iPhone backlight circuit operation question

[caphair]

Re: iPhone backlight circuit operation question

Why would Apple use an extra inductor and diode?
One inductor is 1uH/3.6A and the other 15uH/0.72A, so a high power and low power mode.

Boost converters have high peak input currents, even if the load is small.
I would say there's no room in an iPhone for a big capacitor to absorb those spikes and they switch over to the bigger inductor to lower electrical noise.
During a call, you want a low noise on power for cell comms. Also for lowering EMI with dual-frequency or multi-phase between the two boost converter outputs. But I don't see the one inductor capable of anything but low brightness.

It also looks like they are turning off the LED boost converter during a GSM TX (packet) burst, to save available power. Long range GSM transmit power can take almost 2A.

Is it in theory working like a power factor correction? Or simply to compensate for high current demand when needed?