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Author Topic: HT1632C(Led Driver) IO current  (Read 2178 times)
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The datasheet says it takes 18ma to drive the Control IO low (Data/Clk) which seams very high to me, but i did email the manufacturer and they say 18ma is correct

I want to drive around 40 HT1632C's and will have all 40 CLK IO's tied together.

Does this mean to drive this CLK IO i need (18ma * 40) = 720ma so nearly 1amp to drive some IO? or have i done my math wrong?



Iv seen 4 of these chips been driven by PIC's before and they can only drive 20ma per pin, so im guessing im missing some thing?

Any help would be much appreciated.
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It looks like you are right from the data sheet, this is a surprise but if that's what they say that is what you should do.

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Iv seen 4 of these chips been driven by PIC's before and they can only drive 20ma per pin,
I think you are mistaking the word can for should.
It looks like that PIC chip was overloaded.

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Does this mean to drive this CLK IO i need (18ma * 40) = 720ma so nearly 1amp to drive some IO? or have i done my math wrong?
That's what I get as well. Mind you with all those LEDs you are not going to notice another amp.

You should buffer each chip with a 74LS04 (6 in a package) so that you can drive them with an arduino.
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Im using a LPC2106 which can only drive 4ma on its IO (ouch)  so yeah will deffo be using some sort of buffer/line driver i guess

http://www.sureelectronics.net/goods.php?id=972
the above board can drive upto 8 of these chips yet its using a little PIC so hows that driving (18ma *  8 )=144   when the PIC IO can only drive 20ma???

i also remember driving 8 of these chips using arduino my self, i know the arduino is 40ma per IO and i had all 8 CLK's tied together. so how was that working lol??

« Last Edit: November 03, 2011, 01:12:16 pm by russdx » Logged

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It is working by killing your arduino. It is not that it can only supply 40mA it is that it should not be made to supply more than 40mA otherwise you damage it.
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oh, so sure-electronics are selling a board that will probably die if its got 20ma PIC pins driving upto 8 18ma IO's tied together

can you get buffers/line drivers that can supply 720ma??, or do i need to start looking at some fast transistors?

Thanks

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Russ,
Where exactly in the HT1632C datasheet do you see those currents? Is it for pins OSC and SYNC? If so, those are not used for driving the 3216 display. You only need to use the pins WR, CS and DATA (as input only, if you are using the existing library). I could not find any spec saying WR and CS take 20mA.
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Is it for pins OSC and SYNC? If
And DATA.

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can you get buffers/line drivers that can supply 720ma??,
No you don't want one big drive. You have a buffer for each two or three chips and feed the input of the buffers with a common signal.
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Ah yes it does not mention CS/WR but Data is 20ma smiley-sad

It just says CLK/WR are pulled high using a 27k resistor (at least i think that is what it is saying)


hmmm i sort of wanted just ONE Clk wire comin from my control line that would go to all the HT1632C boards not like 8 of them from different buffers hehe
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i sort of wanted just ONE Clk wire comin from my control line that would go to all the HT1632C boards
Tough.
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hmm, why cant i drive this one line using a transistor?

I guess another idea would be to add a mini buffer to each LED board and drive all the buffers off a common line
« Last Edit: November 04, 2011, 12:03:20 pm by russdx » Logged

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My project is to have 32 little LED boards, each board will have 2 HT1632C driver chips.

below is what had in mind for wiring it all up

By russdx at 2011-11-04

Each board also has +12v +5 and GND


I guess to drive the IO i could put a mini 4port Buffer on each LED board and then use 1 buffer on my control board.
The reason i want it layed out like this is, that i can have a quite nice little bus loom to wiring it all together that is not to complex smiley

to display information, i will first select one of the chip select lines. which will intern select 4 boards(8chips) and then write data to all 8 chips at once using my 8 data lines. i do this 8 times thats all 64 chips updated!! using only 12 IO lines!!! smiley
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think ill stick one of these little buffer chips on each LED board
http://docs-europe.electrocomponents.com/webdocs/0cb8/0900766b80cb8696.pdf

they take nothing to drive, so can easily tie 64 of these inputs together and control from 1 buffer on my driver board smiley
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DATA is input/output, similar to GPIOs on ATmega328, for example. The datasheet for ATmega328 says DC current per I/O pin is 40mA.
Does that mean that the GPIO pin takes 40mA when used as input? I highly doubt it.
Similarly, the DATA pin on HT1632C, when used as output, can typically source 20mA.
As I said, the library only uses DATA as input.
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I see, iv been reading this data sheet all wrong. your right those values are for when the DATA is set to output and its saying it can drive 18-25ma

Im just using the chips inputs so i dont care about that value im just after the Pull high resistor resistance on the input IO (WR/CS/DATA)

which is says is 27k. (or is it saying you add a pull high resistor of this resistance?)
so i guess my new question is

if you tie 64 * 27k resistors together how much current do you need to drive them low lol? at 5v smiley

Im guessing
27k * 1/64 = 421ohms total resistance
and at 5v it should take 11.1ma to drive this

does this sound correct?

Thanks
« Last Edit: November 05, 2011, 09:36:49 am by russdx » Logged

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I think you only need one pull up resistor for each of the inputs.
Think I2C: you pull up SDA and SCL with one resistor per line, regardless of the number of the devices you have connected.
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