Why Synchronous Bucks are so limited? - Page 1
Forum section: electronics / general

author: makebit
author_rank: Unknown
timestamp: October 05, 2025, 02:02:08 pm
content: Hi,Massive numbers of equipments these days have a single 3.2-4.3V LIPO cellas their input power source.So why are there virtually no synchronous buck converters on the market with an inputvoltage range from 2V to 10V, and output range from 3V to 10V? (approx 1-2A current rating.)There are thousands upon thousands of synch bucks on the market but virtually none of this spec.As is known , one cannot use a synch Buck with an abs max voltage of say 7V with a LIPO, since ifits quickly connected, then the Vin may ring up to 8.4V.There are literally thousands of synch bucks with a vin abs max of 6V....absolutely useless when your powersource is a LIPO.

author: ejeffrey
author_rank: Super Contributor
timestamp: October 05, 2025, 03:05:13 pm
content: I think you will find that most of those millions of devices use converters with a Vin max of 6 V. Also keep in mind that most devices need a battery charger / power switch before the main DC DC converter. Those also typically have a 6V limit including for a 5v USB input.Ring up during hot connection is a real issue but managed by other means. First off, in most cases the battery is permanently connected or connected with very short leads. This is more of an issue when connecting the charger than the battery.Overshoot can be handled by limiting the inrush current, adding damping, or using overvoltage protection, which might be needed for ESD protection as well.USB has limits on the bus capacitance to limit inrush. Between that and the typically high wiring resistance this limits overshoot. Type C actually requires power switches to disconnect the bus power until it detects plug insertion.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 05, 2025, 03:26:00 pm
content: It's the certain IC process which produces devices with absolute maximum ratings around 6-7V for low cost. That suffices for 4.2V li-ion with margin to share. Hot-plug transients are easy to handle in proper ways. My favorite is damping with an electrolytic capacitor (and avoiding excess amount of MLCC)

author: mzzj
author_rank: Super Contributor
timestamp: October 08, 2025, 07:12:02 am
content: Is it just me or is our old friend treez/farindon/xyz back online?

author: Siwastaja
author_rank: Super Contributor
timestamp: October 08, 2025, 07:19:49 am
content: Quote from: mzzj on October 08, 2025, 07:12:02 amNow that you say it, clearly yes. Would you agree?He forgot to thank us all.

author: langwadt
author_rank: Super Contributor
timestamp: October 08, 2025, 08:03:33 am
content: how do you intend to get 3V output from 2V input with a buck ?

author: MF-jockey
author_rank: Regular Contributor
timestamp: October 08, 2025, 11:13:56 am
content: Please search for step-up modules. An example is theSX1308 Step Up Module.

author: JPortici
author_rank: Super Contributor
timestamp: October 08, 2025, 12:16:36 pm
content: Quote from: Siwastaja on October 08, 2025, 07:19:49 amdid you miss me mentioning that already?

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 15, 2025, 01:47:35 pm
content: What the OP seems to be looking for is obviously buck-boost converters, and I'm not even sure what the synchronous side of things has to do with it, unless it's a "hidden" requirement that they didn't fully disclose.

author: Gyro
author_rank: Super Contributor
timestamp: October 15, 2025, 04:35:57 pm
content: Quote from: SiliconWizard on October 15, 2025, 01:47:35 pmSee the OP's footer text.