Hello,
I'm designing a driver for a set of 3 Cree XPG2 LED's in series. I think my parameters are pushing the limit of the maximum switching current, but I'm not sure I am understanding exactly which current in the circuit is the switching current.
Specs:
Vin MIN = 3.45V
Vin MAX = 4.20V max
Vout = 9.0V
I LED = .860A (PWM will be used for dimming)
I Ripple = .198A (23%)
I in = 2.64A (assuming 85% efficiency, @Vin MIN = 3.45V)
I L MAX = 2.84A Question: is this not allowed to exceed 2.8A?
L = 27uH
C1 = 10uF Question: I simply selected value from the suggested range, is there a proper calculation for selection?
D MAX = 61.7% (@Vin MIN = 3.45V)
R ESR = 20mOhm (Cap spec sheet)
C2 = 24uF Question: Not sure if I calculated this one correctly. Is Delta Vout the range of output Voltage?
Any assistance or review of my layout is greatly appreciated.
Best,
Casey