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Help choosing capacitors for LT8330/48V output

Category: Hardware
Product Number: LT8330

Hello friends,

First time posting here. 

I would like to use the LT8330 device for a 5v -> 48V  (10mA max) supply.

The reference design in the datesheet looks to be perfect fit.

Although I noticed that the capacitor (C3: MURATA GRM32ER71H475k) recommended for C3 is now obsolete.

Is there another suggestion for this part?

Also, should all the capacitors be the same in this design?

Thanks for any help!

Parents
  • Hi,
    a step-up converter has input current of triangular shape. This ripple current is much smaller than the average input current, so capacitor value is of less importance. Any manufacturer with at least 10V rating (suggestion) and at least 4.7µF will be good.
    The value depends on how sensitive is your design to EMI.
    The output capacitor has to buffer all the output current and is charged with short pulses of 10x output current. The output capacitor in the example circuit is the minimum value. If you have enough board space, I would reccomend as output capacitor 2x...4x CAP CER 4.7UF 100V X7R 1210. Be aware that real capacitance at 48V will be somewhat halved the face value.
    So, any manufacturer and any voltage rating above your 48V will be OK. If you want less ripple, you need more capacitance.
    Also the inductance value given is the minimum value. If you choose more inductance you get less ripple current at the input.

Reply
  • Hi,
    a step-up converter has input current of triangular shape. This ripple current is much smaller than the average input current, so capacitor value is of less importance. Any manufacturer with at least 10V rating (suggestion) and at least 4.7µF will be good.
    The value depends on how sensitive is your design to EMI.
    The output capacitor has to buffer all the output current and is charged with short pulses of 10x output current. The output capacitor in the example circuit is the minimum value. If you have enough board space, I would reccomend as output capacitor 2x...4x CAP CER 4.7UF 100V X7R 1210. Be aware that real capacitance at 48V will be somewhat halved the face value.
    So, any manufacturer and any voltage rating above your 48V will be OK. If you want less ripple, you need more capacitance.
    Also the inductance value given is the minimum value. If you choose more inductance you get less ripple current at the input.

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