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Author Topic: Difference between 74hc595 and 74hct595  (Read 951 times)
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I want to build a bigger LED matrix display ( 120*8 ). I used 74hc595 for a smaller one and it worked great, but I had to limit current to 75mA / 8 ~ 9mA. That means LEDs didn't have enough brightness.
So, this is the question: I saw that 74hct595 has 160mA current output. Is that true, or I'm reading datasheet wrong? If that is true I can use almost 20mA per pin which would be great! smiley
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That sounds wrong to me....

If you really insist in drawing power straight from the shift register instead of using transistors then you need one that's specifically designed for the job, eg. http://www.ti.com/lit/ds/symlink/tpic6b595.pdf
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I also recommend that same  IC and it's precisely why I have some in my parts drawers.

I doubt you get better per pin current with either HC or HCT.  HCT was intended to interface the CMOS parts with Legacy TTL (Meaning 5V logic 5V supply).   HCT would not imply higher current capacity per pin.

My Philips datasheet says MAX Package current (Vcc to GND) -is 70mA... so your number has to be wrong.  If each pin were driving a 10mA load, you will exceed *recommended* current for the 74HCT595 device.
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You want a high-current 595 replacement like this: https://www.sparkfun.com/products/734

The 74HCT family are like the 74HC but are restricted to 5V supply and have TTL-compatible input
levels (0.8V / 2.4V).
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I have a board with TPIC6B595s that will work great for that.
Build your matrix as common anodes for the 8 rows driven directly by the '328P, and common cathode for the 120 columns sunk by the TPIC6B595s.
Use two boards, daisy chain the control signals, with just shift registers & caps on the 2nd board.

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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
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$5/bare board, mailed to US locations.  
« Last Edit: February 11, 2013, 03:46:37 pm by CrossRoads » Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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That is a very good price. Problem is that I'm from Serbia and I can't order from you.  smiley-red
Even worse than that is, for some reason, I can't find TPIC6B595 anywhere in Serbia. So I'll have to go with 74hc595...
Regardless, thank you all for your time. smiley
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I can't find TPIC6B595 anywhere in Serbia.

eBay?

http://www.ebay.com/sch/i.html?_nkw=TPIC6B595

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You don't have paypal in Serbia?
USPS will send mail there, I'll see if we can get a price for a small padded envelope for a 10cm x 10cm card.
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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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