TPS92661-Q1: TPS92661-Q1 Circiut Design

Hello Sora,

To answer your questions:

1. This device basically shunts across an LED to turn it off or opens the switch to turn the LED on. That causes fast changes in the total stack voltage. For that reason a buck-boost is a good solution to use with it. It requires some output capacitance which makes it too slow to respond to the transients. Furthermore when one LED is shunted all of the extra energy in the cap discharges through the LEDs/switches and it will have a very high peak current that can cause damage. When one switch opens all of the other LEDs will have a drop in current until the output cap charges. This device was really designed to work with a very high bandwidth hysteretic buck converter type device that requires no output capacitor. So with these specs this would be a two stage solution with a boost converter followed by something like an LM3409, TPS92515, or TPS92518.

2. In your case, yes. The switches are floating so they could be stacked as long as the max total string voltage is less than 60V. But you would be cutting it too close to the abs max so two lower voltage strings would be required. So you would need two buck converters.

3. Either way would work fine. But I would recommend A since you would only have to do one buck design (same output voltage) and then just use two of them.

Regards,

Clint