to John Bendel

TI__Guru 56650 points

It could still be a switching noise. Please check the LODRV signal to see if it has transient in between HIDRV signal transience.

The bq24610 has a cycle-by-cycle UCP comparator to prevent the inductor current flowing back to input. So, if the inductor current is lower than the UCP threshold, the LODRV turns off the low side buck FET.

0 John Bendel over 14 years ago in reply to Wang5577

Prodigy 30 points

Can you please go into more detail on how turning the Low Side MOSFET off prevents current flowing back into the input.

Thank you

0 Wang5577 over 14 years ago in reply to John Bendel

TI__Guru 56650 points

Please take a look the figure 7 in the datasheet. And, page 18 and 19, the "Cycle-by-Cycle Charge Under Current Protection" and "Synchronous and Non-Synchronous Operation" section.

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BQ24610 ... ISET1 noise sensitivity?