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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?
  • 1
    \$\begingroup\$ If you look at the datasheets for the suggested Sanyo OS-CON or POSCAP capacitors, you will find the ESR for those. \$\endgroup\$ – Andrew Morton Feb 4 '17 at 18:41
  • \$\begingroup\$ @AndrewMorton I thought the exact series wasn't mandatory. Anyway I found a 47 uF 10V POSCAP at 35 mOhm. \$\endgroup\$ – Nic1337 Feb 4 '17 at 19:49
  • \$\begingroup\$ You wanted to know the acceptable ESR, so I thought that looking at capacitors with acceptable ratings would be a good guide. \$\endgroup\$ – Andrew Morton Feb 4 '17 at 20:18
  • \$\begingroup\$ 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? \$\endgroup\$ – Nic1337 Feb 4 '17 at 20:22

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