LM2623: Capacitor questions

Hi Steven,

The input capacitor is required to reduce the input ripple and noise for proper operation of the regulator. The size can also be reduced if the input of the regulator is very close to the source output. The size will generally need to be larger for applications where the regulator is supplying nearly the maximum rated output or if large load steps are expected. A minimum value of 10µF should be used while a 22µF to 47µF capacitor may be required for higher power and dynamic loads. 

I think both capacitor can be used in input capacitor, I recommend following datasheet and EVM user guide design.

For output, it is recommended that low ESR (Equivalent Series Resistance, denoted RESR) capacitors be used such as ceramic, polymer electrolytic, or low ESR tantalum. A minimum value of 10µF is recommended and may be increased to a larger value for smaller ripple.

Best Regards，

Eric Yue

Hi Erick, would you recommend that a low esr tantalum capacitor be used for in the input capacitor? Also, do you recommend both input and output to be tantalum or can a ceramic capacitor work? Lastly, could you clarify the following remark you made in your last response "I think both capacitor can be used in input capacitor, I recommend following datasheet and EVM user guide design". Thank you so much!

1. Erick, sorry for the extra message. I forgot to ask one thing in addition to my last reply. I am wanting a 5v regulated output that is coming from 2 parallel lithium ion 18650 batteries. Would you recommend using thw 4.7pF capacitor as in the datasheet and what specs should it have ( should it have a low esr etc)?

Hi Steven,

I think both capacitor (low esr tantalum capacitor and ceramic capacitor) is okay for input and output capacitor. Because there is recommended design in datasheet and EVM, it is convenient to follow the design and also both capacitor is okay. Please make sure input and output capacitor is close to IC in layout.

I think 4.7pF is okay for one lithium battery input and 5V output. Ceramic capacitor is suitable for C3 because of spec and space.

Hi Eric, I am wanting to use a 220uF ceramic capacitor for the input capacitor as is called out on the LM2623 Evaluation board. Is there a downside to choosing a higher value ceramic capacitor than is needed for the LM2623?