UCC28950: synch pin IO Characteristics

Alex Rovnan

Part Number: UCC28950

Can you give additional information regarding Iin high and Iin Low of the synch pin when used in slave mode? I am synchronizing several slaved converters to a master clock, but the typical logic i/o characteristics are absent from the datasheet with regard to the synch pin.

App Note SLUA609 gives some VERY basic information to state the Vih>2.8V and Vol<0.5V for proper operation. However, in order to know if I can meet those characteristics over temperature, I'll need to know the high and low input currents drawn by the synch pin. I would like to drive the synch pin with the output of a gate drive type optocoupler (HCPL0211), but the output of that device can sag as low as 2.4Voh under a few mA load.

It is very clear that UCC28950 loads the synch pin differently depending on it's enabled / disabled state. When disabled, UCC28950 loads the synch pin such that the logic out of TTL devices sag substantially as compared to the enabled state. None of this is described in the datasheet.

Regards,

Alex

over 7 years ago

0 Ulrich Goerke over 7 years ago

TI__Mastermind 31130 points

Hello Alex,

I have alerted the appropriate applications team to your issue and you should be hearing from someone soon.

Regards,
Ulrich

0 Brian Johnson96 over 7 years ago

TI__Expert 3200 points

Hi Alex,

I will work with our internal Teams on your "high and low input currents drawn by the synch pin" but this will take several working days before I can respond back.

0 Alex Rovnan over 7 years ago in reply to Brian Johnson96

Prodigy 140 points

Thanks Brian,
I have another question posted, with some detailed oscillograms attached, entitled 'UCC28950 dead time glitch', and have received no response. The post was put up by our FAE Jeff Coletti

We are developing several products built around UCC28950, and both products exhibit the same timing glitch. The layouts for the 2 boards are substantially different, and yet the symptom is nearly identical. If we can't get to the bottom of the dead time glitch. We will be forced to abandon this controller. I am happy to provide gerber files ,schematics, etc, but we need a response from the design team. This isn't our first rodeo, and we've exhausted all of the common solutions with regard to layout noise, ground bounce, synchronization etc that we are used to teasing out.