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Your LED Constant Current Source Scheme AND8109/D is very interesting for my backlighting applications, spesially the circuit in Figure 4. First I will use LM317T so give 1.5A. I will use only one 1W, 0.35A white Golden Dragon (LUW W5AM) LED in each leg. My question is: Can you set up the equation for resistor Rsense. How big are it? And can you also set up the equation for resistor Rbase for MPS2222. How big are it? How many legs can LM317T supply? I thank you for your attention. 1165 2014-01-14 12:09:42.195
I'm looking for a chip (SOT23-5) to drive 2 x 10 LEDs (10 LEDs in series, 2 strings in parallel) from lower or equal then 3.0V. So the LED current must be 40mA and the max. voltage about 35V. I could not find a suitable chip in your portfolio. Did I miss something or do you simply have no suitable chip ? Best regards Herbert Demmel 1417 2013-09-18 13:45:28.927
I am using the CAT4106. Earlier datasheets has the EN/PWM high time as 0.2us. Now I see that it is 100us. DOes this mean I can't drive the device with a 1000:1 ratio? 1320 2013-08-14 14:02:17.726
We have been using CAT4240TD-GT3 part for 24 V/40mA application for LCD backliting purpose. Below is out inductor value calculation for Output Voltage=19.2V and LED Fwd Current=40mA. Our input Voltage is 5V. D=(Vout - Vin)/Vout = (19.2-5)/19.2 = 0.739 (74% duty cycle). IL=I out/1-D = 40m/ (1- 0.739) = 0.153Amp. Ipk = IL(1+(ripple ratio /2)) = 0.153(1+(0.4/2)) = 0.1836Amp. L= (Von*D)/(ripple*IL*f) = (5*0.739)/(0.4*0.153*(10^6)) = 60.3758uH (f = 1MHz switching frequency). Final Inductor Value = 60uH. We wish to confirm above values suitable for Vout=19.2 with 40 mA. We also have input=5V, output Voltage=23.1V and Current=40mA for this part and used inductor value is 47uH where as calculated value is 53 uH. But system is working ok. Please advise. Regards Yk 1690 2013-04-17 08:56:54.349
Hello. my name is thomas ciciyan, from iran. my question is about LED drivers of an huge full color LED TV. how does that LED drivers work with 3 or more color LED's, and with a lot of different color depths depended on a video signal? can you show me a diagram to demonstrate combination of circuits or block diagrams that converts a video signal to a momentary constant current to drive 3 different color LED's? 1599 2013-04-04 09:48:07.418
Hi. I am writing to you to inquire about CAT4106. Here is an excerpt from the datasheet of the CAT4106 :"An integrated DC/DC boost converter is used to generate the high voltage output required to power the LED strings. Up to a maximum of 6 W of LED power can be delivered when powered from a 12 V supply." There is no information what maximum power can be delivered to LEDs when CAT4106 is powered with 5V. My question is: Can CAT4106 properly power 4 strings of 8 LEDs each (Vforward = 28.8V, If=35mA thus P=4.032W) when powered with 5V? 1550 2013-02-28 08:42:14.145
Hi, My earlier question was "We are using this device P/N: CAT4240TD-GT3 for one of LCD boost operation with 24V Vout. We need to understand how this device can used for 9.3V PWM out with 120 mA with Vin = 5V "..to add further..we are using PWM signal input to SHDN Pin to control PWM output for dimming appliction. VIN is at 5V. Are we able to get 9.3V @ 120 mA if we get the value of Rs = 2.5Ohm and L= 26 uH..please confirm.. 1626 2013-01-23 14:42:38.946
Hi, We are using P/N: CAT4240TD-GT3 for 24V (80mA) Vout for LCD backlight application. How can we use the same part for 9.3 Vout at 120 mA application. We are not able to get data on this. There is no info available in datasheet. Regards Yogesh 1688 2013-01-22 15:45:27.864
I need to drive 8 LED's from around 2.8 Vin and I have limited height available in the end application. Do you know where I can find something that might work? 2066 2011-05-30 18:39:06.0
Hi, our application needs to drive 2 different LED backlights (for 2 different LCDs). One of them has 2 LED strings and the other has 3 LED strings. Now my concerns are: 1. When we drive the LCD that has 2 strings, 2 other strings remain open and CAT4106 asserts the ;FAULT; signal indicating open LEDs on the un-used strings. I want to avoid this so that if an actual ;open LED; case occurs, the uC should know that. 2. When we drive the LCD that has 3 backlight strings, one remains open and the ;FAULT; signal gets asserted again indicating open LED string on un-used channel. I want to avoid this so that if an actual ;open LED; case occurs, the uC should know that.. Unfortunately, we need to implement this on the same platform without the BoM control (I mean the exactly same set of components should be able to handle both cases) One solution that I had in mind was to short LED3 ; LED 4 together to drive the 3rd string. However this doesn't solve the problem because in the case when the LCD with 2 strings in place, the ;FAULT; signal will be asserted again. Questions: 1. How can I design the circuit (supporting both LCDs with 2 ; 3 string LED confiigurations) without loosing the ;FAULT; feature in our application? 2. Is there any adverse impact of conecting a resistor of sufficient wattage in place of LED string. 2070 2011-05-27 01:12:32.0