The Ixys 10M45s chip needs a resistor to set the current.
I have a formula . Resistor (ohms) = 3000 divided by current (in ma)
So, for 35ma 3000/35 = 86R
BUT
on the data sheet there is a graph for the resistor values, and as I read that 35ma would be about 70R
What would the experts select for 35ma ?
I selected 75R cos it was the nearest I had.
http://ixdev.ixys.com/DataSheet/98704.pdf
CCS chip setting resistors.
- pre65
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#1 CCS chip setting resistors.
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#2
Hmm, I wondered about that formula when you first posted it, The graph shows 70R, I would use a preset and a bench supply to see what actually worked.
If you plot the equation on the graph you will see the difference.
If you plot the equation on the graph you will see the difference.
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#3
Thanks Nick.
So, the formula (not of my making ) is inaccurate, but gets one in the right area.
So, the formula (not of my making ) is inaccurate, but gets one in the right area.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
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#5
When I tested the cascode 10M45S, the relationship was linear but not as per your suggested formula, (tested with a battery and 1k resistor as recommended by Nick).
Typical points I had were:
3.4mA 810R
5.0mA 520R
8.4mA 63R
Don't know whether this would rule out the cascode pairs for the current you are thinking about. Looks like if you extrapolated these points, with zero set resistance you would get less than 9mA!!!
Typical points I had were:
3.4mA 810R
5.0mA 520R
8.4mA 63R
Don't know whether this would rule out the cascode pairs for the current you are thinking about. Looks like if you extrapolated these points, with zero set resistance you would get less than 9mA!!!
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#6
Actually that reminds me, I think I found a discrepancy between the formula and the graph on the thing's actual data sheet!
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#7
I often find that with valves. To no insignificant difference.Mike H wrote:Actually that reminds me, I think I found a discrepancy between the formula and the graph on the thing's actual data sheet!
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#8
That was what the image I posted was. the red dots are the formula, the line is the spec sheet.Mike H wrote:Actually that reminds me, I think I found a discrepancy between the formula and the graph on the thing's actual data sheet!
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#9
Doesn't look too bad until you realise its a log-scaled graph...Nick wrote:That was what the image I posted was. the red dots are the formula, the line is the spec sheet.Mike H wrote:Actually that reminds me, I think I found a discrepancy between the formula and the graph on the thing's actual data sheet!
I'd always go with a multi-turn trimpot (say about 100R) - no two devices are the same and even using 1% resistors (unlikely) matching currents can be tricky...
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