5
\$\begingroup\$

I am designing a small device with two MAX485 chips.

enter image description here

Do they need the decoupling capacitors on the 5V power?

\$\endgroup\$
  • 4
    \$\begingroup\$ This really depends on the impedance and inductance of your supply to the chip; a decoupling capacitor is generally best practice, generally has low cost/complexity for assembly, and shouldn't hurt. \$\endgroup\$ – nanofarad Jan 29 '19 at 23:41
  • 10
    \$\begingroup\$ As a general rule ALL IC's should have ample decoupling capacitors. \$\endgroup\$ – Sparky256 Jan 29 '19 at 23:46
  • 3
    \$\begingroup\$ The bypass cap are almost universally used with the purpose of minimising the power supply impedance. \$\endgroup\$ – pantarhei Jan 29 '19 at 23:49
  • 3
    \$\begingroup\$ Sometimes you can share decoupling caps if you know the feed inductance (e.g. 10nH/cm * length * 2), current rise time and tolerance for LdI/dt=V drop \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jan 30 '19 at 1:58
  • \$\begingroup\$ Ask yourself, "What do I know that the manufacturer doesn't?" \$\endgroup\$ – Transistor May 3 at 11:38
13
\$\begingroup\$

Yes. All almost ICs need decoupling capacitors. Devices such as these '485 drivers especially need them due to the current surges the device experiences when switching the signal states due to the low value termination resistors used on the bus lines.

| improve this answer | |
\$\endgroup\$
  • 4
    \$\begingroup\$ You could debate whether all ICs strictly need decoupling caps, but it never hurts to add some. \$\endgroup\$ – Hearth Jan 30 '19 at 0:04
  • \$\begingroup\$ @Hearth this was my question. If it does not hurt \$\endgroup\$ – P__J__ Jan 30 '19 at 0:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.