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NCP3063 PWM controller not allow Emitter Followed configuration

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treez

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Hi,
The NCP3063 and the MC34063 PWM controller are virtually identical, except that the MC34063 offers the capability to drive the internal transistor(s) either with Darlington configuration, or with Emitter Follower configuration. NCP3063 only allows it to be driven in the Darlington configuration.

So why on page 5 of the NCP3063 datasheet does figure 7 refer to the “Emitter Follower” configuration. (this would surely only be for when an external power transistor was used in the case of NCP3063?)
Page 14 of AN920 shows the MC34063 being driven with emitter followed configuration, instead of the Darlington configuration.........

AN920
https://www.onsemi.com/pub/Collateral/AN920-D.PDF

MC34063 Datasheet
https://www.onsemi.com/pub/Collateral/MC34063A-D.PDF


NCP3063 Datasheet
https://www.onsemi.com/pub/Collateral/NCP3063-D.PDF
 

Hi treez,

Have you figured it out yet? :) I think you have mixed up which datasheet you were referring to. From the links in post #1, I see a schematic on page 5 of the MC34063 datasheet and graphs on page 5 of the NCP3063 datasheet.
 
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Thankyou d123, yes it is page 5 in both cases....and then page 14 in the AN920 app note.
 
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Hi,

Oh, now I see what you mean - not a schematic but the graph.

Looking at the simplified schematics, and I wouldn't trust this answer without experimenting or simulating it first, they look about the same to me r.e. how they can be used - so I guess I don't understand how those circuits/Darlington connection options work (separate or joined collectors).

I'd contact the manufacturer and ask, if you have the time to wait for an answer (and remember, "points mean prizes" - actually having product run numbers to add to the query/contact form field should theoretically bump a person up the speed-of-reply queue! Unless all queries are treated equally.)

I'm voting my answer down for low quality before you do.
 
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Thanks anyway.

We have another query about the NCP3063B.....

We would like to be able to shut down the NCP3063B...or at least, put it into a mode whereby it draws less bias current. –Less than the 4mA or so that the datasheet says the NCP3063B draws.
The NCP3063B has no “official” shutdown pin.
As such , we were thinking of adding a 1uF capacitor to the Timing pin and putting a small NFET in series with it. Switching this relatively large capacitor in would mean a vastly reduced switching frequency, and hence less bias current draw of the NCP3063B...would you agree?
 

The configuration referred to as "emitter follower" is also a darlington configuration and has both collectors connected to input voltage, see figure 5 in 34063 datasheet. In so far I don't understand the question.
 
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Thanks, i think they are referring to driving an external transistor...that's where the emitter follower is coming into it.
I wonder if i coulD start a new thread concerning shuttting down the NCP3063B?
 

Hi,

I don't personally know how effective your shutdown suggestion is nor can I guess what side-effects it may add but it sounds a reasonable postulation. Given that all the schematics numbered figure 16, 19, 22, 25, 27, 29 and 31 all show only one supply for the Vcc pin and the SWC pin, would it be an option to use a PMOS or PNP to shutdown the whole IC at the supply junction of Vcc and SWC (or would that be problematic for some circuit-related reason, as I assume you may have already considered that option)?
 
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