# Tantalum capacitor selection in LT3652 Buck Converter

In this circuit, a buck solar single cell Li-Ion battery charger, I need to select C3 and C4 tantalum capacitors. $V_{BAT(FLT)}$ is going to be 4.2 V, hence I selected:

$C3_{VMAX}=10\text{ V}$ $C4_{VMAX}=10\text{ V}$

Datasheet suggests low ESR tantalum capacitors but the supplier has capacitors ranging from $1\text{ }\Omega\text{ to }80\text{ }\text{m}\Omega$.

1. Are the $C3_{VMAX}$ and $C4_{VMAX}$ values I picked, correct for this application?
2. What ESR values should I pick for the tantalum capacitors for this application, and why?
• If you look at the datasheets for the suggested Sanyo OS-CON or POSCAP capacitors, you will find the ESR for those. – Andrew Morton Feb 4 '17 at 18:41
• @AndrewMorton I thought the exact series wasn't mandatory. Anyway I found a 47 uF 10V POSCAP at 35 mOhm. – Nic1337 Feb 4 '17 at 19:49
• You wanted to know the acceptable ESR, so I thought that looking at capacitors with acceptable ratings would be a good guide. – Andrew Morton Feb 4 '17 at 20:18
• It's the first time I work with tantalum capacitors, so I'm inexperienced. Do you think that the 35 mOhm cap I found should be fine? – Nic1337 Feb 4 '17 at 20:22