High Voltage Shift Register Outputs 50V?

Other Hardware General Electronics
1

I am using the TPIC6B595 instead of the 74HC595 specifically because the TPIC allows higher voltages, or at least that is what I thought. Now I am looking at the data sheet and it lists that the logic supply voltage is only 7V (I am using a component that requires 32). I originally thought I could pipe my 36V through the chips Vcc in.

To add to the confusion, there is a listing stating that the component has a "Output clamp voltage VDS" of 50V. Later on the paper describes it as "Power DMOS drain to source voltage Vds".

Does this mean that the circuit takes in a voltage less than 7V and outputs 50V, or does it take in an input less than 50V and also output 50V? For some background, I plan on using this register to control this 7 Segment display (Big Digit Seven-Segment LED displays). The registers spec sheet is at http://www.sparkfun.com/datasheets/IC/TPIC6B595.pdf. Also, I hope that the limited current output of teh register will save me the trouble of manually lowering the .7A of source current I have.

Here is how I plan to wire this up (roughly). I am pretty sure this is hugely wrong, and all I got right was the TPIC. I thing I will have to add some resistors along the red rail, but i am not sure =/

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I apologize if my ignorance appalls you. Any guidance would be greatly appreciated. Thanks =)

HUZZAH!

2

That chip sinks current, it does not source it. You supply it with the nomimal +5V supply and control it with normal TTL levels signals (0V,+5V) from the Arduino and feed the LEDs the up to +50V on the top side (LED anodes) and use the 595 "outputs" on the low side (LED cathodes) to sink that voltage. It will sink it (and light the LED), or not, depending on the state of the shift register. They are sinks, not sources. Look at the datasheet and notice the "inputs" are called "drains".

http://www.datasheetcatalog.org/datasheet/texasinstruments/tpic6b595.pdf

Don't forget the resistors! Am I blind, where are the resistors? Or does the funny symbol means a constant current constant voltage driver?

3

Thanks. So here is what I think the final circuit should look like: I added a 470 ohm resistor to the display power supply, and added the arduino's 5V supply to the shift register in.

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Thanks for the help
HUZZAH!