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# TPS61150A: Maximum current for IFB pin

Part Number: TPS61150A

Hello experts,

I have question for maximum current for IFB pin.
I plan to keep turning on LED without PWM. I will use only one channel.
How much current can we pull for IFB pin?
Datasheet explanation is little bit complex, I'm not sure which section should I refer.
Thanks and best regards,
Ryo Akashi
• Hi Ryo,

The maximum current is about 34mA for each channel.

Regards

Sean

• Hello Sean,

In datasheet P12, "It is designed to provide maximum 35mA current regardless of the current capability of the boost converter."
From this description, I think 35mA is maximum current.
Which is correct maximum current?
Thanks and best regards,
Ryo Akashi
• Hi Ryo,

Please refer to the datasheet for 35mA for the maximum current.

Regards

Sean

• Hello Sean,

I understand maximum current is 35mA for IFB pin.
Let me confirm my understanding.
The current for LED is pulled from IOUT pin.
So, we need to keep the average of inductor current under 35mA.
Is it correct?
Thanks and best regards,
Ryo Akashi
• Hi Ryo,

No, for boost topology, when internal switch turns on, inductor install energy, and when it turns off, it not only output current to IFBx channels, but also charge the output capacitors. And since there are two channels for those devices, so the average current of the inductor depends on the detail application.

Regards

Sean

• Hello Sean,

I understand the average current if the inductor depends on the system because there are LEDs and output cap.
My customer want to turn on LED without PWM.
To set LED current as much as possible (less than 35mA), we should follow equation (5). Is it correct?
If so, could you share me example of equation (5). I'm not sure how do I utilize  KISET.
Thanks and best regards,
Ryo Akashi
• Hi Ryo,

You can find this on data sheet spec table, the KISET=920(typical).

Regards

Sean

• Hello Sean,

I'm sorry, I missed KISET value on datasheet.
Let me ask maximum current for LED again.
Maximum current depends on the design.
How do we set LED current as large as possible?
Is there any good reference?
Thanks and best regards,
Ryo Akashi
• Hi Ryo,

Yes, the maximum current is a system level question, here is an application note that can help you to estimate the maximum current based on the detail application specs.

http://www.ti.com/lit/an/slvaeg0/slvaeg0.pdf

Regards

Sean

• Hello Sean,

Thank you for your suggestion app note. I will check the detail.