Replace TPIC6B595 with 74HC595 + ULN2803

[Alan69]

uln2803 pic clock thermostat

But of course much cheaper to use a 74hc595 and uln2003 setup, the ones with built in drivers tend to be more expensive and harder to find. No real need to use 2803s, just stagger the 7 to 8 relationship, 2003s are generally half the price of 2803s or less..

Alan

 

[Mike K8LH]

16 led sur 74hc595

I think I would go for the TPIC6C595 in a 16 pin package. Available at approximately $1.11 or $1.17 (single quantity) at Mouser. That's actually very close to the price of a 74HC595 and ULN2803 combination at $1.24 (single quantity) also at Mouser...

But I also wonder if you couldn't drive this non-multiplexed display sub-system with just plain old 74HC595 ICs ($0.44 single quantity) and limiting segment current to around 10 ma? Oops! Never mind. Just realized that the 74HC595 outputs aren't open collector or open drain and so that would limit your choice of source voltages on the LED common anodes.

Mike

 

[Alan69]

uln2803 replacement

Heck that's a lot better than the ~$5 each for the uln5895s last I checked. But they do more like 500 ma I think. $1 is pretty reasonable for that TPIC.

Most ACT outputs do like 50 ma max, so if someone has a 595 or similar serial to parallel in ACT it could do that fairly legitimately. Probably over package dissipation with all outputs doing that, but would probably work fine. Likely still $1 anyway, so may as well get the TPIC for new, but might find an ACT version surplus somewhere..

 

[hogges]

Hi,
I am looking at the same question for driving 100mA continuous current LEDs.

The TPIC6C595 seems at the very limit here, as the datasheet specifies continuous current for all eight outputs only at a case temperature of up to 25 degrees.

I drew up the attached schematic to use the suggestion of Alan69 of using individual transistors with an emitter follower. That's two transistors and two resistors per LED.

I would appreciate any comments to this (untested) schematic and the TPIC limitations for this application.

Best regards,
Wolfgang in Switzerland

 

[electronicus]

Can anyone modify software to display only the time?
Please help me.
Thank you.