Tlp525g-2

kwoodard

kwoodard

New member
Background - I'm considering making a version of my Arduino Light Controller with on-board SSRs for low-current applications. For instance, my mega tree this year is 32 channels of incandescent strings. Each channel is only 0.34Amps. Next year, I would like to simplify the setup and remove the separate AC SSRs and the CAT5 cabling that connects it all together (this cabling has been a reliability issue for me this year).

I'm also considering making some leaping light arches in the future -- each arch would be 8 channels of either 3 or 4 colors -- this would be perfect for a 32 channel controller with on-board SSRs.

Since I'm only designing this for low current applications, I first considered the VO2223A that is used in the DirkcheapSSRs. Since I like to keep my PCBs as small as possible to keep costs down, I began looking for chips that have multiple channels in the same chip that might use less board space than the VO2223A. I ran across the TLP525G-2 which contains two independent, isolated channels in a 8-pin DIP package. With this chip, I could get twice the board density compared to the VO2223A (1 channel per 8-pin DIP).

So, my question, has anyone used the TLP525G-2 in an AC SSR application or is there technical reasons why this chip would not be a good fit for this application?

Thanks,

Keith
 
Assuming that your driving circuits are capable of providing 10mA per channel, the part looks fine to me at first glance after taking a look at the datasheet.
 
Not directly. From a TLC5940, I'll sink the 10 ma. I'll have to double check the data sheet, but from memory, I think it will work.
 
kwoodard said:
Not directly. From a TLC5940, I'll sink the 10 ma. I'll have to double check the data sheet, but from memory, I think it will work.
Click to expand...

The datasheet indicates that the total Io = 130mA, which I interpret to be about 8mA per channel with all channels sinking max current.
If you decide to have a state where all channels stay on would you not exceed the rating for the TLC5940 with your 160mA?
Also, I don't know what the chips temperature rise will become using a full output of 160mA, or even 130mA.
 
LightUp,

I believe the Io = 130mA specifies how much current the chip can output, not sink. Looking at page 14 of the datasheet, it appears that you can control the max current sink of each channel through the sizing of the Iref resistor. It looks like it can sink up to a max of 120 mA per channel (for Vcc > 3.6V). But, I still need to run the power dissipation numbers at various temperatures, but at first glance, I think 10mA per channel should be okay. Of course, I may be misinterpreting the datasheet.

Keith
 
kwoodard said:
LightUp,

I believe the Io = 130mA specifies how much current the chip can output, not sink. Looking at page 14 of the datasheet,...Keith
Click to expand...

I guess I should use the power dissipation formula on page 15 of the datasheet and see what I get using the 120mA sink current.

I was concerned after reading various user burn their chips but didn't get the details of why.
I had one TLC that overheated during a breadboard test but it was only using 3 channels and an R_Iref of 6.8K to give about 5.7mA sink current per channel, thinking that this was a very safe starting condition. I suspected it was a defective chip from one of those "$1 each vendor". A replacement TLC ran cool with no heating at all, and ran just fine for the same 3 channels. But my confidence was shaken with regards how to interpret the datasheet. The dip version can dissipate 1.5watts with an ambient TA=70 C, which implies (to me at least) a full 120mA sink current on all channels.

Edit:
I could load each channel with a 47 ohm resistor and use a 10K pot for R_Iref and slowly lower the pot value while monitoring the chip temperature and see what happens. :)
 
Last edited:
LightUp,
Thanks for verifying this data. I'll work on laying out my new board and give it a test run as time allows over the next couple of weeks.

Keith
 
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