Re: USB port blew -- why?

From: larrymoencurly (larrymoencurly_at_my-deja.com)
Date: 10/07/04 

Date: 7 Oct 2004 03:40:32 -0700

"JAD" <Kapasitor@coldmail.com> wrote in message news:<10m9p9p6k9k4sdf@corp.supernews.com>...

> "larrymoencurly" <larrymoencurly@my-deja.com> wrote in message
> news:755e968a.0410031718.36d14f87@posting.google.com...

>> One of the ports of my NEC-based USB 2.0 card quit working because
>> the National Semiconductor LM3526 power controller chip failed.
>> I'm pretty sure that I didn't zap it with static or try to plug
>> it in backwards. The data *** for the LM3526 says that it's
>> protected against voltage, current, and even temperature, so what
>> happened?
>>
>> National Semiconductor says that each USB port must have a 120uF or
>> larger tantalum capacitor between +5V and ground for protection
>> against transients that occur during hot-plugging, and NEC's
example
>> schematic for their uPD720100A USB 2.0 chip shows the LM3526 using
>> 150uF aluminum in parallel with 0.1uF ceramic. But my USB card has
>> only a 100uF aluminum capacitor and maybe a ceramic capacitor in
>> parallel for this. Could this be why the USB port got zapped?
>> Would it help to solder a tantalum in parallel as well? Will it
hurt?

> what main board? FIC ECS MSI?...usb blew cause the board blows.

My main boards are cheap, FIC and ECS, so any built-in USB for them
uses an SiS or VIA chip. My NEC USB is a PCI card. But why couldn't
any built-in USB blow out because of something off the main board? I
had a built-in RS-232 serial port blow because someone tried to hot
plug a parallel printer port (vaporized a couple of tiny capacitors
used by the RS-232-TTL converter chip), no other damage.