TPS61169: Using separate bias to allow lower input voltage operation?

K A

Part Number: TPS61169
Other Parts Discussed in Thread: TPS61060, TPS61158, , TPS92360, TPS61166, TPS61165

Hello,

See attached picture for a summary of what I am looking for. LED driver application (5x LEDs in parallel). I am looking to separate the LED driver bias and LX supply rails, to accommodate a supply rail (VSUP as drawn) that can droop considerably below the input voltage range of TI's LED drivers.

Here is the info in text form:

Vin (labeled VSUP in picture): 0.5V to 3.2V. The 0.5V would be absolute worst case.

Vbias: 3.3V

LED Vf: 6.4V maximum

LED forward current: 100mA maximum total @ 100% duty cycle

Method of dimming will be PWM, ideally >20kHz to avoid any audible cap issues.

Is the drawing attached possible with TI's DC/DC solutions? I can't seem to find a boost or LED driver solution that can handle such a low input voltage, while also supporting an output voltage > 6V using the standard supply rail topology. I am hoping to avoid chaining 2x DC/DC converters together due to the inefficiency hit.

7 months ago

0 Patrick Yao 7 months ago

TI__Mastermind 23710 points

Hi,

We have TPS61060 as the synchronous solution. BTW, do you only accept the synchronous boost topology?

Patrick

0 K A 7 months ago in reply to Patrick Yao

Prodigy 10 points

Hello Patrick,

Can you explain why you recommend TPS61060 specifically?

We are open to asynchronous topologies as well, but we prefer synchronous due to the efficiency benefits.

0 K A 7 months ago in reply to K A

Prodigy 10 points

For asynchronous topologies, would TPS61158 / TPS92360 / TPS61169 allow us to use this approach with the separate bias supply rail?

0 Patrick Yao 6 months ago in reply to K A

TI__Mastermind 23710 points

Hi,

Because TPS61060 is the synchronous solution and we have tested before that it can support separated power supply.

TPS61158 is also a good choice, it is synchronous as well.

Patrick

0 K A 6 months ago in reply to Patrick Yao

Prodigy 10 points

Hello Patrick,

We have gone through the analysis for TPS61060, TPS61158, TPS61166, TPS61165 - all of these options will not work due to limited output current at low Vin (0.7V).

There are two options that DO work, based on our calculations:

TPS61169 / TPS92360 (these are our preference due to cost)
TPS61165

Could you verify the following:

What is the difference between TPS61169 and TPS92360, they look identical?
Can TPS61169, TPS92360, TPS61165 operate with separated power supplies to support low Vin voltages?
Can you double check the calculations below?