Help on ULN2803

[RonH]

I have an application the requires 150ma to be drawn from a ULN2803 pin, with my duty cycle I should be good for ~180ma but I don't really want to be that close to the edge if I don't have to be.
Does anyone know if it's acceptable to parallel 2 lines of the darlington drivers together?

Ron

 

[audioguru]

The max allowed current of one darlington in a uLN2803A is 500mA but the package might over-heat if two darlingtons or more each have 500mA.

 

[mneary]

You can put two in parallel, but if your load is only 180mA it wouldn't seem to be necessary.

It's strange that the data sheet lists 500mA "per device" and no total-package limit. I wouldn't hesitate to use it for 500mA x2 or even x4, but not all 8 at once.

 

[RonH]

My datasheet does state the max current for each channel at 50% duty cycle, this is how I calculated my current rating for 4 lines.

I was just wondering how they will share the load, will one hog the current more and not help me at all?

Ron

 

[ericgibbs]

hi,
I earlier posted a detailed breakdown of this ULN2803A post regarding current/dissipation.......................ITS NOW GONE.!!!!!!!!!!!!!!!!!!!!!

 

[Vizier87]

EM is gonna get his fingers on it...

 

[ericgibbs]

hi,
A quick summary of my missing post.

The Vdp at VCE sat @ 150mA is 1V, so thats 1.2A total for all 8 outputs, thats 1.2Watts

The rated dissipation is approx 1.2W when mounted on a pcb.

A rough guide would be a max 150mA/output for all 8 outputs at 150mA.

 

[RonH]

I adjusted my circuit and it works fine.

I have one last question, since this device is a sinking driver can I assume my loads can have different voltage levels i.e. 2@24V 1 @5V?

Ron

 

[ericgibbs]

I adjusted my circuit and it works fine.

I have one last question, since this device is a sinking driver can I assume my loads can have different voltage levels i.e. 2@24V 1 @5V?

Ron

hi Ron,
The loads can have different voltages, providing you leave the diodes common pin o/c

EDIT:
AS you are using 24V and 5V you could tie the diode common to +24V

 

[Boncuk]

hi,
A quick summary of my missing post.

The Vdp at VCE sat @ 150mA is 1V, so thats 1.2A total for all 8 outputs, thats 1.2Watts

The rated dissipation is approx 1.2W when mounted on a pcb.

A rough guide would be a max 150mA/output for all 8 outputs at 150mA.

Hi Eric,

can the outputs (ULN2003) of e.g. three parallel channels sink higher current (1.5A) if a heat sink is glued to the IC body or use 6 paralleled channels?

I'm using those outputs for an egg turner motor in an incubator controller. Three outputs are unused and one is used as an LED driver (10mA).

The motor will run for about one minute (maximum) within a selectable time interval of one to 24 hours in steps of one hour.

Kind regards

Hans

 

[ericgibbs]

hi Hans,
It does say in the datasheet that 'outputs can be paralleled for higher output currents'

The VCE sat at 500mA could be approx 1.7V, which is 0.85 Watt ,so for 1500mA that would be 2.55 Watts

One of my datasheets says 2Watt max.

My conclusion is that the ULN2003 would be over run at 1.5A @ 0.5A for 3 outputs.