Problem Interfacing TI´s TLC59116F to Infeneon´s ITS42008 array

Discussion in 'The Projects Forum' started by abel2b, Jun 22, 2014.

  1. abel2b

    Thread Starter New Member

    Aug 18, 2012
    2
    0
    Hello, I got my very first Arduino UNO and as a beginner project I want to build an animated epoxy LED sign.

    OK so to make it short, I managed to interface the Arduino to TI´s 16 channel TLC59116 (Constant current driver) and TLC59116f (Open Drain driver). I somewhat have the code running 10 animations and still have more to do...

    I want to use one channel per letter, which are about 12cm x 10cm x 2 cm each have about 10 - 20 LED´s inside maybe more , The TLC59116´s can drive Max 120mA per channel but had overheating problems over 60mA; So I thought of using Infeneon´s ITS42008-SB-D Mosfet array http://www.infineon.com/cms/en/prod...?productType=db3a30443a06def4013a2bc7ff1b28be since they where giving away free samples, have small footprints, various protections built in (ex. OVP, OCP, OLP,thermal ) and diagnostics capabilities and can handle loads of 700mA (all channels active)and also they can be configurable with CMOS or VS/2 inputs .

    The problem is the TLC59116´s are either constant current or open drain outputs and I understand I can´t drive Mosfets directly !

    TI´s support forums suggest using just a pull up resistor like so (Note: fets are PNP ??) :

    [​IMG]

    And this might be fine for a regular mosfet, but the ITS42008 does not respond! :mad: according to Infeneon I should treat it like a regular FET and
    Sooo! can anyone tell me how to calculate this pullup resistor for the ITS42008 or R1 and R2 on the image below???

    [​IMG]

    I will appreciate any help or suggestions in solving this problem!

    Thank You !
    Abel Martinez
     
  2. Fibonacci

    New Member

    May 23, 2014
    25
    5
    With reference to the circuit that feeds the Q1, the function of the resistors R1 and R2 is as follows: R1 is the resistor which allows the 59116 fet work, referred to as pull up resistor and is calculated according to the maximum output current of fet, IoL, Vcc and the voltage of the fet VoL, so R1 = (Vcc-VoL) /IoL whose values are, according to TI, IoL = 120 mA, VoL = 400 mV, and Vcc = 12 V, according to the circuit, so that the minimum value of R1 must be 96.7 Ω. Choose R1 = 100 Ω. Now, the function of R2, set with R1 is provide a voltage to the gate of Q1 high enough to have a fast switching, this value, usually is 10 < Vgs < 20. Taking the value of 10 V, you need to solve the following voltage divider: R2 * VDC /(R1+R2) = 10. Solving for R2 is the value of 500 Ω. Choose 510 Ω, a commercial value.
    Regarding notation pnp is exclusive of bipolar transistors. In fets refers to the electronic channel formed and is channel n channel p, which are different concepts.
     
    abel2b likes this.
  3. abel2b

    Thread Starter New Member

    Aug 18, 2012
    2
    0
    Dear fibonacci :

    Thank you, for your time and effort it is of great help to me, it seems clear now, but I a couple of question if you don´t mind.

    I take it in R1 = (Vcc-VoL) /IoL. Vol is TI´s max Vol ?

    Also, I have some questions with this, in 10 < Vgs < 20 :

    1. Vgs is Infineon´s ITS42008 Input turn-ON threshold voltage (VINONx) or TI´s TLC59116F ?
    2. How did you come about with the numbers 10 and 20 in this formula and what do they represent ?

    Regarding the annotation misprint, I have to say it was noticed after I submited the post and still looking for a way to edit it ;)

    On a personal note, I noticed your in Juarez, Great! I used to live there many years, still have many friends and family nearby ........
     
  4. Fibonacci

    New Member

    May 23, 2014
    25
    5
    The value of VoL is the maximum, as well as the IoL, since it is designed for the worst-case scenario. With respect to the range between 10 and 20 for the Vgs (the gate-source voltage) is a range that give manufacturers of MOSFETS, for example, International Rectifiers, which ensures a fully formed channel, and is above the threshold, that is when the fet starts to drive.
    Interesting that you have lived here in Juarez, Mexico. If anything I can help you I am at ITESM campus Juarez.
     
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