TPS61199: FBP Pin Resistance

Michael Peters1

Part Number: TPS61199

Hi,

Are there any drawbacks or issues to expect if the resistance on this FBP pin is very large, for example a 6MEG ohm resistor?

over 4 years ago

0 Yuting Shao over 4 years ago

TI__Genius 13001 points

Hi Michael,

Then the LED short detection threshold would be very high, so device may suffer damage from LED short fault.

BR,

Robin

0 Michael Peters1 over 4 years ago in reply to Yuting Shao

Prodigy 40 points

Hi Yuting,

Thanks for your response. I'm using 1.2Mohm at ISET to achieve 2mA LED current. That would require 6Mohm FBP resistor for 6V threshold.

Vled_short =( 6M ohm/1.21M ohm) * 1.229 V

My concern is the 1uA of programming current on the FBP pin. How much error can that generate over temperature/tolerance?

6 V threshold / 6M ohm = 1uA

Thanks

0 Yuting Shao over 4 years ago in reply to Michael Peters1

TI__Genius 13001 points

Hi Michael,

We don't have the accurate accuracy data for 1uA situation.

So why not set higher output current with low duty cycle PWM to generate 2mA current?

BR,

Robin

0 Michael Peters1 over 4 years ago in reply to Yuting Shao

Prodigy 40 points

Yuting,

So I have two set points one at 30 mA and another at 2mA. Parallel resistors at the ISET pin and an N-Channel MOSFET to switch between the two. Same cnofiguration at the FBP pin.

At 3mA (advertised on the datasheet) the FBP resistor is still going to set current down in the uA range, is that correct?

0 Yuting Shao over 4 years ago in reply to Michael Peters1

TI__Genius 13001 points

Hi Michael,

Current accuracy is worse for lower output. So I suggest you apply for an EVM and have a bench test.

BR,

Robin

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TPS61199: FBP Pin Resistance