Input/output capacitor selection for LT3756

Hello,

tyttuut said:

1. What does "A" stand for in the input capacitance equation? LED current? (See image)

This means current ILED should be in Amperes.

tyttuut said:

2. Is it possible to use electrolytic capacitors for better capacitance/cost?

Usually, electrolytic capacitors and ceramic capacitors are used together. Electrolytic capacitors' capacitance does not vary much when there is an applied DC voltage but can only handle low currents and usually have high ESR. On the other hand, ceramic caps are used as they have low ESR and can handle much higher current, but capacitance vary when dc voltage is applied.

tyttuut said:

3. What should the output capacitance be? The datasheet is ambiguous on this.

This is because it is dependent if you are working as a boost or buck mode. Since you are going to operate on boost mode, the output capacitance is calculated the same as for a boost regulator.

Regards,

Jhun

Thanks for the info, and sorry for getting back to this so late. I understand the use of A as a unit, but I'm unclear on what it means in the last part of the equation where it's used alone.

Hello,

Are you referring to the uF/A*us ?

If so, it's just used to cancel the units to have a unit of uF for the equation.

Regards,

Jhun

Hello,

Are you referring to the uF/A*us ?

If so, it's just used to cancel the units to have a unit of uF for the equation.

Regards,

Jhun