UDN2981 vs TLC59213

Discussion in 'General Electronics Chat' started by kgstewar, Mar 14, 2014.

  1. kgstewar

    Thread Starter Member

    Apr 5, 2012
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    For a circuit I am copying, they use a UDN2981. I find myself in possession of a few TLC59213 chips which seem to be similar except that the TLC59213 has a CLK and CLR pin. From the datasheet I understand to just hold the CLR high, but it's the CLK pin that has me confused. I just want the output to go high when the input goes high, and it appears this happens when the CLK is rising, but I'm not sure how I attach a CLK to this chip. Do I just make sure that when the input goes high, the CLK gets the same signal? Maybe tie all the inputs to the clock with diodes so that when one pin goes high it doesn't set all the other pins high? But then how does one keep the CLK rising? After the initial rise, it's just high...I am so confused...

    Many thanks!

    Kevin
     
  2. kgstewar

    Thread Starter Member

    Apr 5, 2012
    151
    6
    Any ideas or perhaps just use a UDN2981?
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,548
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    One is a simple driver the other is a latch, a different animal, also the ULN2803 is a popular one, inverter version allows High side switching .
    Max.
     
  4. panic mode

    Senior Member

    Oct 10, 2011
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    your understanding of operation of CLK and CLR is correct. if you don't want those pins look at ULN2803. UDN2981 is similar but the polarity is inverted (high side switch) and as a less popular option it costs more.

    having CLK allows to easily expand number of I/O. for example you can have two TLC59213 driven by same MCU port (8 bit) and only CLK is separate. then when MCU pulses CLK on one TLC59213, output of that chip will take a "snapshot copy" of MCU port (and keep the values until next time CLK is pulsed). then MCU may change value at the output port, and pulse CLK of the second TLC59213... this can be done very fast so it would look as those 16 outputs are changed simultaneously or controlled in real time. in reality we only used 10 outputs (8-bit data, and two CLK)
     
  5. kgstewar

    Thread Starter Member

    Apr 5, 2012
    151
    6
    Thanks for the responses! So if I were to swap out the UDN2981 in this circuit with a TLC59213, just tie the CLK pin on the TLC59213 to the CLK pin on the (unlabeled) MAX7219 in this circuit (which in turn is tied to the CLK pin on a uC)? The UDN2981 would be easier, but I have a bunch of the TLC59213s and was hoping to use them instead of having to order UDN2981s. Thanks again!
     
  6. panic mode

    Senior Member

    Oct 10, 2011
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    no no noooo

    THAT circuit is using multiplexing!

    this means that one of chips is source (UDN) and other is sink (ULN2803), and in-between you got 64 LEDs wired into a matrix.

    if you want to replace that with TLC59213 (to drive 64 LEDs), you would use different scheme that would take 8 TLC59213 and some program changes in the mcu
     
  7. kgstewar

    Thread Starter Member

    Apr 5, 2012
    151
    6
    I'm not sure I understand. I AM using multiplexing, using the exact same circuit, but instead of the UDN2981, I want to use a TLC59213, which is also a source driver. All that I am trying to do is figure out what to do with the extra two pins (CLR and CLK) that the TLC59213 has that the UDN2981 does not. If there is no simple way to substitute the TLC59213 for a UDN2981, that's fine, but it seemed to me that they were similar enough (although certainly not identical) that a substitution might be possible. Thanks!
     
    Last edited: Mar 15, 2014
  8. panic mode

    Senior Member

    Oct 10, 2011
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    oh, my bad... :eek:

    i missed that...;)
    sorry, i had 10 windows open and i typed the answer while looking at wrong datasheet (8ch. sink). looks like you are ok, in fact figure4 of datasheet shows the same thing:
    http://www.ti.com/lit/ds/symlink/tlc59213.pdf
     
  9. kgstewar

    Thread Starter Member

    Apr 5, 2012
    151
    6
    No worries! So I guess that gets me back to this question: Should I just join all the clock pins (uC, MAX7219, and TLC59213) to permit a TLC59213 to work in the circuit I had linked? Thanks!
     
    Last edited: Mar 16, 2014
  10. panic mode

    Senior Member

    Oct 10, 2011
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    i cannot tell that...
    yes you should be able to do so but... your clock need to be either synchronized with the display updates or - much faster (to appear as not clocked buffer stage).
     
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