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Meaning of Vce(sat)?

Started by Daniel Pitts March 9, 2014
I'm going to be using ULN2803APG in a design of mine, and I just noticed 
on the datasheet [1] that Vce(sat) typ is 1.3 at 350ma.

Does that mean that the voltage drop across the Vce will typically be 
1.3 at that current? Or does that mean the voltage for Vbe needs to be 
that high to have saturation?

[1] 
<http://www.semicon.toshiba.co.jp/info/docget.jsp?pid=ULN2803APG&lang=en&type=datasheet>
On 3/9/2014 3:21 PM, Daniel Pitts wrote:
> I'm going to be using ULN2803APG in a design of mine, and I just noticed > on the datasheet [1] that Vce(sat) typ is 1.3 at 350ma. > > Does that mean that the voltage drop across the Vce will typically be > 1.3 at that current?
'Fraid so. It's a Darlington, intended for high voltage outputs. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On 3/9/14 12:39 PM, Phil Hobbs wrote:
> On 3/9/2014 3:21 PM, Daniel Pitts wrote: >> I'm going to be using ULN2803APG in a design of mine, and I just noticed >> on the datasheet [1] that Vce(sat) typ is 1.3 at 350ma. >> >> Does that mean that the voltage drop across the Vce will typically be >> 1.3 at that current? > > 'Fraid so. It's a Darlington, intended for high voltage outputs.
That was what I was afraid of. I should still have enough headroom, but that is wasting a bit of power... Any suggestion on a replacement part? I need to enable/disable 8 lines with logic level inputs. It can even be a 1-of-8 decoder I just need it to support up to 1A, and I'd like it to be relatively cheap. My load is going to 24 parallel LEDs (3.3v Vf for 16 of them, 1.8 Vf for 8), each with a constant current sink in line with them. Cheap, for me, is < $1.25 for 8-in-8-out, or < $2.0 for 3-in-8-out (since I'd be able to replace two chips in that case). Thanks, Daniel.
On 09/03/14 20.21, Daniel Pitts wrote:
> I'm going to be using ULN2803APG in a design of mine, and I just noticed > on the datasheet [1] that Vce(sat) typ is 1.3 at 350ma. > > Does that mean that the voltage drop across the Vce will typically be > 1.3 at that current? Or does that mean the voltage for Vbe needs to be > that high to have saturation? > > [1] > <http://www.semicon.toshiba.co.jp/info/docget.jsp?pid=ULN2803APG&lang=en&type=datasheet> >
Hello Daniel How about using power MOSFETs?: e.g. DMN6040SSD: 60Vmax, 4.1Amax, 55mOhm max, cheap (normally twice as expensive) (two in each so-8), Logic Level Gate (means fully on while Vgs<5V) Cin=1,3nF: http://www.digikey.com/product-detail/en/DMN6040SSD-13/DMN6040SSD-13DICT-ND/3481122 DMN6040SSD: http://www.diodes.com/datasheets/DMN6040SSD.pdf /Glenn
On 3/9/14 1:25 PM, Daniel Pitts wrote:
> On 3/9/14 12:39 PM, Phil Hobbs wrote: >> On 3/9/2014 3:21 PM, Daniel Pitts wrote: >>> I'm going to be using ULN2803APG in a design of mine, and I just noticed >>> on the datasheet [1] that Vce(sat) typ is 1.3 at 350ma. >>> >>> Does that mean that the voltage drop across the Vce will typically be >>> 1.3 at that current? >> >> 'Fraid so. It's a Darlington, intended for high voltage outputs. > > That was what I was afraid of. I should still have enough headroom, but > that is wasting a bit of power... > > Any suggestion on a replacement part? I need to enable/disable 8 lines > with logic level inputs. > > It can even be a 1-of-8 decoder I just need it to support up to 1A, and > I'd like it to be relatively cheap. My load is going to 24 parallel > LEDs (3.3v Vf for 16 of them, 1.8 Vf for 8), each with a constant > current sink in line with them. > > Cheap, for me, is < $1.25 for 8-in-8-out, or < $2.0 for 3-in-8-out > (since I'd be able to replace two chips in that case).
I should add, I'm talking about price for quantities < 20 at the moment, not including shipping.
On 3/9/2014 4:33 PM, Daniel Pitts wrote:
> On 3/9/14 1:25 PM, Daniel Pitts wrote: >> On 3/9/14 12:39 PM, Phil Hobbs wrote: >>> On 3/9/2014 3:21 PM, Daniel Pitts wrote: >>>> I'm going to be using ULN2803APG in a design of mine, and I just >>>> noticed >>>> on the datasheet [1] that Vce(sat) typ is 1.3 at 350ma. >>>> >>>> Does that mean that the voltage drop across the Vce will typically be >>>> 1.3 at that current? >>> >>> 'Fraid so. It's a Darlington, intended for high voltage outputs. >> >> That was what I was afraid of. I should still have enough headroom, but >> that is wasting a bit of power... >> >> Any suggestion on a replacement part? I need to enable/disable 8 lines >> with logic level inputs. >> >> It can even be a 1-of-8 decoder I just need it to support up to 1A, and >> I'd like it to be relatively cheap. My load is going to 24 parallel >> LEDs (3.3v Vf for 16 of them, 1.8 Vf for 8), each with a constant >> current sink in line with them. >> >> Cheap, for me, is < $1.25 for 8-in-8-out, or < $2.0 for 3-in-8-out >> (since I'd be able to replace two chips in that case). > I should add, I'm talking about price for quantities < 20 at the moment, > not including shipping. >
You'd think that somebody would make a MOSFET version, but AFAIK they don't. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Den s=F8ndag den 9. marts 2014 21.43.46 UTC+1 skrev Phil Hobbs:
> On 3/9/2014 4:33 PM, Daniel Pitts wrote: >=20 > > On 3/9/14 1:25 PM, Daniel Pitts wrote: >=20 > >> On 3/9/14 12:39 PM, Phil Hobbs wrote: >=20 > >>> On 3/9/2014 3:21 PM, Daniel Pitts wrote: >=20 > >>>> I'm going to be using ULN2803APG in a design of mine, and I just >=20 > >>>> noticed >=20 > >>>> on the datasheet [1] that Vce(sat) typ is 1.3 at 350ma. >=20 > >>>> >=20 > >>>> Does that mean that the voltage drop across the Vce will typically b=
e
>=20 > >>>> 1.3 at that current? >=20 > >>> >=20 > >>> 'Fraid so. It's a Darlington, intended for high voltage outputs. >=20 > >> >=20 > >> That was what I was afraid of. I should still have enough headroom, bu=
t
>=20 > >> that is wasting a bit of power... >=20 > >> >=20 > >> Any suggestion on a replacement part? I need to enable/disable 8 lines >=20 > >> with logic level inputs. >=20 > >> >=20 > >> It can even be a 1-of-8 decoder I just need it to support up to 1A, an=
d
>=20 > >> I'd like it to be relatively cheap. My load is going to 24 parallel >=20 > >> LEDs (3.3v Vf for 16 of them, 1.8 Vf for 8), each with a constant >=20 > >> current sink in line with them. >=20 > >> >=20 > >> Cheap, for me, is < $1.25 for 8-in-8-out, or < $2.0 for 3-in-8-out >=20 > >> (since I'd be able to replace two chips in that case). >=20 > > I should add, I'm talking about price for quantities < 20 at the moment=
,
>=20 > > not including shipping. >=20 > > >=20 >=20 >=20 > You'd think that somebody would make a MOSFET version, but AFAIK they don=
't.
>=20 >=20 >=20 > Cheers >=20
TI makes something they call "power logic" but is mostly shift registers Though I'd think something like http://www.ti.com/product/tpic6273 could be= made to work=20 -Lasse
G 
> DMN6040SSD: > http://www.diodes.com/datasheets/DMN6040SSD.pdf > > /Glenn
That could be OK, but note the threshold voltage could be as high as 3V.
On 3/9/14 2:07 PM, miso wrote:
> G >> DMN6040SSD: >> http://www.diodes.com/datasheets/DMN6040SSD.pdf >> >> /Glenn > > That could be OK, but note the threshold voltage could be as high as 3V. >
That's fine for my case. I'm using an 74HCT238 @ 5V to run the thing.
On Sun, 09 Mar 2014 13:33:03 -0700, Daniel Pitts
<newsgroup.nospam@virtualinfinity.net> wrote:

>On 3/9/14 1:25 PM, Daniel Pitts wrote: >> On 3/9/14 12:39 PM, Phil Hobbs wrote: >>> On 3/9/2014 3:21 PM, Daniel Pitts wrote: >>>> I'm going to be using ULN2803APG in a design of mine, and I just noticed >>>> on the datasheet [1] that Vce(sat) typ is 1.3 at 350ma. >>>> >>>> Does that mean that the voltage drop across the Vce will typically be >>>> 1.3 at that current? >>> >>> 'Fraid so. It's a Darlington, intended for high voltage outputs. >> >> That was what I was afraid of. I should still have enough headroom, but >> that is wasting a bit of power... >> >> Any suggestion on a replacement part? I need to enable/disable 8 lines >> with logic level inputs. >> >> It can even be a 1-of-8 decoder I just need it to support up to 1A, and >> I'd like it to be relatively cheap. My load is going to 24 parallel >> LEDs (3.3v Vf for 16 of them, 1.8 Vf for 8), each with a constant >> current sink in line with them. >> >> Cheap, for me, is < $1.25 for 8-in-8-out, or < $2.0 for 3-in-8-out >> (since I'd be able to replace two chips in that case). >I should add, I'm talking about price for quantities < 20 at the moment, >not including shipping.
Somebody, I think TI, makes an LED driver with eight built-in current sinks and a serial interface. It was mentioned here not long ago. We like to use the TPIC6595 for driving relays and LEDs. Serial input and eight open-drain mosfets. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation