Spice Model for High Brightness LED
Microsemi model.
.model UPWLEDxx D(Is=1E-30 N=1.923 Rs=32.09 Eg=3.6 Cjo=63.87p
+ M=.1513 Vj=2.02 Fc=.5 Isr=1.304m Nr=3.4Meg Bv=12 Ibv=369.5u
+ Tt=432.8n Xti=5)
Symbol Name Parameter Units Default
IS IS Saturation current (diode equation) A 1E-14
RS RS Parsitic resistance (series resistance) Ω 0
n N Emission coefficient, 1 to 2 - 1
τD TT Transit time s 0
CD(0) CJO Zero-bias junction capacitance F 0
φ0 VJ Junction potential V 1
m M Junction grading coefficient - 0.5
- - 0.33 for linearly graded junction - -
- - 0.5 for abrupt junction - -
Eg EG Activation energy: eV 1.11
- - Si: 1.11 - -
- - Ge: 0.67 - -
- - Schottky: 0.69 - -
pi XTI IS temperature exponent - 3.0
- - pn junction: 3.0 - -
- - Schottky: 2.0 - -
kf KF Flicker noise coefficient - 0
af AF Flicker noise exponent - 1
FC FC Forward bias depletion capacitance coefficient - 0.5
BV BV Reverse breakdown voltage V ∞
IBV IBV Reverse breakdown current A 1E-3
Isr with NR controls the reverse biased leakage.
• IS controls forward and reverse current against voltage.
• N controls forward current against voltage.
• RS controls forward voltage at high current.
• CJO, M and VJ control variation of capacitance with voltage.
• BV and IBV control reverse breakdown characteristics.
• TT controls switching reverse recovery characteristics.
• ISR and NR control reverse biased leakage.
• EG controls barrier height.
• FC forward bias depletion capacitance coefficient.
http://www.cutestudio.net/data/products/spice/doc/simulation/simulators/sumos/non_linear/diode/index.php
Thursday, May 13, 2010
Tuesday, May 11, 2010
Mounting Cree XR-C on SchmartBoard
The Cree XR-C lamp is an SMT device with 0.7 pitch. Essentially it is a 12 line device, but lines 2 and 11 are empty (no connection), and lines 3-10 are fused.
But... This device can be mounted on SchmartBoard 202-0005-01
SOP, 4 - 72 Pins 0.8mm Pitch, 2" X 2" Grid EZ Version
http://www.schmartboard.com/index.asp?page=products_so&id=56
The 12 bands of the .7 pitch chip map nicely to 11 bands of the .8 pitch board. By removing bands 2 and 10 of the board, there is no bridging across the chip. It may not even be necessary to remove the two unused strips -- they may not bridge.
Soldering of the pad should work with the EZ method of the SchmartBoard. Nice trick.
Cree Lamp XR-C
The Cree XR-C lamp looks to be the best available lamp for the purpose.
350ma rated current.
Solderable package.
Neutral White has a very nice UV peak that may be useful. 80 lumen device. Two lamps might just be enough. 3 certainly would be.
http://www.cree.com/products/pdf/XLampXR-C.pdf
The neutral white XR-C part in the Digikey catalog is...
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=XRCWHT-L1-R250-006E5CT-ND
Digikey part number is XRCWHT-L1-R250-006E5CT-ND. Price is $7.65 per lamp.
350ma rated current.
Solderable package.
Neutral White has a very nice UV peak that may be useful. 80 lumen device. Two lamps might just be enough. 3 certainly would be.
http://www.cree.com/products/pdf/XLampXR-C.pdf
The neutral white XR-C part in the Digikey catalog is...
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=XRCWHT-L1-R250-006E5CT-ND
Digikey part number is XRCWHT-L1-R250-006E5CT-ND. Price is $7.65 per lamp.
LT 3080/3092 LDO
The Linear LT3080 is a 1 amp plus LDO adaptable to a constant current source.
The LT 3092 is a version of it set up as a current source for devices like LEDs.
http://cds.linear.com/docs/Datasheet/3080fa.pdf
It requires only one capacitor and two or three resistors for the circuit.
The circuit may be limited to 200 ma in the application of it as a power current source. That's a little low. But there are ways of getting it to play at a higher current. The simplest way is to use a shunt that provides another 200 ma or so around it. The regulator can adjust total current, while it doesn't need to source or sink the total current.
For real simplicity, and with a regulated 15 volt supply available...
Putting a resistor in series with the lamps makes good sense. A 5 watt resistor will work well. A 50 ohm resistor would pass under 300 ma. Raw empiricism may be needed to select the correct resistor value.
The LT 3092 is a version of it set up as a current source for devices like LEDs.
http://cds.linear.com/docs/Datasheet/3080fa.pdf
It requires only one capacitor and two or three resistors for the circuit.
The circuit may be limited to 200 ma in the application of it as a power current source. That's a little low. But there are ways of getting it to play at a higher current. The simplest way is to use a shunt that provides another 200 ma or so around it. The regulator can adjust total current, while it doesn't need to source or sink the total current.
For real simplicity, and with a regulated 15 volt supply available...
Putting a resistor in series with the lamps makes good sense. A 5 watt resistor will work well. A 50 ohm resistor would pass under 300 ma. Raw empiricism may be needed to select the correct resistor value.
SchmartBoard Development Board
The SchmartBoard 202-0011-01 is a potential development board to use for the circuit.
http://www.schmartboard.com/index.asp?page=products_qfp&id=70
It has the right pin configuration for the LT3029 in the MSE form factor.
But it does not have a thermal pad connection for the heat sink on the bottom of the LT3029.
One way of dealing with that would be to drill out vias under the sink, add foil under the chip, use wire or other material in the vias to conduct heat, and connect to the large ground plane on the back side of the SchmartBoard.
I got samples of LT3029 from Linear.
http://www.schmartboard.com/index.asp?page=products_qfp&id=70
It has the right pin configuration for the LT3029 in the MSE form factor.
But it does not have a thermal pad connection for the heat sink on the bottom of the LT3029.
One way of dealing with that would be to drill out vias under the sink, add foil under the chip, use wire or other material in the vias to conduct heat, and connect to the large ground plane on the back side of the SchmartBoard.
I got samples of LT3029 from Linear.
Ideas for Bung Cam Light Source
Background:
Wine makers need a way to inspect the inside of wine barrels. Bung Cam is a combination of a USB style camera, such as the Microsoft View Cam, and an illumination source.
Basics of illumination source are a 4 or 6 high brightness LED system -- possibly two colors (white and infrared, UV or some other narrow band light).
Issue is the design of the electronics for the LED supply. Using a 15 volt, 1 amp (15-25 watt) supply it would be possible to drive two strings of lights off of a dual linear regulator, such as the Linear LT3029 part.
Additional notes talk about details of the electrical circuits and construction.
Wine makers need a way to inspect the inside of wine barrels. Bung Cam is a combination of a USB style camera, such as the Microsoft View Cam, and an illumination source.
Basics of illumination source are a 4 or 6 high brightness LED system -- possibly two colors (white and infrared, UV or some other narrow band light).
Issue is the design of the electronics for the LED supply. Using a 15 volt, 1 amp (15-25 watt) supply it would be possible to drive two strings of lights off of a dual linear regulator, such as the Linear LT3029 part.
Additional notes talk about details of the electrical circuits and construction.
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